114 lines
2.9 KiB
Java
114 lines
2.9 KiB
Java
package it.cavallium.dbengine.lucene;
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import it.cavallium.dbengine.utils.LFSR.LFSRIterator;
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import java.io.IOException;
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import java.math.BigInteger;
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import org.apache.lucene.index.LeafReaderContext;
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import org.apache.lucene.search.FieldComparator;
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import org.apache.lucene.search.LeafFieldComparator;
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import org.apache.lucene.search.Scorable;
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import org.apache.lucene.search.ScoreCachingWrappingScorer;
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import org.jetbrains.annotations.NotNull;
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//todo: fix
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public class RandomFieldComparator extends FieldComparator<Float> implements LeafFieldComparator {
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private final @NotNull LFSRIterator rand;
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private final float[] scores;
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private float bottom;
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private Scorable scorer;
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private float topValue;
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/** Creates a new comparator based on relevance for {@code numHits}. */
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public RandomFieldComparator(@NotNull LFSRIterator rand, int numHits) {
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this.rand = rand;
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scores = new float[numHits];
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}
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@Override
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public int compare(int slot1, int slot2) {
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return Float.compare(scores[slot2], scores[slot1]);
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}
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@Override
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public int compareBottom(int doc) throws IOException {
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float score = scorer.score();
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assert !Float.isNaN(score);
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return Float.compare(score, bottom);
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}
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@Override
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public void copy(int slot, int doc) throws IOException {
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scores[slot] = scorer.score();
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assert !Float.isNaN(scores[slot]);
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}
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@Override
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public LeafFieldComparator getLeafComparator(LeafReaderContext context) {
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return this;
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}
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@Override
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public void setBottom(final int bottom) {
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this.bottom = scores[bottom];
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}
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@Override
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public void setTopValue(Float value) {
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topValue = Float.MAX_VALUE;
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}
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@Override
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public void setScorer(Scorable scorer) {
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// wrap with a ScoreCachingWrappingScorer so that successive calls to
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// score() will not incur score computation over and
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// over again.
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var randomizedScorer = new Scorable() {
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@Override
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public float score() {
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return randomize(scorer.docID());
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}
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@Override
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public int docID() {
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return scorer.docID();
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}
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};
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this.scorer = ScoreCachingWrappingScorer.wrap(randomizedScorer);
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}
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@SuppressWarnings("RedundantCast")
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@Override
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public Float value(int slot) {
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return (float) scores[slot];
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}
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// Override because we sort reverse of natural Float order:
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@Override
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public int compareValues(Float first, Float second) {
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// Reversed intentionally because relevance by default
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// sorts descending:
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return second.compareTo(first);
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}
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@Override
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public int compareTop(int doc) throws IOException {
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float docValue = scorer.score();
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assert !Float.isNaN(docValue);
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return Float.compare(docValue, topValue);
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}
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private float randomize(int num) {
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int val = rand.next(BigInteger.valueOf(num)).intValueExact();
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int pow24 = 1 << 24;
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if (val >= pow24) {
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throw new IndexOutOfBoundsException();
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}
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if (val < 0) {
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throw new IndexOutOfBoundsException();
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}
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return (val & 0x00FFFFFF) / (float)(1 << 24); // only use the lower 24 bits to construct a float from 0.0-1.0
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}
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}
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