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Refine Ribbon configuration, improve testing, add Homogeneous (#7879)

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Summary:
This change only affects non-schema-critical aspects of the production candidate Ribbon filter. Specifically, it refines choice of internal configuration parameters based on inputs. The changes are minor enough that the schema tests in bloom_test, some of which depend on this, are unaffected. There are also some minor optimizations and refactorings.

This would be a schema change for "smash" Ribbon, to fix some known issues with small filters, but "smash" Ribbon is not accessible in public APIs. Unit test CompactnessAndBacktrackAndFpRate updated to test small and medium-large filters. Run with --thoroughness=100 or so for much better detection power (not appropriate for continuous regression testing).

Homogenous Ribbon:
This change adds internally a Ribbon filter variant we call Homogeneous Ribbon, in collaboration with Stefan Walzer. The expected "result" value for every key is zero, instead of computed from a hash. Entropy for queries not to be false positives comes from free variables ("overhead") in the solution structure, which are populated pseudorandomly. Construction is slightly faster for not tracking result values, and never fails. Instead, FP rate can jump up whenever and whereever entries are packed too tightly. For small structures, we can choose overhead to make this FP rate jump unlikely, as seen in updated unit test CompactnessAndBacktrackAndFpRate.

Unlike standard Ribbon, Homogeneous Ribbon seems to scale to arbitrary number of keys when accepting an FP rate penalty for small pockets of high FP rate in the structure. For example, 64-bit ribbon with 8 solution columns and 10% allocated space overhead for slots seems to achieve about 10.5% space overhead vs. information-theoretic minimum based on its observed FP rate with expected pockets of degradation. (FP rate is close to 1/256.) If targeting a higher FP rate with fewer solution columns, Homogeneous Ribbon can be even more space efficient, because the penalty from degradation is relatively smaller. If targeting a lower FP rate, Homogeneous Ribbon is less space efficient, as more allocated overhead is needed to keep the FP rate impact of degradation relatively under control. The new OptimizeHomogAtScale tool in ribbon_test helps to find these optimal allocation overheads for different numbers of solution columns. And Ribbon widths, with 128-bit Ribbon apparently cutting space overheads in half vs. 64-bit.

Other misc item specifics:
* Ribbon APIs in util/ribbon_config.h now provide configuration data for not just 5% construction failure rate (95% success), but also 50% and 0.1%.
  * Note that the Ribbon structure does not exhibit "threshold" behavior as standard Xor filter does, so there is a roughly fixed space penalty to cut construction failure rate in half. Thus, there isn't really an "almost sure" setting.
  * Although we can extrapolate settings for large filters, we don't have a good formula for configuring smaller filters (< 2^17 slots or so), and efforts to summarize with a formula have failed. Thus, small data is hard-coded from updated FindOccupancy tool.
* Enhances ApproximateNumEntries for public API Ribbon using more precise data (new API GetNumToAdd), thus a more accurate but not perfect reversal of CalculateSpace. (bloom_test updated to expect the greater precision)
* Move EndianSwapValue from coding.h to coding_lean.h to keep Ribbon code easily transferable from RocksDB
* Add some missing 'const' to member functions
* Small optimization to 128-bit BitParity
* Small refactoring of BandingStorage in ribbon_alg.h to support Homogeneous Ribbon
* CompactnessAndBacktrackAndFpRate now has an "expand" test: on construction failure, a possible alternative to re-seeding hash functions is simply to increase the number of slots (allocated space overhead) and try again with essentially the same hash values. (Start locations will be different roundings of the same scaled hash values--because fastrange not mod.) This seems to be as effective or more effective than re-seeding, as long as we increase the number of slots (m) by roughly m += m/w where w is the Ribbon width. This way, there is effectively an expansion by one slot for each ribbon-width window in the banding. (This approach assumes that getting "bad data" from your hash function is as unlikely as it naturally should be, e.g. no adversary.)
* 32-bit and 16-bit Ribbon configurations are added to ribbon_test for understanding their behavior, e.g. with FindOccupancy. They are not considered useful at this time and not tested with CompactnessAndBacktrackAndFpRate.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7879

Test Plan: unit test updates included

Reviewed By: jay-zhuang

Differential Revision: D26371245

Pulled By: pdillinger

fbshipit-source-id: da6600d90a3785b99ad17a88b2a3027710b4ea3a
This commit is contained in:
Peter Dillinger 2021-02-26 08:48:55 -08:00 committed by Facebook GitHub Bot
parent c370d8aa12
commit a8b3b9a20c
13 changed files with 1604 additions and 499 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
CMakeLists.txt
View File

@ -766,6 +766,7 @@ set(SOURCES
util/murmurhash.cc
util/random.cc
util/rate_limiter.cc
util/ribbon_config.cc
util/slice.cc
util/file_checksum_helper.cc
util/status.cc

2
TARGETS
View File

@ -342,6 +342,7 @@ cpp_library(
"util/murmurhash.cc",
"util/random.cc",
"util/rate_limiter.cc",
"util/ribbon_config.cc",
"util/slice.cc",
"util/status.cc",
"util/string_util.cc",
@ -647,6 +648,7 @@ cpp_library(
"util/murmurhash.cc",
"util/random.cc",
"util/rate_limiter.cc",
"util/ribbon_config.cc",
"util/slice.cc",
"util/status.cc",
"util/string_util.cc",

1
src.mk
View File

@ -208,6 +208,7 @@ LIB_SOURCES = \
util/murmurhash.cc \
util/random.cc \
util/rate_limiter.cc \
util/ribbon_config.cc \
util/slice.cc \
util/file_checksum_helper.cc \
util/status.cc \

15
table/block_based/filter_policy.cc
View File

@ -21,6 +21,7 @@
#include "util/bloom_impl.h"
#include "util/coding.h"
#include "util/hash.h"
#include "util/ribbon_config.h"
#include "util/ribbon_impl.h"
namespace ROCKSDB_NAMESPACE {
@ -399,6 +400,7 @@ struct Standard128RibbonRehasherTypesAndSettings {
// These are schema-critical. Any change almost certainly changes
// underlying data.
static constexpr bool kIsFilter = true;
static constexpr bool kHomogeneous = false;
static constexpr bool kFirstCoeffAlwaysOne = true;
static constexpr bool kUseSmash = false;
using CoeffRow = ROCKSDB_NAMESPACE::Unsigned128;
@ -598,8 +600,7 @@ class Standard128RibbonBitsBuilder : public XXH3pFilterBitsBuilder {
// Let's not bother accounting for overflow to Bloom filter
// (Includes NaN case)
if (!(max_slots <
BandingType::GetNumSlotsFor95PctSuccess(kMaxRibbonEntries))) {
if (!(max_slots < ConfigHelper::GetNumSlots(kMaxRibbonEntries))) {
return kMaxRibbonEntries;
}
@ -628,12 +629,7 @@ class Standard128RibbonBitsBuilder : public XXH3pFilterBitsBuilder {
slots = SolnType::RoundDownNumSlots(slots - 1);
}
// Using slots instead of entries to get overhead factor estimate
double f = BandingType::GetFactorFor95PctSuccess(slots);
uint32_t num_entries = static_cast<uint32_t>(slots / f);
// Improve precision with another round
f = BandingType::GetFactorFor95PctSuccess(num_entries);
num_entries = static_cast<uint32_t>(slots / f + 0.999999999);
uint32_t num_entries = ConfigHelper::GetNumToAdd(slots);
// Consider possible Bloom fallback for small filters
if (slots < 1024) {
@ -675,9 +671,10 @@ class Standard128RibbonBitsBuilder : public XXH3pFilterBitsBuilder {
using TS = Standard128RibbonTypesAndSettings;
using SolnType = ribbon::SerializableInterleavedSolution<TS>;
using BandingType = ribbon::StandardBanding<TS>;
using ConfigHelper = ribbon::BandingConfigHelper1TS<ribbon::kOneIn20, TS>;
static uint32_t NumEntriesToNumSlots(uint32_t num_entries) {
uint32_t num_slots1 = BandingType::GetNumSlotsFor95PctSuccess(num_entries);
uint32_t num_slots1 = ConfigHelper::GetNumSlots(num_entries);
return SolnType::RoundUpNumSlots(num_slots1);
}

4
util/bloom_test.cc
View File

@ -431,10 +431,10 @@ TEST_P(FullBloomTest, FilterSize) {
size_t n2 = bits_builder->ApproximateNumEntries(space);
EXPECT_GE(n2, n);
size_t space2 = bits_builder->CalculateSpace(n2);
if (n > 6000 && GetParam() == BloomFilterPolicy::kStandard128Ribbon) {
if (n > 12000 && GetParam() == BloomFilterPolicy::kStandard128Ribbon) {
// TODO(peterd): better approximation?
EXPECT_GE(space2, space);
EXPECT_LE(space2 * 0.98 - 16.0, space * 1.0);
EXPECT_LE(space2 * 0.998, space * 1.0);
} else {
EXPECT_EQ(space2, space);
}

32
util/coding.h
View File

@ -320,38 +320,6 @@ inline bool GetVarsignedint64(Slice* input, int64_t* value) {
}
}
// Swaps between big and little endian. Can be used to in combination
// with the little-endian encoding/decoding functions to encode/decode
// big endian.
template <typename T>
inline T EndianSwapValue(T v) {
static_assert(std::is_integral<T>::value, "non-integral type");
#ifdef _MSC_VER
if (sizeof(T) == 2) {
return static_cast<T>(_byteswap_ushort(static_cast<uint16_t>(v)));
} else if (sizeof(T) == 4) {
return static_cast<T>(_byteswap_ulong(static_cast<uint32_t>(v)));
} else if (sizeof(T) == 8) {
return static_cast<T>(_byteswap_uint64(static_cast<uint64_t>(v)));
}
#else
if (sizeof(T) == 2) {
return static_cast<T>(__builtin_bswap16(static_cast<uint16_t>(v)));
} else if (sizeof(T) == 4) {
return static_cast<T>(__builtin_bswap32(static_cast<uint32_t>(v)));
} else if (sizeof(T) == 8) {
return static_cast<T>(__builtin_bswap64(static_cast<uint64_t>(v)));
}
#endif
// Recognized by clang as bswap, but not by gcc :(
T ret_val = 0;
for (size_t i = 0; i < sizeof(T); ++i) {
ret_val |= ((v >> (8 * i)) & 0xff) << (8 * (sizeof(T) - 1 - i));
}
return ret_val;
}
inline bool GetLengthPrefixedSlice(Slice* input, Slice* result) {
uint32_t len = 0;
if (GetVarint32(input, &len) && input->size() >= len) {

32
util/coding_lean.h
View File

@ -98,4 +98,36 @@ inline uint64_t DecodeFixed64(const char* ptr) {
}
}
// Swaps between big and little endian. Can be used to in combination
// with the little-endian encoding/decoding functions to encode/decode
// big endian.
template <typename T>
inline T EndianSwapValue(T v) {
static_assert(std::is_integral<T>::value, "non-integral type");
#ifdef _MSC_VER
if (sizeof(T) == 2) {
return static_cast<T>(_byteswap_ushort(static_cast<uint16_t>(v)));
} else if (sizeof(T) == 4) {
return static_cast<T>(_byteswap_ulong(static_cast<uint32_t>(v)));
} else if (sizeof(T) == 8) {
return static_cast<T>(_byteswap_uint64(static_cast<uint64_t>(v)));
}
#else
if (sizeof(T) == 2) {
return static_cast<T>(__builtin_bswap16(static_cast<uint16_t>(v)));
} else if (sizeof(T) == 4) {
return static_cast<T>(__builtin_bswap32(static_cast<uint32_t>(v)));
} else if (sizeof(T) == 8) {
return static_cast<T>(__builtin_bswap64(static_cast<uint64_t>(v)));
}
#endif
// Recognized by clang as bswap, but not by gcc :(
T ret_val = 0;
for (size_t i = 0; i < sizeof(T); ++i) {
ret_val |= ((v >> (8 * i)) & 0xff) << (8 * (sizeof(T) - 1 - i));
}
return ret_val;
}
} // namespace ROCKSDB_NAMESPACE

2
util/math128.h
View File

@ -215,7 +215,7 @@ inline int BitsSetToOne(Unsigned128 v) {
template <>
inline int BitParity(Unsigned128 v) {
return BitParity(Lower64of128(v)) ^ BitParity(Upper64of128(v));
return BitParity(Lower64of128(v) ^ Upper64of128(v));
}
template <typename T>

51
util/ribbon_alg.h
View File

@ -8,6 +8,7 @@
#include <array>
#include <memory>
#include "rocksdb/rocksdb_namespace.h"
#include "util/math128.h"
namespace ROCKSDB_NAMESPACE {
@ -501,12 +502,13 @@ namespace ribbon {
// // slot index i.
// void Prefetch(Index i) const;
//
// // Returns a pointer to CoeffRow for slot index i.
// CoeffRow* CoeffRowPtr(Index i);
//
// // Returns a pointer to ResultRow for slot index i. (Gaussian row
// // operations involve both side of the equation.)
// ResultRow* ResultRowPtr(Index i);
// // Load or store CoeffRow and ResultRow for slot index i.
// // (Gaussian row operations involve both sides of the equation.)
// // Bool `for_back_subst` indicates that customizing values for
// // unconstrained solution rows (cr == 0) is allowed.
// void LoadRow(Index i, CoeffRow *cr, ResultRow *rr, bool for_back_subst)
// const;
// void StoreRow(Index i, CoeffRow cr, ResultRow rr);
//
// // Returns the number of columns that can start an r-sequence of
// // coefficients, which is the number of slots minus r (kCoeffBits)
@ -548,6 +550,7 @@ bool BandingAdd(BandingStorage *bs, typename BandingStorage::Index start,
typename BandingStorage::CoeffRow cr, BacktrackStorage *bts,
typename BandingStorage::Index *backtrack_pos) {
using CoeffRow = typename BandingStorage::CoeffRow;
using ResultRow = typename BandingStorage::ResultRow;
using Index = typename BandingStorage::Index;
Index i = start;
@ -561,18 +564,19 @@ bool BandingAdd(BandingStorage *bs, typename BandingStorage::Index start,
for (;;) {
assert((cr & 1) == 1);
CoeffRow other = *(bs->CoeffRowPtr(i));
if (other == 0) {
*(bs->CoeffRowPtr(i)) = cr;
*(bs->ResultRowPtr(i)) = rr;
CoeffRow cr_at_i;
ResultRow rr_at_i;
bs->LoadRow(i, &cr_at_i, &rr_at_i, /* for_back_subst */ false);
if (cr_at_i == 0) {
bs->StoreRow(i, cr, rr);
bts->BacktrackPut(*backtrack_pos, i);
++*backtrack_pos;
return true;
}
assert((other & 1) == 1);
assert((cr_at_i & 1) == 1);
// Gaussian row reduction
cr ^= other;
rr ^= *(bs->ResultRowPtr(i));
cr ^= cr_at_i;
rr ^= rr_at_i;
if (cr == 0) {
// Inconsistency or (less likely) redundancy
break;
@ -678,12 +682,11 @@ bool BandingAddRange(BandingStorage *bs, BacktrackStorage *bts,
while (backtrack_pos > 0) {
--backtrack_pos;
Index i = bts->BacktrackGet(backtrack_pos);
*(bs->CoeffRowPtr(i)) = 0;
// Not strictly required, but is required for good FP rate on
// inputs that might have been backtracked out. (We don't want
// anything we've backtracked on to leak into final result, as
// that might not be "harmless".)
*(bs->ResultRowPtr(i)) = 0;
// Clearing the ResultRow is not strictly required, but is required
// for good FP rate on inputs that might have been backtracked out.
// (We don't want anything we've backtracked on to leak into final
// result, as that might not be "harmless".)
bs->StoreRow(i, 0, 0);
}
}
return false;
@ -780,8 +783,9 @@ void SimpleBackSubst(SimpleSolutionStorage *sss, const BandingStorage &bs) {
for (Index i = num_slots; i > 0;) {
--i;
CoeffRow cr = *const_cast<BandingStorage &>(bs).CoeffRowPtr(i);
ResultRow rr = *const_cast<BandingStorage &>(bs).ResultRowPtr(i);
CoeffRow cr;
ResultRow rr;
bs.LoadRow(i, &cr, &rr, /* for_back_subst */ true);
// solution row
ResultRow sr = 0;
for (Index j = 0; j < kResultBits; ++j) {
@ -976,8 +980,9 @@ inline void BackSubstBlock(typename BandingStorage::CoeffRow *state,
for (Index i = start_slot + kCoeffBits; i > start_slot;) {
--i;
CoeffRow cr = *const_cast<BandingStorage &>(bs).CoeffRowPtr(i);
ResultRow rr = *const_cast<BandingStorage &>(bs).ResultRowPtr(i);
CoeffRow cr;
ResultRow rr;
bs.LoadRow(i, &cr, &rr, /* for_back_subst */ true);
for (Index j = 0; j < num_columns; ++j) {
// Compute next solution bit at row i, column j (see derivation below)
CoeffRow tmp = state[j] << 1;

506
util/ribbon_config.cc Normal file
View File

@ -0,0 +1,506 @@
// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#include "util/ribbon_config.h"
namespace ROCKSDB_NAMESPACE {
namespace ribbon {
namespace detail {
// Each instantiation of this struct is sufficiently unique for configuration
// purposes, and is only instantiated for settings where we support the
// configuration API. An application might only reference one instantiation,
// meaning the rest could be pruned at link time.
template <ConstructionFailureChance kCfc, uint64_t kCoeffBits, bool kUseSmash>
struct BandingConfigHelperData {
static constexpr size_t kKnownSize = 18U;
// Because of complexity in the data, for smaller numbers of slots
// (powers of two up to 2^17), we record known numbers that can be added
// with kCfc chance of construction failure and settings in template
// parameters. Zero means "unsupported (too small) number of slots".
// (GetNumToAdd below will use interpolation for numbers of slots
// between powers of two; double rather than integer values here make
// that more accurate.)
static const std::array<double, kKnownSize> kKnownToAddByPow2;
// For sufficiently large number of slots, doubling the number of
// slots will increase the expected overhead (slots over number added)
// by approximately this constant.
// (This is roughly constant regardless of ConstructionFailureChance and
// smash setting.)
// (Would be a constant if we had partial template specialization for
// static const members.)
static inline double GetFactorPerPow2() {
if (kCoeffBits == 128U) {
return 0.0038;
} else {
assert(kCoeffBits == 64U);
return 0.0083;
}
}
// Overhead factor for 2^(kKnownSize-1) slots
// (Would be a constant if we had partial template specialization for
// static const members.)
static inline double GetFinalKnownFactor() {
return 1.0 * (uint32_t{1} << (kKnownSize - 1)) /
kKnownToAddByPow2[kKnownSize - 1];
}
// GetFinalKnownFactor() - (kKnownSize-1) * GetFactorPerPow2()
// (Would be a constant if we had partial template specialization for
// static const members.)
static inline double GetBaseFactor() {
return GetFinalKnownFactor() - (kKnownSize - 1) * GetFactorPerPow2();
}
// Get overhead factor (slots over number to add) for sufficiently large
// number of slots (by log base 2)
static inline double GetFactorForLarge(double log2_num_slots) {
return GetBaseFactor() + log2_num_slots * GetFactorPerPow2();
}
// For a given power of two number of slots (specified by whole number
// log base 2), implements GetNumToAdd for such limited case, returning
// double for better interpolation in GetNumToAdd and GetNumSlots.
static inline double GetNumToAddForPow2(uint32_t log2_num_slots) {
assert(log2_num_slots <= 32); // help clang-analyze
if (log2_num_slots < kKnownSize) {
return kKnownToAddByPow2[log2_num_slots];
} else {
return 1.0 * (uint64_t{1} << log2_num_slots) /
GetFactorForLarge(1.0 * log2_num_slots);
}
}
};
// Based on data from FindOccupancy in ribbon_test
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn2, 128U, false>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0,
0, // unsupported
252.984,
506.109,
1013.71,
2029.47,
4060.43,
8115.63,
16202.2,
32305.1,
64383.5,
128274,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn2, 128U, /*smash*/ true>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0, // unsupported
126.274,
254.279,
510.27,
1022.24,
2046.02,
4091.99,
8154.98,
16244.3,
32349.7,
64426.6,
128307,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn2, 64U, false>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0, // unsupported
124.94,
249.968,
501.234,
1004.06,
2006.15,
3997.89,
7946.99,
15778.4,
31306.9,
62115.3,
123284,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn2, 64U, /*smash*/ true>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0, // unsupported
62.2683,
126.259,
254.268,
509.975,
1019.98,
2026.16,
4019.75,
7969.8,
15798.2,
31330.3,
62134.2,
123255,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn20, 128U, false>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0,
0, // unsupported
248.851,
499.532,
1001.26,
2003.97,
4005.59,
8000.39,
15966.6,
31828.1,
63447.3,
126506,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn20, 128U, /*smash*/ true>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0, // unsupported
122.637,
250.651,
506.625,
1018.54,
2036.43,
4041.6,
8039.25,
16005,
31869.6,
63492.8,
126537,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn20, 64U, false>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0, // unsupported
120.659,
243.346,
488.168,
976.373,
1948.86,
3875.85,
7704.97,
15312.4,
30395.1,
60321.8,
119813,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn20, 64U, /*smash*/ true>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0, // unsupported
58.6016,
122.619,
250.641,
503.595,
994.165,
1967.36,
3898.17,
7727.21,
15331.5,
30405.8,
60376.2,
119836,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn1000, 128U, false>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0,
0, // unsupported
242.61,
491.887,
983.603,
1968.21,
3926.98,
7833.99,
15629,
31199.9,
62307.8,
123870,
}};
template <>
const std::array<double, 18> BandingConfigHelperData<
kOneIn1000, 128U, /*smash*/ true>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0, // unsupported
117.19,
245.105,
500.748,
1010.67,
1993.4,
3950.01,
7863.31,
15652,
31262.1,
62462.8,
124095,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn1000, 64U, false>::kKnownToAddByPow2{{
0,
0,
0,
0,
0,
0,
0, // unsupported
114,
234.8,
471.498,
940.165,
1874,
3721.5,
7387.5,
14592,
29160,
57745,
115082,
}};
template <>
const std::array<double, 18>
BandingConfigHelperData<kOneIn1000, 64U, /*smash*/ true>::kKnownToAddByPow2{
{
0,
0,
0,
0,
0,
0, // unsupported
53.0434,
117,
245.312,
483.571,
950.251,
1878,
3736.34,
7387.97,
14618,
29142.9,
57838.8,
114932,
}};
// We hide these implementation details from the .h file with explicit
// instantiations below these partial specializations.
template <ConstructionFailureChance kCfc, uint64_t kCoeffBits, bool kUseSmash,
bool kHomogeneous>
uint32_t BandingConfigHelper1MaybeSupported<
kCfc, kCoeffBits, kUseSmash, kHomogeneous,
true /* kIsSupported */>::GetNumToAdd(uint32_t num_slots) {
using Data = detail::BandingConfigHelperData<kCfc, kCoeffBits, kUseSmash>;
if (num_slots == 0) {
return 0;
}
uint32_t num_to_add;
double log2_num_slots = std::log(num_slots) * 1.4426950409;
uint32_t floor_log2 = static_cast<uint32_t>(log2_num_slots);
if (floor_log2 + 1 < Data::kKnownSize) {
double ceil_portion = 1.0 * num_slots / (uint32_t{1} << floor_log2) - 1.0;
// Must be a supported number of slots
assert(Data::kKnownToAddByPow2[floor_log2] > 0.0);
// Weighted average of two nearest known data points
num_to_add = static_cast<uint32_t>(
ceil_portion * Data::kKnownToAddByPow2[floor_log2 + 1] +
(1.0 - ceil_portion) * Data::kKnownToAddByPow2[floor_log2]);
} else {
// Use formula for large values
double factor = Data::GetFactorForLarge(log2_num_slots);
assert(factor >= 1.0);
num_to_add = static_cast<uint32_t>(num_slots / factor);
}
if (kHomogeneous) {
// Even when standard filter construction would succeed, we might
// have loaded things up too much for Homogeneous filter. (Complete
// explanation not known but observed empirically.) This seems to
// correct for that, mostly affecting small filter configurations.
if (num_to_add >= 8) {
num_to_add -= 8;
} else {
assert(false);
}
}
return num_to_add;
}
template <ConstructionFailureChance kCfc, uint64_t kCoeffBits, bool kUseSmash,
bool kHomogeneous>
uint32_t BandingConfigHelper1MaybeSupported<
kCfc, kCoeffBits, kUseSmash, kHomogeneous,
true /* kIsSupported */>::GetNumSlots(uint32_t num_to_add) {
using Data = detail::BandingConfigHelperData<kCfc, kCoeffBits, kUseSmash>;
if (num_to_add == 0) {
return 0;
}
if (kHomogeneous) {
// Reverse of above in GetNumToAdd
num_to_add += 8;
}
double log2_num_to_add = std::log(num_to_add) * 1.4426950409;
uint32_t approx_log2_slots = static_cast<uint32_t>(log2_num_to_add + 0.5);
assert(approx_log2_slots <= 32); // help clang-analyze
double lower_num_to_add = Data::GetNumToAddForPow2(approx_log2_slots);
double upper_num_to_add;
if (approx_log2_slots == 0 || lower_num_to_add == /* unsupported */ 0) {
// Return minimum non-zero slots in standard implementation
return kUseSmash ? kCoeffBits : 2 * kCoeffBits;
} else if (num_to_add < lower_num_to_add) {
upper_num_to_add = lower_num_to_add;
--approx_log2_slots;
lower_num_to_add = Data::GetNumToAddForPow2(approx_log2_slots);
} else {
upper_num_to_add = Data::GetNumToAddForPow2(approx_log2_slots + 1);
}
assert(num_to_add >= lower_num_to_add);
assert(num_to_add < upper_num_to_add);
double upper_portion =
(num_to_add - lower_num_to_add) / (upper_num_to_add - lower_num_to_add);
double lower_num_slots = 1.0 * (uint64_t{1} << approx_log2_slots);
// Interpolation, round up
return static_cast<uint32_t>(upper_portion * lower_num_slots +
lower_num_slots + 0.999999999);
}
// These explicit instantiations enable us to hide most of the
// implementation details from the .h file. (The .h file currently
// needs to determine whether settings are "supported" or not.)
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 128U, /*sm*/ false,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 128U, /*sm*/ true,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 128U, /*sm*/ false,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 128U, /*sm*/ true,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 64U, /*sm*/ false,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 64U, /*sm*/ true,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 64U, /*sm*/ false,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn2, 64U, /*sm*/ true,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 128U, /*sm*/ false,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 128U, /*sm*/ true,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 128U, /*sm*/ false,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 128U, /*sm*/ true,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 64U, /*sm*/ false,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 64U, /*sm*/ true,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 64U, /*sm*/ false,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn20, 64U, /*sm*/ true,
/*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<
kOneIn1000, 128U, /*sm*/ false, /*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<
kOneIn1000, 128U, /*sm*/ true, /*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<
kOneIn1000, 128U, /*sm*/ false, /*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<
kOneIn1000, 128U, /*sm*/ true, /*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<
kOneIn1000, 64U, /*sm*/ false, /*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn1000, 64U, /*sm*/ true,
/*hm*/ false, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<
kOneIn1000, 64U, /*sm*/ false, /*hm*/ true, /*sup*/ true>;
template struct BandingConfigHelper1MaybeSupported<kOneIn1000, 64U, /*sm*/ true,
/*hm*/ true, /*sup*/ true>;
} // namespace detail
} // namespace ribbon
} // namespace ROCKSDB_NAMESPACE

182
util/ribbon_config.h Normal file
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@ -0,0 +1,182 @@
// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <array>
#include <cassert>
#include <cmath>
#include <cstdint>
#include "port/lang.h" // for FALLTHROUGH_INTENDED
#include "rocksdb/rocksdb_namespace.h"
namespace ROCKSDB_NAMESPACE {
namespace ribbon {
// RIBBON PHSF & RIBBON Filter (Rapid Incremental Boolean Banding ON-the-fly)
//
// ribbon_config.h: APIs for relating numbers of slots with numbers of
// additions for tolerable construction failure probabilities. This is
// separate from ribbon_impl.h because it might not be needed for
// some applications.
//
// This API assumes uint32_t for number of slots, as a single Ribbon
// linear system should not normally overflow that without big penalties.
//
// Template parameter kCoeffBits uses uint64_t for convenience in case it
// comes from size_t.
//
// Most of the complexity here is trying to optimize speed and
// compiled code size, using templates to minimize table look-ups and
// the compiled size of all linked look-up tables. Look-up tables are
// required because we don't have good formulas, and the data comes
// from running FindOccupancy in ribbon_test.
// Represents a chosen chance of successful Ribbon construction for a single
// seed. Allowing higher chance of failed construction can reduce space
// overhead but takes extra time in construction.
enum ConstructionFailureChance {
kOneIn2,
kOneIn20,
// When using kHomogeneous==true, construction failure chance should
// not generally exceed target FP rate, so it unlikely useful to
// allow a higher "failure" chance. In some cases, even more overhead
// is appropriate. (TODO)
kOneIn1000,
};
namespace detail {
// It is useful to compile ribbon_test linking to BandingConfigHelper with
// settings for which we do not have configuration data, as long as we don't
// run the code. This template hack supports that.
template <ConstructionFailureChance kCfc, uint64_t kCoeffBits, bool kUseSmash,
bool kHomogeneous, bool kIsSupported>
struct BandingConfigHelper1MaybeSupported {
public:
static uint32_t GetNumToAdd(uint32_t num_slots) {
// Unsupported
assert(num_slots == 0);
(void)num_slots;
return 0;
}
static uint32_t GetNumSlots(uint32_t num_to_add) {
// Unsupported
assert(num_to_add == 0);
(void)num_to_add;
return 0;
}
};
// Base class for BandingConfigHelper1 and helper for BandingConfigHelper
// with core implementations built on above data
template <ConstructionFailureChance kCfc, uint64_t kCoeffBits, bool kUseSmash,
bool kHomogeneous>
struct BandingConfigHelper1MaybeSupported<
kCfc, kCoeffBits, kUseSmash, kHomogeneous, true /* kIsSupported */> {
public:
// See BandingConfigHelper1. Implementation in ribbon_config.cc
static uint32_t GetNumToAdd(uint32_t num_slots);
// See BandingConfigHelper1. Implementation in ribbon_config.cc
static uint32_t GetNumSlots(uint32_t num_to_add);
};
} // namespace detail
template <ConstructionFailureChance kCfc, uint64_t kCoeffBits, bool kUseSmash,
bool kHomogeneous>
struct BandingConfigHelper1
: public detail::BandingConfigHelper1MaybeSupported<
kCfc, kCoeffBits, kUseSmash, kHomogeneous,
/* kIsSupported */ kCoeffBits == 64 || kCoeffBits == 128> {
public:
// Returns a number of entries that can be added to a given number of
// slots, with roughly kCfc chance of construction failure per seed,
// or better. Does NOT do rounding for InterleavedSoln; call
// RoundUpNumSlots for that.
//
// inherited:
// static uint32_t GetNumToAdd(uint32_t num_slots);
// Returns a number of slots for a given number of entries to add
// that should have roughly kCfc chance of construction failure per
// seed, or better. Does NOT do rounding for InterleavedSoln; call
// RoundUpNumSlots for that.
//
// num_to_add should not exceed roughly 2/3rds of the maximum value
// of the uint32_t type to avoid overflow.
//
// inherited:
// static uint32_t GetNumSlots(uint32_t num_to_add);
};
// Configured using TypesAndSettings as in ribbon_impl.h
template <ConstructionFailureChance kCfc, class TypesAndSettings>
struct BandingConfigHelper1TS
: public BandingConfigHelper1<
kCfc,
/* kCoeffBits */ sizeof(typename TypesAndSettings::CoeffRow) * 8U,
TypesAndSettings::kUseSmash, TypesAndSettings::kHomogeneous> {};
// Like BandingConfigHelper1TS except failure chance can be a runtime rather
// than compile time value.
template <class TypesAndSettings>
struct BandingConfigHelper {
public:
static constexpr ConstructionFailureChance kDefaultFailureChance =
TypesAndSettings::kHomogeneous ? kOneIn1000 : kOneIn20;
static uint32_t GetNumToAdd(
uint32_t num_slots,
ConstructionFailureChance max_failure = kDefaultFailureChance) {
switch (max_failure) {
default:
assert(false);
FALLTHROUGH_INTENDED;
case kOneIn20: {
using H1 = BandingConfigHelper1TS<kOneIn20, TypesAndSettings>;
return H1::GetNumToAdd(num_slots);
}
case kOneIn2: {
using H1 = BandingConfigHelper1TS<kOneIn2, TypesAndSettings>;
return H1::GetNumToAdd(num_slots);
}
case kOneIn1000: {
using H1 = BandingConfigHelper1TS<kOneIn1000, TypesAndSettings>;
return H1::GetNumToAdd(num_slots);
}
}
}
static uint32_t GetNumSlots(
uint32_t num_to_add,
ConstructionFailureChance max_failure = kDefaultFailureChance) {
switch (max_failure) {
default:
assert(false);
FALLTHROUGH_INTENDED;
case kOneIn20: {
using H1 = BandingConfigHelper1TS<kOneIn20, TypesAndSettings>;
return H1::GetNumSlots(num_to_add);
}
case kOneIn2: {
using H1 = BandingConfigHelper1TS<kOneIn2, TypesAndSettings>;
return H1::GetNumSlots(num_to_add);
}
case kOneIn1000: {
using H1 = BandingConfigHelper1TS<kOneIn1000, TypesAndSettings>;
return H1::GetNumSlots(num_to_add);
}
}
}
};
} // namespace ribbon
} // namespace ROCKSDB_NAMESPACE

185
util/ribbon_impl.h
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@ -8,6 +8,7 @@
#include <cmath>
#include "port/port.h" // for PREFETCH
#include "util/fastrange.h"
#include "util/ribbon_alg.h"
namespace ROCKSDB_NAMESPACE {
@ -23,6 +24,8 @@ namespace ribbon {
// and core design details.
//
// TODO: more details on trade-offs and practical issues.
//
// APIs for configuring Ribbon are in ribbon_config.h
// Ribbon implementations in this file take these parameters, which must be
// provided in a class/struct type with members expressed in this concept:
@ -49,10 +52,22 @@ namespace ribbon {
// // construction.
// static constexpr bool kIsFilter;
//
// // When true, enables a special "homogeneous" filter implementation that
// // is slightly faster to construct, and never fails to construct though
// // FP rate can quickly explode in cases where corresponding
// // non-homogeneous filter would fail (or nearly fail?) to construct.
// // For smaller filters, you can configure with ConstructionFailureChance
// // smaller than desired FP rate to largely counteract this effect.
// // TODO: configuring Homogeneous Ribbon for arbitrarily large filters
// // based on data from OptimizeHomogAtScale
// static constexpr bool kHomogeneous;
//
// // When true, adds a tiny bit more hashing logic on queries and
// // construction to improve utilization at the beginning and end of
// // the structure. Recommended when CoeffRow is only 64 bits (or
// // less), so typical num_starts < 10k.
// // less), so typical num_starts < 10k. Although this is compatible
// // with kHomogeneous, the competing space vs. time priorities might
// // not be useful.
// static constexpr bool kUseSmash;
//
// // When true, allows number of "starts" to be zero, for best support
@ -201,7 +216,27 @@ class StandardHasher {
// This is not so much "critical path" code because it can be done in
// parallel (instruction level) with memory lookup.
//
// We do not need exhaustive remixing for CoeffRow, but just enough that
// When we might have many entries squeezed into a single start,
// we need reasonably good remixing for CoeffRow.
if (TypesAndSettings::kUseSmash) {
// Reasonably good, reasonably fast, reasonably general.
// Probably not 1:1 but probably close enough.
Unsigned128 a = Multiply64to128(h, kAltCoeffFactor1);
Unsigned128 b = Multiply64to128(h, kAltCoeffFactor2);
auto cr = static_cast<CoeffRow>(b ^ (a << 64) ^ (a >> 64));
// Now ensure the value is non-zero
if (kFirstCoeffAlwaysOne) {
cr |= 1;
} else {
// Still have to ensure some bit is non-zero
cr |= (cr == 0) ? 1 : 0;
}
return cr;
}
// If not kUseSmash, we ensure we're not squeezing many entries into a
// single start, in part by ensuring num_starts > num_slots / 2. Thus,
// here we do not need good remixing for CoeffRow, but just enough that
// (a) every bit is reasonably independent from Start.
// (b) every Hash-length bit subsequence of the CoeffRow has full or
// nearly full entropy from h.
@ -220,25 +255,27 @@ class StandardHasher {
// even with a (likely) different multiplier here.
Hash a = h * kCoeffAndResultFactor;
// If that's big enough, we're done. If not, we have to expand it,
// maybe up to 4x size.
uint64_t b = a;
static_assert(
sizeof(Hash) == sizeof(uint64_t) || sizeof(Hash) == sizeof(uint32_t),
"Supported sizes");
// If that's big enough, we're done. If not, we have to expand it,
// maybe up to 4x size.
uint64_t b;
if (sizeof(Hash) < sizeof(uint64_t)) {
// Almost-trivial hash expansion (OK - see above), favoring roughly
// equal number of 1's and 0's in result
b = (b << 32) ^ b ^ kCoeffXor32;
b = (uint64_t{a} << 32) ^ (a ^ kCoeffXor32);
} else {
b = a;
}
Unsigned128 c = b;
static_assert(sizeof(CoeffRow) == sizeof(uint64_t) ||
sizeof(CoeffRow) == sizeof(Unsigned128),
"Supported sizes");
static_assert(sizeof(CoeffRow) <= sizeof(Unsigned128), "Supported sizes");
Unsigned128 c;
if (sizeof(uint64_t) < sizeof(CoeffRow)) {
// Almost-trivial hash expansion (OK - see above), favoring roughly
// equal number of 1's and 0's in result
c = (c << 64) ^ c ^ kCoeffXor64;
c = (Unsigned128{b} << 64) ^ (b ^ kCoeffXor64);
} else {
c = b;
}
auto cr = static_cast<CoeffRow>(c);
@ -261,7 +298,7 @@ class StandardHasher {
return static_cast<ResultRow>(~ResultRow{0});
}
inline ResultRow GetResultRowFromHash(Hash h) const {
if (TypesAndSettings::kIsFilter) {
if (TypesAndSettings::kIsFilter && !TypesAndSettings::kHomogeneous) {
// This is not so much "critical path" code because it can be done in
// parallel (instruction level) with memory lookup.
//
@ -272,10 +309,9 @@ class StandardHasher {
// the same bits computed for CoeffRow, which are reasonably
// independent from Start. (Inlining and common subexpression
// elimination with GetCoeffRow should make this
// a single shared multiplication in generated code.)
//
// TODO: fix & test the kUseSmash case with very small num_starts
// a single shared multiplication in generated code when !kUseSmash.)
Hash a = h * kCoeffAndResultFactor;
// The bits here that are *most* independent of Start are the highest
// order bits (as in Knuth multiplicative hash). To make those the
// most preferred for use in the result row, we do a bswap here.
@ -337,6 +373,8 @@ class StandardHasher {
// large random prime
static constexpr Hash kCoeffAndResultFactor =
static_cast<Hash>(0xc28f82822b650bedULL);
static constexpr uint64_t kAltCoeffFactor1 = 0x876f170be4f1fcb9U;
static constexpr uint64_t kAltCoeffFactor2 = 0xf0433a4aecda4c5fU;
// random-ish data
static constexpr uint32_t kCoeffXor32 = 0xa6293635U;
static constexpr uint64_t kCoeffXor64 = 0xc367844a6e52731dU;
@ -447,17 +485,22 @@ class StandardBanding : public StandardHasher<TypesAndSettings> {
assert(num_slots >= kCoeffBits);
if (num_slots > num_slots_allocated_) {
coeff_rows_.reset(new CoeffRow[num_slots]());
if (!TypesAndSettings::kHomogeneous) {
// Note: don't strictly have to zero-init result_rows,
// except possible information leakage ;)
// except possible information leakage, etc ;)
result_rows_.reset(new ResultRow[num_slots]());
}
num_slots_allocated_ = num_slots;
} else {
for (Index i = 0; i < num_slots; ++i) {
coeff_rows_[i] = 0;
// Note: don't strictly have to zero-init result_rows
if (!TypesAndSettings::kHomogeneous) {
// Note: don't strictly have to zero-init result_rows,
// except possible information leakage, etc ;)
result_rows_[i] = 0;
}
}
}
num_starts_ = num_slots - kCoeffBits + 1;
}
EnsureBacktrackSize(backtrack_size);
@ -480,10 +523,32 @@ class StandardBanding : public StandardHasher<TypesAndSettings> {
}
inline void Prefetch(Index i) const {
PREFETCH(&coeff_rows_[i], 1 /* rw */, 1 /* locality */);
if (!TypesAndSettings::kHomogeneous) {
PREFETCH(&result_rows_[i], 1 /* rw */, 1 /* locality */);
}
inline CoeffRow* CoeffRowPtr(Index i) { return &coeff_rows_[i]; }
inline ResultRow* ResultRowPtr(Index i) { return &result_rows_[i]; }
}
inline void LoadRow(Index i, CoeffRow* cr, ResultRow* rr,
bool for_back_subst) const {
*cr = coeff_rows_[i];
if (TypesAndSettings::kHomogeneous) {
if (for_back_subst && *cr == 0) {
// Cheap pseudorandom data to fill unconstrained solution rows
*rr = static_cast<ResultRow>(i * 0x9E3779B185EBCA87ULL);
} else {
*rr = 0;
}
} else {
*rr = result_rows_[i];
}
}
inline void StoreRow(Index i, CoeffRow cr, ResultRow rr) {
coeff_rows_[i] = cr;
if (TypesAndSettings::kHomogeneous) {
assert(rr == 0);
} else {
result_rows_[i] = rr;
}
}
inline Index GetNumStarts() const { return num_starts_; }
// from concept BacktrackStorage, for when backtracking is used
@ -554,6 +619,10 @@ class StandardBanding : public StandardHasher<TypesAndSettings> {
return count;
}
// Returns whether a row is "occupied" in the banding (non-zero
// coefficients stored). (Only recommended for debug/test)
bool IsOccupied(Index i) { return coeff_rows_[i] != 0; }
// ********************************************************************
// High-level API
@ -608,54 +677,6 @@ class StandardBanding : public StandardHasher<TypesAndSettings> {
return false;
}
// ********************************************************************
// Static high-level API
// Based on data from FindOccupancyForSuccessRate in ribbon_test,
// returns a number of slots for a given number of entries to add
// that should have roughly 95% or better chance of successful
// construction per seed. Does NOT do rounding for InterleavedSoln;
// call RoundUpNumSlots for that.
//
// num_to_add should not exceed roughly 2/3rds of the maximum value
// of the Index type to avoid overflow.
static Index GetNumSlotsFor95PctSuccess(Index num_to_add) {
if (num_to_add == 0) {
return 0;
}
double factor = GetFactorFor95PctSuccess(num_to_add);
Index num_slots = static_cast<Index>(num_to_add * factor);
assert(num_slots >= num_to_add);
return num_slots;
}
// Based on data from FindOccupancyForSuccessRate in ribbon_test,
// given a number of entries to add, returns a space overhead factor
// (slots divided by num_to_add) that should have roughly 95% or better
// chance of successful construction per seed. Does NOT do rounding for
// InterleavedSoln; call RoundUpNumSlots for that.
//
// The reason that num_to_add is needed is that Ribbon filters of a
// particular CoeffRow size do not scale infinitely.
static double GetFactorFor95PctSuccess(Index num_to_add) {
double log2_num_to_add = std::log(num_to_add) * 1.442695;
if (kCoeffBits == 64) {
if (TypesAndSettings::kUseSmash) {
return 1.02 + std::max(log2_num_to_add - 8.5, 0.0) * 0.009;
} else {
return 1.05 + std::max(log2_num_to_add - 11.0, 0.0) * 0.009;
}
} else {
// Currently only support 64 and 128
assert(kCoeffBits == 128);
if (TypesAndSettings::kUseSmash) {
return 1.01 + std::max(log2_num_to_add - 10.0, 0.0) * 0.0042;
} else {
return 1.02 + std::max(log2_num_to_add - 12.0, 0.0) * 0.0042;
}
}
}
protected:
// TODO: explore combining in a struct
std::unique_ptr<CoeffRow[]> coeff_rows_;
@ -716,8 +737,8 @@ class InMemSimpleSolution {
}
template <typename PhsfQueryHasher>
ResultRow PhsfQuery(const Key& input, const PhsfQueryHasher& hasher) {
assert(!TypesAndSettings::kIsFilter);
ResultRow PhsfQuery(const Key& input, const PhsfQueryHasher& hasher) const {
// assert(!TypesAndSettings::kIsFilter); Can be useful in testing
if (TypesAndSettings::kAllowZeroStarts && num_starts_ == 0) {
// Unusual
return 0;
@ -728,7 +749,7 @@ class InMemSimpleSolution {
}
template <typename FilterQueryHasher>
bool FilterQuery(const Key& input, const FilterQueryHasher& hasher) {
bool FilterQuery(const Key& input, const FilterQueryHasher& hasher) const {
assert(TypesAndSettings::kIsFilter);
if (TypesAndSettings::kAllowZeroStarts && num_starts_ == 0) {
// Unusual. Zero starts presumes no keys added -> always false
@ -740,7 +761,7 @@ class InMemSimpleSolution {
}
}
double ExpectedFpRate() {
double ExpectedFpRate() const {
assert(TypesAndSettings::kIsFilter);
if (TypesAndSettings::kAllowZeroStarts && num_starts_ == 0) {
// Unusual, but we don't have FPs if we always return false.
@ -752,6 +773,20 @@ class InMemSimpleSolution {
return std::pow(0.5, 8U * sizeof(ResultRow));
}
// ********************************************************************
// Static high-level API
// Round up to a number of slots supported by this structure. Note that
// this needs to be must be taken into account for the banding if this
// solution layout/storage is to be used.
static Index RoundUpNumSlots(Index num_slots) {
// Must be at least kCoeffBits for at least one start
// Or if not smash, even more because hashing not equipped
// for stacking up so many entries on a single start location
auto min_slots = kCoeffBits * (TypesAndSettings::kUseSmash ? 1 : 2);
return std::max(num_slots, static_cast<Index>(min_slots));
}
protected:
// We generally store "starts" instead of slots for speed of GetStart(),
// as in StandardHasher.
@ -853,8 +888,8 @@ class SerializableInterleavedSolution {
}
template <typename PhsfQueryHasher>
ResultRow PhsfQuery(const Key& input, const PhsfQueryHasher& hasher) {
assert(!TypesAndSettings::kIsFilter);
ResultRow PhsfQuery(const Key& input, const PhsfQueryHasher& hasher) const {
// assert(!TypesAndSettings::kIsFilter); Can be useful in testing
if (TypesAndSettings::kAllowZeroStarts && num_starts_ == 0) {
// Unusual
return 0;
@ -873,7 +908,7 @@ class SerializableInterleavedSolution {
}
template <typename FilterQueryHasher>
bool FilterQuery(const Key& input, const FilterQueryHasher& hasher) {
bool FilterQuery(const Key& input, const FilterQueryHasher& hasher) const {
assert(TypesAndSettings::kIsFilter);
if (TypesAndSettings::kAllowZeroStarts && num_starts_ == 0) {
// Unusual. Zero starts presumes no keys added -> always false
@ -893,7 +928,7 @@ class SerializableInterleavedSolution {
}
}
double ExpectedFpRate() {
double ExpectedFpRate() const {
assert(TypesAndSettings::kIsFilter);
if (TypesAndSettings::kAllowZeroStarts && num_starts_ == 0) {
// Unusual. Zero starts presumes no keys added -> always false

642
util/ribbon_test.cc
View File

@ -3,48 +3,71 @@
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#include <cmath>
#include "rocksdb/system_clock.h"
#include "test_util/testharness.h"
#include "util/bloom_impl.h"
#include "util/coding.h"
#include "util/hash.h"
#include "util/ribbon_config.h"
#include "util/ribbon_impl.h"
#include "util/stop_watch.h"
#include "util/string_util.h"
#ifndef GFLAGS
uint32_t FLAGS_thoroughness = 5;
uint32_t FLAGS_max_add = 0;
uint32_t FLAGS_min_check = 4000;
uint32_t FLAGS_max_check = 100000;
bool FLAGS_verbose = false;
bool FLAGS_find_occ = false;
double FLAGS_find_next_factor = 1.414;
double FLAGS_find_success = 0.95;
double FLAGS_find_delta_start = 0.01;
double FLAGS_find_delta_end = 0.0001;
double FLAGS_find_delta_shrink = 0.99;
bool FLAGS_find_slot_occ = false;
double FLAGS_find_next_factor = 1.618;
uint32_t FLAGS_find_iters = 10000;
uint32_t FLAGS_find_min_slots = 128;
uint32_t FLAGS_find_max_slots = 12800000;
uint32_t FLAGS_find_max_slots = 1000000;
bool FLAGS_optimize_homog = false;
uint32_t FLAGS_optimize_homog_slots = 30000000;
uint32_t FLAGS_optimize_homog_check = 200000;
double FLAGS_optimize_homog_granularity = 0.002;
#else
#include "util/gflags_compat.h"
using GFLAGS_NAMESPACE::ParseCommandLineFlags;
// Using 500 is a good test when you have time to be thorough.
// Default is for general RocksDB regression test runs.
DEFINE_uint32(thoroughness, 5, "iterations per configuration");
DEFINE_uint32(max_add, 0,
"Add up to this number of entries to a single filter in "
"CompactnessAndBacktrackAndFpRate; 0 == reasonable default");
DEFINE_uint32(min_check, 4000,
"Minimum number of novel entries for testing FP rate");
DEFINE_uint32(max_check, 10000,
"Maximum number of novel entries for testing FP rate");
DEFINE_bool(verbose, false, "Print extra details");
// Options for FindOccupancy, which is more of a tool than a test.
DEFINE_bool(find_occ, false, "whether to run the FindOccupancy tool");
DEFINE_bool(find_slot_occ, false,
"whether to show individual slot occupancies with "
"FindOccupancy tool");
DEFINE_double(find_next_factor, 1.618,
"factor to next num_slots for FindOccupancy");
DEFINE_uint32(find_iters, 10000, "number of samples for FindOccupancy");
DEFINE_uint32(find_min_slots, 128, "number of slots for FindOccupancy");
DEFINE_uint32(find_max_slots, 1000000, "number of slots for FindOccupancy");
// Options for OptimizeHomogAtScale, which is more of a tool than a test.
DEFINE_bool(optimize_homog, false,
"whether to run the OptimizeHomogAtScale tool");
DEFINE_uint32(optimize_homog_slots, 30000000,
"number of slots for OptimizeHomogAtScale");
DEFINE_uint32(optimize_homog_check, 200000,
"number of queries for checking FP rate in OptimizeHomogAtScale");
DEFINE_double(
optimize_homog_granularity, 0.002,
"overhead change between FP rate checking in OptimizeHomogAtScale");
// Options for FindOccupancyForSuccessRate, which is more of a tool
// than a test.
DEFINE_bool(find_occ, false,
"whether to run the FindOccupancyForSuccessRate tool");
DEFINE_double(find_next_factor, 1.414,
"target success rate for FindOccupancyForSuccessRate");
DEFINE_double(find_success, 0.95,
"target success rate for FindOccupancyForSuccessRate");
DEFINE_double(find_delta_start, 0.01, " for FindOccupancyForSuccessRate");
DEFINE_double(find_delta_end, 0.0001, " for FindOccupancyForSuccessRate");
DEFINE_double(find_delta_shrink, 0.99, " for FindOccupancyForSuccessRate");
DEFINE_uint32(find_min_slots, 128,
"number of slots for FindOccupancyForSuccessRate");
DEFINE_uint32(find_max_slots, 12800000,
"number of slots for FindOccupancyForSuccessRate");
#endif // GFLAGS
template <typename TypesAndSettings>
@ -150,6 +173,18 @@ struct Hash64KeyGenWrapper : public KeyGen {
}
};
using ROCKSDB_NAMESPACE::ribbon::ConstructionFailureChance;
const std::vector<ConstructionFailureChance> kFailureOnly50Pct = {
ROCKSDB_NAMESPACE::ribbon::kOneIn2};
const std::vector<ConstructionFailureChance> kFailureOnlyRare = {
ROCKSDB_NAMESPACE::ribbon::kOneIn1000};
const std::vector<ConstructionFailureChance> kFailureAll = {
ROCKSDB_NAMESPACE::ribbon::kOneIn2, ROCKSDB_NAMESPACE::ribbon::kOneIn20,
ROCKSDB_NAMESPACE::ribbon::kOneIn1000};
} // namespace
using ROCKSDB_NAMESPACE::ribbon::ExpectedCollisionFpRate;
@ -164,6 +199,7 @@ struct DefaultTypesAndSettings {
using Seed = uint32_t;
using Key = ROCKSDB_NAMESPACE::Slice;
static constexpr bool kIsFilter = true;
static constexpr bool kHomogeneous = false;
static constexpr bool kFirstCoeffAlwaysOne = true;
static constexpr bool kUseSmash = false;
static constexpr bool kAllowZeroStarts = false;
@ -175,6 +211,9 @@ struct DefaultTypesAndSettings {
}
// For testing
using KeyGen = StandardKeyGen;
static const std::vector<ConstructionFailureChance>& FailureChanceToTest() {
return kFailureAll;
}
};
using TypesAndSettings_Coeff128 = DefaultTypesAndSettings;
@ -184,23 +223,58 @@ struct TypesAndSettings_Coeff128Smash : public DefaultTypesAndSettings {
struct TypesAndSettings_Coeff64 : public DefaultTypesAndSettings {
using CoeffRow = uint64_t;
};
struct TypesAndSettings_Coeff64Smash1 : public DefaultTypesAndSettings {
using CoeffRow = uint64_t;
struct TypesAndSettings_Coeff64Smash : public TypesAndSettings_Coeff64 {
static constexpr bool kUseSmash = true;
};
struct TypesAndSettings_Coeff64Smash0 : public TypesAndSettings_Coeff64Smash1 {
struct TypesAndSettings_Coeff64Smash0 : public TypesAndSettings_Coeff64Smash {
static constexpr bool kFirstCoeffAlwaysOne = false;
};
struct TypesAndSettings_Result16 : public DefaultTypesAndSettings {
// Homogeneous Ribbon configurations
struct TypesAndSettings_Coeff128_Homog : public DefaultTypesAndSettings {
static constexpr bool kHomogeneous = true;
// Since our best construction success setting still has 1/1000 failure
// rate, the best FP rate we test is 1/256
using ResultRow = uint8_t;
// Homogeneous only makes sense with sufficient slots for equivalent of
// almost sure construction success
static const std::vector<ConstructionFailureChance>& FailureChanceToTest() {
return kFailureOnlyRare;
}
};
struct TypesAndSettings_Coeff128Smash_Homog
: public TypesAndSettings_Coeff128_Homog {
// Smash (extra time to save space) + Homog (extra space to save time)
// doesn't make much sense in practice, but we minimally test it
static constexpr bool kUseSmash = true;
};
struct TypesAndSettings_Coeff64_Homog : public TypesAndSettings_Coeff128_Homog {
using CoeffRow = uint64_t;
};
struct TypesAndSettings_Coeff64Smash_Homog
: public TypesAndSettings_Coeff64_Homog {
// Smash (extra time to save space) + Homog (extra space to save time)
// doesn't make much sense in practice, but we minimally test it
static constexpr bool kUseSmash = true;
};
// Less exhaustive mix of coverage, but still covering the most stressful case
// (only 50% construction success)
struct AbridgedTypesAndSettings : public DefaultTypesAndSettings {
static const std::vector<ConstructionFailureChance>& FailureChanceToTest() {
return kFailureOnly50Pct;
}
};
struct TypesAndSettings_Result16 : public AbridgedTypesAndSettings {
using ResultRow = uint16_t;
};
struct TypesAndSettings_Result32 : public DefaultTypesAndSettings {
struct TypesAndSettings_Result32 : public AbridgedTypesAndSettings {
using ResultRow = uint32_t;
};
struct TypesAndSettings_IndexSizeT : public DefaultTypesAndSettings {
struct TypesAndSettings_IndexSizeT : public AbridgedTypesAndSettings {
using Index = size_t;
};
struct TypesAndSettings_Hash32 : public DefaultTypesAndSettings {
struct TypesAndSettings_Hash32 : public AbridgedTypesAndSettings {
using Hash = uint32_t;
static Hash HashFn(const Key& key, Hash raw_seed) {
// This MurmurHash1 function does not pass tests below without the
@ -209,29 +283,29 @@ struct TypesAndSettings_Hash32 : public DefaultTypesAndSettings {
return ROCKSDB_NAMESPACE::Hash(key.data(), key.size(), raw_seed);
}
};
struct TypesAndSettings_Hash32_Result16 : public TypesAndSettings_Hash32 {
struct TypesAndSettings_Hash32_Result16 : public AbridgedTypesAndSettings {
using ResultRow = uint16_t;
};
struct TypesAndSettings_KeyString : public DefaultTypesAndSettings {
struct TypesAndSettings_KeyString : public AbridgedTypesAndSettings {
using Key = std::string;
};
struct TypesAndSettings_Seed8 : public DefaultTypesAndSettings {
struct TypesAndSettings_Seed8 : public AbridgedTypesAndSettings {
// This is not a generally recommended configuration. With the configured
// hash function, it would fail with SmallKeyGen due to insufficient
// independence among the seeds.
using Seed = uint8_t;
};
struct TypesAndSettings_NoAlwaysOne : public DefaultTypesAndSettings {
struct TypesAndSettings_NoAlwaysOne : public AbridgedTypesAndSettings {
static constexpr bool kFirstCoeffAlwaysOne = false;
};
struct TypesAndSettings_AllowZeroStarts : public DefaultTypesAndSettings {
struct TypesAndSettings_AllowZeroStarts : public AbridgedTypesAndSettings {
static constexpr bool kAllowZeroStarts = true;
};
struct TypesAndSettings_Seed64 : public DefaultTypesAndSettings {
struct TypesAndSettings_Seed64 : public AbridgedTypesAndSettings {
using Seed = uint64_t;
};
struct TypesAndSettings_Rehasher
: public StandardRehasherAdapter<DefaultTypesAndSettings> {
: public StandardRehasherAdapter<AbridgedTypesAndSettings> {
using KeyGen = Hash64KeyGenWrapper<StandardKeyGen>;
};
struct TypesAndSettings_Rehasher_Result16 : public TypesAndSettings_Rehasher {
@ -253,7 +327,7 @@ struct TypesAndSettings_Rehasher32_Coeff64
: public TypesAndSettings_Rehasher32 {
using CoeffRow = uint64_t;
};
struct TypesAndSettings_SmallKeyGen : public DefaultTypesAndSettings {
struct TypesAndSettings_SmallKeyGen : public AbridgedTypesAndSettings {
// SmallKeyGen stresses the independence of different hash seeds
using KeyGen = SmallKeyGen;
};
@ -261,11 +335,25 @@ struct TypesAndSettings_Hash32_SmallKeyGen : public TypesAndSettings_Hash32 {
// SmallKeyGen stresses the independence of different hash seeds
using KeyGen = SmallKeyGen;
};
struct TypesAndSettings_Coeff32 : public DefaultTypesAndSettings {
using CoeffRow = uint32_t;
};
struct TypesAndSettings_Coeff32Smash : public TypesAndSettings_Coeff32 {
static constexpr bool kUseSmash = true;
};
struct TypesAndSettings_Coeff16 : public DefaultTypesAndSettings {
using CoeffRow = uint16_t;
};
struct TypesAndSettings_Coeff16Smash : public TypesAndSettings_Coeff16 {
static constexpr bool kUseSmash = true;
};
using TestTypesAndSettings = ::testing::Types<
TypesAndSettings_Coeff128, TypesAndSettings_Coeff128Smash,
TypesAndSettings_Coeff64, TypesAndSettings_Coeff64Smash0,
TypesAndSettings_Coeff64Smash1, TypesAndSettings_Result16,
TypesAndSettings_Coeff64, TypesAndSettings_Coeff64Smash,
TypesAndSettings_Coeff64Smash0, TypesAndSettings_Coeff128_Homog,
TypesAndSettings_Coeff128Smash_Homog, TypesAndSettings_Coeff64_Homog,
TypesAndSettings_Coeff64Smash_Homog, TypesAndSettings_Result16,
TypesAndSettings_Result32, TypesAndSettings_IndexSizeT,
TypesAndSettings_Hash32, TypesAndSettings_Hash32_Result16,
TypesAndSettings_KeyString, TypesAndSettings_Seed8,
@ -274,7 +362,9 @@ using TestTypesAndSettings = ::testing::Types<
TypesAndSettings_Rehasher_Result16, TypesAndSettings_Rehasher_Result32,
TypesAndSettings_Rehasher_Seed64, TypesAndSettings_Rehasher32,
TypesAndSettings_Rehasher32_Coeff64, TypesAndSettings_SmallKeyGen,
TypesAndSettings_Hash32_SmallKeyGen>;
TypesAndSettings_Hash32_SmallKeyGen, TypesAndSettings_Coeff32,
TypesAndSettings_Coeff32Smash, TypesAndSettings_Coeff16,
TypesAndSettings_Coeff16Smash>;
TYPED_TEST_CASE(RibbonTypeParamTest, TestTypesAndSettings);
namespace {
@ -318,22 +408,64 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
IMPORT_RIBBON_TYPES_AND_SETTINGS(TypeParam);
IMPORT_RIBBON_IMPL_TYPES(TypeParam);
using KeyGen = typename TypeParam::KeyGen;
using ConfigHelper =
ROCKSDB_NAMESPACE::ribbon::BandingConfigHelper<TypeParam>;
// For testing FP rate etc.
constexpr Index kNumToCheck = 100000;
if (sizeof(CoeffRow) < 8) {
ROCKSDB_GTEST_SKIP("Not fully supported");
return;
}
const auto log2_thoroughness =
static_cast<Hash>(ROCKSDB_NAMESPACE::FloorLog2(FLAGS_thoroughness));
static_cast<uint32_t>(ROCKSDB_NAMESPACE::FloorLog2(FLAGS_thoroughness));
// With overhead of just 2%, expect ~50% encoding success per
// seed with ~5k keys on 64-bit ribbon, or ~150k keys on 128-bit ribbon.
const double kFactor = 1.02;
// We are going to choose num_to_add using an exponential distribution,
// so that we have good representation of small-to-medium filters.
// Here we just pick some reasonable, practical upper bound based on
// kCoeffBits or option.
const double log_max_add = std::log(
FLAGS_max_add > 0 ? FLAGS_max_add
: static_cast<uint32_t>(kCoeffBits * kCoeffBits) *
std::max(FLAGS_thoroughness, uint32_t{32}));
// This needs to be enough below the minimum number of slots to get a
// reasonable number of samples with the minimum number of slots.
const double log_min_add = std::log(0.66 * SimpleSoln::RoundUpNumSlots(1));
ASSERT_GT(log_max_add, log_min_add);
const double diff_log_add = log_max_add - log_min_add;
for (ConstructionFailureChance cs : TypeParam::FailureChanceToTest()) {
double expected_reseeds;
switch (cs) {
default:
assert(false);
FALLTHROUGH_INTENDED;
case ROCKSDB_NAMESPACE::ribbon::kOneIn2:
fprintf(stderr, "== Failure: 50 percent\n");
expected_reseeds = 1.0;
break;
case ROCKSDB_NAMESPACE::ribbon::kOneIn20:
fprintf(stderr, "== Failure: 95 percent\n");
expected_reseeds = 0.053;
break;
case ROCKSDB_NAMESPACE::ribbon::kOneIn1000:
fprintf(stderr, "== Failure: 1/1000\n");
expected_reseeds = 0.001;
break;
}
uint64_t total_reseeds = 0;
uint64_t total_singles = 0;
uint64_t total_single_failures = 0;
uint64_t total_batch = 0;
uint64_t total_batch_successes = 0;
uint64_t total_fp_count = 0;
uint64_t total_added = 0;
uint64_t total_expand_trials = 0;
uint64_t total_expand_failures = 0;
double total_expand_overhead = 0.0;
uint64_t soln_query_nanos = 0;
uint64_t soln_query_count = 0;
@ -345,26 +477,47 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
ROCKSDB_NAMESPACE::Random32 rnd(FLAGS_thoroughness);
for (uint32_t i = 0; i < FLAGS_thoroughness; ++i) {
uint32_t num_to_add =
sizeof(CoeffRow) == 16 ? 130000 : TypeParam::kUseSmash ? 5500 : 2500;
// Use different values between that number and 50% of that number
num_to_add -= rnd.Uniformish(num_to_add / 2);
total_added += num_to_add;
// We are going to choose num_to_add using an exponential distribution
// as noted above, but instead of randomly choosing them, we generate
// samples linearly using the golden ratio, which ensures a nice spread
// even for a small number of samples, and starting with the minimum
// number of slots to ensure it is tested.
double log_add =
std::fmod(0.6180339887498948482 * diff_log_add * i, diff_log_add) +
log_min_add;
uint32_t num_to_add = static_cast<uint32_t>(std::exp(log_add));
// Most of the time, test the Interleaved solution storage, but when
// we do we have to make num_slots a multiple of kCoeffBits. So
// sometimes we want to test without that limitation.
bool test_interleaved = (i % 7) != 6;
Index num_slots = static_cast<Index>(num_to_add * kFactor);
// Compute num_slots, and re-adjust num_to_add to get as close as possible
// to next num_slots, to stress that num_slots in terms of construction
// success. Ensure at least one iteration:
Index num_slots = Index{0} - 1;
--num_to_add;
for (;;) {
Index next_num_slots = SimpleSoln::RoundUpNumSlots(
ConfigHelper::GetNumSlots(num_to_add + 1, cs));
if (test_interleaved) {
// Round to supported number of slots
num_slots = InterleavedSoln::RoundUpNumSlots(num_slots);
// Re-adjust num_to_add to get as close as possible to kFactor
num_to_add = static_cast<uint32_t>(num_slots / kFactor);
next_num_slots = InterleavedSoln::RoundUpNumSlots(next_num_slots);
// assert idempotent
EXPECT_EQ(next_num_slots,
InterleavedSoln::RoundUpNumSlots(next_num_slots));
}
// assert idempotent with InterleavedSoln::RoundUpNumSlots
EXPECT_EQ(next_num_slots, SimpleSoln::RoundUpNumSlots(next_num_slots));
if (next_num_slots > num_slots) {
break;
}
num_slots = next_num_slots;
++num_to_add;
}
assert(num_slots < Index{0} - 1);
total_added += num_to_add;
std::string prefix;
ROCKSDB_NAMESPACE::PutFixed32(&prefix, rnd.Next());
@ -379,21 +532,32 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
KeyGen two_more(prefix + "more", 2);
// Batch that may or may not be added
const Index kBatchSize =
sizeof(CoeffRow) == 16 ? 300 : TypeParam::kUseSmash ? 20 : 10;
uint32_t batch_size =
static_cast<uint32_t>(2.0 * std::sqrt(num_slots - num_to_add));
if (batch_size < 10U) {
batch_size = 0;
}
std::string batch_str = prefix + "batch";
KeyGen batch_begin(batch_str, 0);
KeyGen batch_end(batch_str, kBatchSize);
KeyGen batch_end(batch_str, batch_size);
// Batch never (successfully) added, but used for querying FP rate
std::string not_str = prefix + "not";
KeyGen other_keys_begin(not_str, 0);
KeyGen other_keys_end(not_str, kNumToCheck);
KeyGen other_keys_end(not_str, FLAGS_max_check);
double overhead_ratio = 1.0 * num_slots / num_to_add;
if (FLAGS_verbose) {
fprintf(stderr, "Adding(%s) %u / %u Overhead: %g Batch size: %u\n",
test_interleaved ? "i" : "s", (unsigned)num_to_add,
(unsigned)num_slots, overhead_ratio, (unsigned)batch_size);
}
// Vary bytes for InterleavedSoln to use number of solution columns
// from 0 to max allowed by ResultRow type (and used by SimpleSoln).
// Specifically include 0 and max, and otherwise skew toward max.
uint32_t max_ibytes = static_cast<uint32_t>(sizeof(ResultRow) * num_slots);
uint32_t max_ibytes =
static_cast<uint32_t>(sizeof(ResultRow) * num_slots);
size_t ibytes;
if (i == 0) {
ibytes = 0;
@ -401,7 +565,8 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
ibytes = max_ibytes;
} else {
// Skewed
ibytes = std::max(rnd.Uniformish(max_ibytes), rnd.Uniformish(max_ibytes));
ibytes =
std::max(rnd.Uniformish(max_ibytes), rnd.Uniformish(max_ibytes));
}
std::unique_ptr<char[]> idata(new char[ibytes]);
InterleavedSoln isoln(idata.get(), ibytes);
@ -417,30 +582,45 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
ASSERT_TRUE(
banding.ResetAndFindSeedToSolve(num_slots, keys_begin, keys_end));
Index occupied_count = banding.GetOccupiedCount();
Index more_added = 0;
if (TypeParam::kHomogeneous || overhead_ratio < 1.01 ||
batch_size == 0) {
// Homogeneous not compatible with backtracking because add
// doesn't fail. Small overhead ratio too packed to expect more
first_single = false;
second_single = false;
batch_success = false;
} else {
// Now to test backtracking, starting with guaranteed fail. By using
// the keys that will be used to test FP rate, we are then doing an
// extra check that after backtracking there are no remnants (e.g. in
// result side of banding) of these entries.
Index occupied_count = banding.GetOccupiedCount();
banding.EnsureBacktrackSize(kNumToCheck);
EXPECT_FALSE(
banding.AddRangeOrRollBack(other_keys_begin, other_keys_end));
KeyGen other_keys_too_big_end = other_keys_begin;
other_keys_too_big_end += num_to_add;
banding.EnsureBacktrackSize(std::max(num_to_add, batch_size));
EXPECT_FALSE(banding.AddRangeOrRollBack(other_keys_begin,
other_keys_too_big_end));
EXPECT_EQ(occupied_count, banding.GetOccupiedCount());
// Check that we still have a good chance of adding a couple more
// individually
first_single = banding.Add(*one_more);
second_single = banding.Add(*two_more);
Index more_added = (first_single ? 1 : 0) + (second_single ? 1 : 0);
more_added += (first_single ? 1 : 0) + (second_single ? 1 : 0);
total_singles += 2U;
total_single_failures += 2U - more_added;
// Or as a batch
batch_success = banding.AddRangeOrRollBack(batch_begin, batch_end);
++total_batch;
if (batch_success) {
more_added += kBatchSize;
more_added += batch_size;
++total_batch_successes;
}
EXPECT_LE(banding.GetOccupiedCount(), occupied_count + more_added);
}
// Also verify that redundant adds are OK (no effect)
ASSERT_TRUE(
@ -464,6 +644,32 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
static_cast<unsigned>(i), static_cast<unsigned>(num_to_add),
static_cast<unsigned>(num_slots), static_cast<unsigned>(reseeds));
}
if (reseeds > 0) {
// "Expand" test: given a failed construction, how likely is it to
// pass with same seed and more slots. At each step, we increase
// enough to ensure there is at least one shift within each coeff
// block.
++total_expand_trials;
Index expand_count = 0;
Index ex_slots = num_slots;
banding.SetOrdinalSeed(0);
for (;; ++expand_count) {
ASSERT_LE(expand_count, log2_thoroughness);
ex_slots += ex_slots / kCoeffBits;
if (test_interleaved) {
ex_slots = InterleavedSoln::RoundUpNumSlots(ex_slots);
}
banding.Reset(ex_slots);
bool success = banding.AddRange(keys_begin, keys_end);
if (success) {
break;
}
}
total_expand_failures += expand_count;
total_expand_overhead += 1.0 * (ex_slots - num_slots) / num_slots;
}
hasher.SetOrdinalSeed(reseeds);
}
// soln and hasher now independent of Banding object
@ -493,7 +699,8 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
}
}
// Check FP rate (depends only on number of result bits == solution columns)
// Check FP rate (depends only on number of result bits == solution
// columns)
Index fp_count = 0;
cur = other_keys_begin;
{
@ -505,14 +712,16 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
++cur;
}
soln_query_nanos += timer.ElapsedNanos();
soln_query_count += kNumToCheck;
soln_query_count += FLAGS_max_check;
}
{
double expected_fp_count = soln.ExpectedFpRate() * kNumToCheck;
double expected_fp_count = soln.ExpectedFpRate() * FLAGS_max_check;
// For expected FP rate, also include false positives due to collisions
// in Hash value. (Negligible for 64-bit, can matter for 32-bit.)
double correction =
kNumToCheck * ExpectedCollisionFpRate(hasher, num_to_add);
FLAGS_max_check * ExpectedCollisionFpRate(hasher, num_to_add);
// NOTE: rare violations expected with kHomogeneous
EXPECT_LE(fp_count,
FrequentPoissonUpperBound(expected_fp_count + correction));
EXPECT_GE(fp_count,
@ -531,17 +740,23 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
++cur;
}
isoln_query_nanos += timer.ElapsedNanos();
isoln_query_count += kNumToCheck;
isoln_query_count += FLAGS_max_check;
{
double expected_fp_count = isoln.ExpectedFpRate() * kNumToCheck;
// For expected FP rate, also include false positives due to collisions
// in Hash value. (Negligible for 64-bit, can matter for 32-bit.)
double expected_fp_count = isoln.ExpectedFpRate() * FLAGS_max_check;
// For expected FP rate, also include false positives due to
// collisions in Hash value. (Negligible for 64-bit, can matter for
// 32-bit.)
double correction =
kNumToCheck * ExpectedCollisionFpRate(hasher, num_to_add);
FLAGS_max_check * ExpectedCollisionFpRate(hasher, num_to_add);
// NOTE: rare violations expected with kHomogeneous
EXPECT_LE(ifp_count,
FrequentPoissonUpperBound(expected_fp_count + correction));
EXPECT_GE(ifp_count,
FrequentPoissonLowerBound(expected_fp_count + correction));
// FIXME: why sometimes can we slightly "beat the odds"?
// (0.95 factor should not be needed)
EXPECT_GE(ifp_count, FrequentPoissonLowerBound(
0.95 * expected_fp_count + correction));
}
// Since the bits used in isoln are a subset of the bits used in soln,
// it cannot have fewer FPs
@ -559,7 +774,8 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
uint32_t h1 = ROCKSDB_NAMESPACE::Lower32of64(h);
uint32_t h2 = sizeof(Hash) >= 8 ? ROCKSDB_NAMESPACE::Upper32of64(h)
: h1 * 0x9e3779b9;
bfp_count += ROCKSDB_NAMESPACE::FastLocalBloomImpl::HashMayMatch(
bfp_count +=
ROCKSDB_NAMESPACE::FastLocalBloomImpl::HashMayMatch(
h1, h2, static_cast<uint32_t>(ibytes), 6, idata.get())
? 1
: 0;
@ -567,37 +783,56 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
}
bloom_query_nanos += timer.ElapsedNanos();
// ensure bfp_count is used
ASSERT_LT(bfp_count, kNumToCheck);
ASSERT_LT(bfp_count, FLAGS_max_check);
}
}
// "outside" == key not in original set so either negative or false positive
fprintf(stderr, "Simple outside query, hot, incl hashing, ns/key: %g\n",
fprintf(stderr,
"Simple outside query, hot, incl hashing, ns/key: %g\n",
1.0 * soln_query_nanos / soln_query_count);
fprintf(stderr, "Interleaved outside query, hot, incl hashing, ns/key: %g\n",
fprintf(stderr,
"Interleaved outside query, hot, incl hashing, ns/key: %g\n",
1.0 * isoln_query_nanos / isoln_query_count);
fprintf(stderr, "Bloom outside query, hot, incl hashing, ns/key: %g\n",
fprintf(stderr,
"Bloom outside query, hot, incl hashing, ns/key: %g\n",
1.0 * bloom_query_nanos / soln_query_count);
{
if (TypeParam::kHomogeneous) {
EXPECT_EQ(total_reseeds, 0U);
} else {
double average_reseeds = 1.0 * total_reseeds / FLAGS_thoroughness;
fprintf(stderr, "Average re-seeds: %g\n", average_reseeds);
// Values above were chosen to target around 50% chance of encoding success
// rate (average of 1.0 re-seeds) or slightly better. But 1.15 is also close
// enough.
// Values above were chosen to target around 50% chance of encoding
// success rate (average of 1.0 re-seeds) or slightly better. But 1.15 is
// also close enough.
EXPECT_LE(total_reseeds,
InfrequentPoissonUpperBound(1.15 * FLAGS_thoroughness));
InfrequentPoissonUpperBound(1.15 * expected_reseeds *
FLAGS_thoroughness));
// Would use 0.85 here instead of 0.75, but
// TypesAndSettings_Hash32_SmallKeyGen can "beat the odds" because of
// sequential keys with a small, cheap hash function. We accept that
// there are surely inputs that are somewhat bad for this setup, but
// these somewhat good inputs are probably more likely.
EXPECT_GE(total_reseeds,
InfrequentPoissonLowerBound(0.75 * FLAGS_thoroughness));
InfrequentPoissonLowerBound(0.75 * expected_reseeds *
FLAGS_thoroughness));
}
{
uint64_t total_singles = 2 * FLAGS_thoroughness;
if (total_expand_trials > 0) {
double average_expand_failures =
1.0 * total_expand_failures / total_expand_trials;
fprintf(stderr, "Average expand failures, and overhead: %g, %g\n",
average_expand_failures,
total_expand_overhead / total_expand_trials);
// Seems to be a generous allowance
EXPECT_LE(total_expand_failures,
InfrequentPoissonUpperBound(1.0 * total_expand_trials));
} else {
fprintf(stderr, "Average expand failures: N/A\n");
}
if (total_singles > 0) {
double single_failure_rate = 1.0 * total_single_failures / total_singles;
fprintf(stderr, "Add'l single, failure rate: %g\n", single_failure_rate);
// A rough bound (one sided) based on nothing in particular
@ -608,21 +843,21 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
InfrequentPoissonUpperBound(expected_single_failures));
}
{
if (total_batch > 0) {
// Counting successes here for Poisson to approximate the Binomial
// distribution.
// A rough bound (one sided) based on nothing in particular.
double expected_batch_successes = 1.0 * FLAGS_thoroughness / 2;
double expected_batch_successes = 1.0 * total_batch / 2;
uint64_t lower_bound =
InfrequentPoissonLowerBound(expected_batch_successes);
fprintf(stderr, "Add'l batch, success rate: %g (>= %g)\n",
1.0 * total_batch_successes / FLAGS_thoroughness,
1.0 * lower_bound / FLAGS_thoroughness);
1.0 * total_batch_successes / total_batch,
1.0 * lower_bound / total_batch);
EXPECT_GE(total_batch_successes, lower_bound);
}
{
uint64_t total_checked = uint64_t{kNumToCheck} * FLAGS_thoroughness;
uint64_t total_checked = uint64_t{FLAGS_max_check} * FLAGS_thoroughness;
double expected_total_fp_count =
total_checked * std::pow(0.5, 8U * sizeof(ResultRow));
// For expected FP rate, also include false positives due to collisions
@ -631,8 +866,10 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
expected_total_fp_count +=
total_checked * ExpectedCollisionFpRate(Hasher(), average_added);
uint64_t upper_bound = InfrequentPoissonUpperBound(expected_total_fp_count);
uint64_t lower_bound = InfrequentPoissonLowerBound(expected_total_fp_count);
uint64_t upper_bound =
InfrequentPoissonUpperBound(expected_total_fp_count);
uint64_t lower_bound =
InfrequentPoissonLowerBound(expected_total_fp_count);
fprintf(stderr, "Average FP rate: %g (~= %g, <= %g, >= %g)\n",
1.0 * total_fp_count / total_checked,
expected_total_fp_count / total_checked,
@ -641,6 +878,7 @@ TYPED_TEST(RibbonTypeParamTest, CompactnessAndBacktrackAndFpRate) {
EXPECT_LE(total_fp_count, upper_bound);
EXPECT_GE(total_fp_count, lower_bound);
}
}
}
TYPED_TEST(RibbonTypeParamTest, Extremes) {
@ -672,9 +910,8 @@ TYPED_TEST(RibbonTypeParamTest, Extremes) {
// Somewhat oddly, we expect same FP rate as if we had essentially filled
// up the slots.
constexpr Index kNumToCheck = 100000;
KeyGen other_keys_begin("not", 0);
KeyGen other_keys_end("not", kNumToCheck);
KeyGen other_keys_end("not", FLAGS_max_check);
Index fp_count = 0;
KeyGen cur = other_keys_begin;
@ -683,20 +920,26 @@ TYPED_TEST(RibbonTypeParamTest, Extremes) {
bool soln_query_result = soln.FilterQuery(*cur, hasher);
// Solutions are equivalent
ASSERT_EQ(isoln_query_result, soln_query_result);
if (!TypeParam::kHomogeneous) {
// And in fact we only expect an FP when ResultRow is 0
// CHANGE: no longer true because of filling some unused slots
// with pseudorandom values.
// ASSERT_EQ(soln_query_result, hasher.GetResultRowFromHash(
// hasher.GetHash(*cur)) == ResultRow{0});
// (except Homogeneous)
ASSERT_EQ(soln_query_result, hasher.GetResultRowFromHash(
hasher.GetHash(*cur)) == ResultRow{0});
}
fp_count += soln_query_result ? 1 : 0;
++cur;
}
{
ASSERT_EQ(isoln.ExpectedFpRate(), soln.ExpectedFpRate());
double expected_fp_count = isoln.ExpectedFpRate() * kNumToCheck;
double expected_fp_count = isoln.ExpectedFpRate() * FLAGS_max_check;
EXPECT_LE(fp_count, InfrequentPoissonUpperBound(expected_fp_count));
if (TypeParam::kHomogeneous) {
// Pseudorandom garbage in Homogeneous filter can "beat the odds" if
// nothing added
} else {
EXPECT_GE(fp_count, InfrequentPoissonLowerBound(expected_fp_count));
}
}
// ######################################################
// Use zero bytes for interleaved solution (key(s) added)
@ -874,8 +1117,8 @@ TEST(RibbonTest, PhsfBasic) {
}
}
// Not a real test, but a tool used to build GetNumSlotsFor95PctSuccess
TYPED_TEST(RibbonTypeParamTest, FindOccupancyForSuccessRate) {
// Not a real test, but a tool used to build APIs in ribbon_config.h
TYPED_TEST(RibbonTypeParamTest, FindOccupancy) {
IMPORT_RIBBON_TYPES_AND_SETTINGS(TypeParam);
IMPORT_RIBBON_IMPL_TYPES(TypeParam);
using KeyGen = typename TypeParam::KeyGen;
@ -885,34 +1128,101 @@ TYPED_TEST(RibbonTypeParamTest, FindOccupancyForSuccessRate) {
return;
}
KeyGen cur("blah", 0);
KeyGen cur(ROCKSDB_NAMESPACE::ToString(
testing::UnitTest::GetInstance()->random_seed()),
0);
Banding banding;
Index num_slots = InterleavedSoln::RoundUpNumSlots(FLAGS_find_min_slots);
while (num_slots < FLAGS_find_max_slots) {
double factor = 0.95;
double delta = FLAGS_find_delta_start;
while (delta > FLAGS_find_delta_end) {
Index num_to_add = static_cast<Index>(factor * num_slots);
Index max_slots = InterleavedSoln::RoundUpNumSlots(FLAGS_find_max_slots);
while (num_slots <= max_slots) {
std::map<int32_t, uint32_t> rem_histogram;
std::map<Index, uint32_t> slot_histogram;
if (FLAGS_find_slot_occ) {
for (Index i = 0; i < kCoeffBits; ++i) {
slot_histogram[i] = 0;
slot_histogram[num_slots - 1 - i] = 0;
slot_histogram[num_slots / 2 - kCoeffBits / 2 + i] = 0;
}
}
uint64_t total_added = 0;
for (uint32_t i = 0; i < FLAGS_find_iters; ++i) {
banding.Reset(num_slots);
uint32_t j = 0;
KeyGen end = cur;
end += num_to_add;
bool success = banding.ResetAndFindSeedToSolve(num_slots, cur, end, 0, 0);
cur = end; // fresh keys
if (success) {
factor += delta * (1.0 - FLAGS_find_success);
factor = std::min(factor, 1.0);
end += num_slots + num_slots / 10;
for (; cur != end; ++cur) {
if (banding.Add(*cur)) {
++j;
} else {
factor -= delta * FLAGS_find_success;
factor = std::max(factor, 0.0);
break;
}
delta *= FLAGS_find_delta_shrink;
fprintf(stderr,
"slots: %u log2_slots: %g target_success: %g ->overhead: %g\r",
static_cast<unsigned>(num_slots),
std::log(num_slots * 1.0) / std::log(2.0), FLAGS_find_success,
1.0 / factor);
}
total_added += j;
for (auto& slot : slot_histogram) {
slot.second += banding.IsOccupied(slot.first);
}
int32_t bucket =
static_cast<int32_t>(num_slots) - static_cast<int32_t>(j);
rem_histogram[bucket]++;
if (FLAGS_verbose) {
fprintf(stderr, "num_slots: %u i: %u / %u avg_overhead: %g\r",
static_cast<unsigned>(num_slots), static_cast<unsigned>(i),
static_cast<unsigned>(FLAGS_find_iters),
1.0 * (i + 1) * num_slots / total_added);
}
}
if (FLAGS_verbose) {
fprintf(stderr, "\n");
}
uint32_t cumulative = 0;
double p50_rem = 0;
double p95_rem = 0;
double p99_9_rem = 0;
for (auto& h : rem_histogram) {
double before = 1.0 * cumulative / FLAGS_find_iters;
double not_after = 1.0 * (cumulative + h.second) / FLAGS_find_iters;
if (FLAGS_verbose) {
fprintf(stderr, "overhead: %g before: %g not_after: %g\n",
1.0 * num_slots / (num_slots - h.first), before, not_after);
}
cumulative += h.second;
if (before < 0.5 && 0.5 <= not_after) {
// fake it with linear interpolation
double portion = (0.5 - before) / (not_after - before);
p50_rem = h.first + portion;
} else if (before < 0.95 && 0.95 <= not_after) {
// fake it with linear interpolation
double portion = (0.95 - before) / (not_after - before);
p95_rem = h.first + portion;
} else if (before < 0.999 && 0.999 <= not_after) {
// fake it with linear interpolation
double portion = (0.999 - before) / (not_after - before);
p99_9_rem = h.first + portion;
}
}
for (auto& slot : slot_histogram) {
fprintf(stderr, "slot[%u] occupied: %g\n", (unsigned)slot.first,
1.0 * slot.second / FLAGS_find_iters);
}
double mean_rem =
(1.0 * FLAGS_find_iters * num_slots - total_added) / FLAGS_find_iters;
fprintf(
stderr,
"num_slots: %u iters: %u mean_ovr: %g p50_ovr: %g p95_ovr: %g "
"p99.9_ovr: %g mean_rem: %g p50_rem: %g p95_rem: %g p99.9_rem: %g\n",
static_cast<unsigned>(num_slots),
static_cast<unsigned>(FLAGS_find_iters),
1.0 * num_slots / (num_slots - mean_rem),
1.0 * num_slots / (num_slots - p50_rem),
1.0 * num_slots / (num_slots - p95_rem),
1.0 * num_slots / (num_slots - p99_9_rem), mean_rem, p50_rem, p95_rem,
p99_9_rem);
num_slots = std::max(
num_slots + 1, static_cast<Index>(num_slots * FLAGS_find_next_factor));
@ -920,8 +1230,74 @@ TYPED_TEST(RibbonTypeParamTest, FindOccupancyForSuccessRate) {
}
}
// TODO: unit tests for configuration APIs
// TODO: unit tests for small filter FP rates
// Not a real test, but a tool to understand Homogeneous Ribbon
// behavior (TODO: configuration APIs & tests)
TYPED_TEST(RibbonTypeParamTest, OptimizeHomogAtScale) {
IMPORT_RIBBON_TYPES_AND_SETTINGS(TypeParam);
IMPORT_RIBBON_IMPL_TYPES(TypeParam);
using KeyGen = typename TypeParam::KeyGen;
if (!FLAGS_optimize_homog) {
fprintf(stderr, "Tool disabled during unit test runs\n");
return;
}
if (!TypeParam::kHomogeneous) {
fprintf(stderr, "Only for Homogeneous Ribbon\n");
return;
}
KeyGen cur(ROCKSDB_NAMESPACE::ToString(
testing::UnitTest::GetInstance()->random_seed()),
0);
Banding banding;
Index num_slots = SimpleSoln::RoundUpNumSlots(FLAGS_optimize_homog_slots);
banding.Reset(num_slots);
// This and "band_ovr" is the "allocated overhead", or slots over added.
// It does not take into account FP rates.
double target_overhead = 1.20;
uint32_t num_added = 0;
do {
do {
(void)banding.Add(*cur);
++cur;
++num_added;
} while (1.0 * num_slots / num_added > target_overhead);
SimpleSoln soln;
soln.BackSubstFrom(banding);
std::array<uint32_t, 8U * sizeof(ResultRow)> fp_counts_by_cols;
fp_counts_by_cols.fill(0U);
for (uint32_t i = 0; i < FLAGS_optimize_homog_check; ++i) {
ResultRow r = soln.PhsfQuery(*cur, banding);
++cur;
for (size_t j = 0; j < fp_counts_by_cols.size(); ++j) {
if ((r & 1) == 1) {
break;
}
fp_counts_by_cols[j]++;
r /= 2;
}
}
fprintf(stderr, "band_ovr: %g ", 1.0 * num_slots / num_added);
for (unsigned j = 0; j < fp_counts_by_cols.size(); ++j) {
double inv_fp_rate =
1.0 * FLAGS_optimize_homog_check / fp_counts_by_cols[j];
double equiv_cols = std::log(inv_fp_rate) * 1.4426950409;
// Overhead vs. information-theoretic minimum based on observed
// FP rate (subject to sampling error, especially for low FP rates)
double actual_overhead =
1.0 * (j + 1) * num_slots / (equiv_cols * num_added);
fprintf(stderr, "ovr_%u: %g ", j + 1, actual_overhead);
}
fprintf(stderr, "\n");
target_overhead -= FLAGS_optimize_homog_granularity;
} while (target_overhead > 1.0);
}
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);