rocksdb/util/histogram.h

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include "rocksdb/statistics.h"
#include <cassert>
#include <string>
#include <vector>
#include <map>
#include <string.h>
namespace rocksdb {
class HistogramBucketMapper {
public:
HistogramBucketMapper();
// converts a value to the bucket index.
size_t IndexForValue(const uint64_t value) const;
// number of buckets required.
size_t BucketCount() const {
return bucketValues_.size();
}
uint64_t LastValue() const {
return maxBucketValue_;
}
uint64_t FirstValue() const {
return minBucketValue_;
}
uint64_t BucketLimit(const size_t bucketNumber) const {
assert(bucketNumber < BucketCount());
return bucketValues_[bucketNumber];
}
private:
const std::vector<uint64_t> bucketValues_;
const uint64_t maxBucketValue_;
const uint64_t minBucketValue_;
std::map<uint64_t, uint64_t> valueIndexMap_;
};
class HistogramImpl {
public:
HistogramImpl() { memset(buckets_, 0, sizeof(buckets_)); }
virtual void Clear();
virtual bool Empty();
virtual void Add(uint64_t value);
void Merge(const HistogramImpl& other);
virtual std::string ToString() const;
virtual double Median() const;
virtual double Percentile(double p) const;
virtual double Average() const;
virtual double StandardDeviation() const;
virtual void Data(HistogramData * const data) const;
virtual ~HistogramImpl() {}
private:
// To be able to use HistogramImpl as thread local variable, its constructor
// has to be static. That's why we're using manually values from BucketMapper
double min_ = 1000000000; // this is BucketMapper:LastValue()
double max_ = 0;
double num_ = 0;
double sum_ = 0;
double sum_squares_ = 0;
uint64_t buckets_[138]; // this is BucketMapper::BucketCount()
};
} // namespace rocksdb