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Core sketch algorithms used alone and by other Java repositories in the DataSketches library.
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.datasketches.thetacommon;
import static org.apache.datasketches.common.Util.LONG_MAX_VALUE_AS_DOUBLE;
import org.apache.datasketches.common.BoundsOnRatiosInSampledSets;
import org.apache.datasketches.common.SketchesArgumentException;
import org.apache.datasketches.tuple.Sketch;
import org.apache.datasketches.tuple.Summary;
/**
* This class is used to compute the bounds on the estimate of the ratio B / A, where:
*
* - A is a Tuple Sketch of population PopA.
* - B is a Tuple or Theta Sketch of population PopB that is a subset of A,
* obtained by an intersection of A with some other Tuple or Theta Sketch C,
* which acts like a predicate or selection clause.
* - The estimate of the ratio PopB/PopA is
* BoundsOnRatiosInThetaSketchedSets.getEstimateOfBoverA(A, B).
* - The Upper Bound estimate on the ratio PopB/PopA is
* BoundsOnRatiosInThetaSketchedSets.getUpperBoundForBoverA(A, B).
* - The Lower Bound estimate on the ratio PopB/PopA is
* BoundsOnRatiosInThetaSketchedSets.getLowerBoundForBoverA(A, B).
*
* Note: The theta of A cannot be greater than the theta of B.
* If B is formed as an intersection of A and some other set C,
* then the theta of B is guaranteed to be less than or equal to the theta of B.
*
* @author Kevin Lang
* @author Lee Rhodes
* @author David Cromberge
*/
public final class BoundsOnRatiosInTupleSketchedSets {
private BoundsOnRatiosInTupleSketchedSets() {}
/**
* Gets the approximate lower bound for B over A based on a 95% confidence interval
* @param sketchA the Tuple sketch A with summary type S
* @param sketchB the Tuple sketch B with summary type S
* @param Summary
* @return the approximate lower bound for B over A
*/
public static double getLowerBoundForBoverA(
final Sketch sketchA,
final Sketch sketchB) {
final long thetaLongA = sketchA.getThetaLong();
final long thetaLongB = sketchB.getThetaLong();
checkThetas(thetaLongA, thetaLongB);
final int countB = sketchB.getRetainedEntries();
final int countA = thetaLongB == thetaLongA
? sketchA.getRetainedEntries()
: sketchA.getCountLessThanThetaLong(thetaLongB);
if (countA <= 0) { return 0; }
final double f = thetaLongB / LONG_MAX_VALUE_AS_DOUBLE;
return BoundsOnRatiosInSampledSets.getLowerBoundForBoverA(countA, countB, f);
}
/**
* Gets the approximate lower bound for B over A based on a 95% confidence interval
* @param sketchA the Tuple sketch A with summary type S
* @param sketchB the Theta sketch B
* @param Summary
* @return the approximate lower bound for B over A
*/
public static double getLowerBoundForBoverA(
final Sketch sketchA,
final org.apache.datasketches.theta.Sketch sketchB) {
final long thetaLongA = sketchA.getThetaLong();
final long thetaLongB = sketchB.getThetaLong();
checkThetas(thetaLongA, thetaLongB);
final int countB = sketchB.getRetainedEntries();
final int countA = thetaLongB == thetaLongA
? sketchA.getRetainedEntries()
: sketchA.getCountLessThanThetaLong(thetaLongB);
if (countA <= 0) { return 0; }
final double f = thetaLongB / LONG_MAX_VALUE_AS_DOUBLE;
return BoundsOnRatiosInSampledSets.getLowerBoundForBoverA(countA, countB, f);
}
/**
* Gets the approximate upper bound for B over A based on a 95% confidence interval
* @param sketchA the Tuple sketch A with summary type S
* @param sketchB the Tuple sketch B with summary type S
* @param Summary
* @return the approximate upper bound for B over A
*/
public static double getUpperBoundForBoverA(
final Sketch sketchA,
final Sketch sketchB) {
final long thetaLongA = sketchA.getThetaLong();
final long thetaLongB = sketchB.getThetaLong();
checkThetas(thetaLongA, thetaLongB);
final int countB = sketchB.getRetainedEntries();
final int countA = thetaLongB == thetaLongA
? sketchA.getRetainedEntries()
: sketchA.getCountLessThanThetaLong(thetaLongB);
if (countA <= 0) { return 1.0; }
final double f = thetaLongB / LONG_MAX_VALUE_AS_DOUBLE;
return BoundsOnRatiosInSampledSets.getUpperBoundForBoverA(countA, countB, f);
}
/**
* Gets the approximate upper bound for B over A based on a 95% confidence interval
* @param sketchA the Tuple sketch A with summary type S
* @param sketchB the Theta sketch B
* @param Summary
* @return the approximate upper bound for B over A
*/
public static double getUpperBoundForBoverA(
final Sketch sketchA,
final org.apache.datasketches.theta.Sketch sketchB) {
final long thetaLongA = sketchA.getThetaLong();
final long thetaLongB = sketchB.getThetaLong();
checkThetas(thetaLongA, thetaLongB);
final int countB = sketchB.getRetainedEntries(true);
final int countA = thetaLongB == thetaLongA
? sketchA.getRetainedEntries()
: sketchA.getCountLessThanThetaLong(thetaLongB);
if (countA <= 0) { return 1.0; }
final double f = thetaLongB / LONG_MAX_VALUE_AS_DOUBLE;
return BoundsOnRatiosInSampledSets.getUpperBoundForBoverA(countA, countB, f);
}
/**
* Gets the estimate for B over A
* @param sketchA the Tuple sketch A with summary type S
* @param sketchB the Tuple sketch B with summary type S
* @param Summary
* @return the estimate for B over A
*/
public static double getEstimateOfBoverA(
final Sketch sketchA,
final Sketch sketchB) {
final long thetaLongA = sketchA.getThetaLong();
final long thetaLongB = sketchB.getThetaLong();
checkThetas(thetaLongA, thetaLongB);
final int countB = sketchB.getRetainedEntries();
final int countA = thetaLongB == thetaLongA
? sketchA.getRetainedEntries()
: sketchA.getCountLessThanThetaLong(thetaLongB);
if (countA <= 0) { return 0.5; }
return (double) countB / (double) countA;
}
/**
* Gets the estimate for B over A
* @param sketchA the Tuple sketch A with summary type S
* @param sketchB the Theta sketch B
* @param Summary
* @return the estimate for B over A
*/
public static double getEstimateOfBoverA(
final Sketch sketchA,
final org.apache.datasketches.theta.Sketch sketchB) {
final long thetaLongA = sketchA.getThetaLong();
final long thetaLongB = sketchB.getThetaLong();
checkThetas(thetaLongA, thetaLongB);
final int countB = sketchB.getRetainedEntries(true);
final int countA = thetaLongB == thetaLongA
? sketchA.getRetainedEntries()
: sketchA.getCountLessThanThetaLong(thetaLongB);
if (countA <= 0) { return 0.5; }
return (double) countB / (double) countA;
}
static void checkThetas(final long thetaLongA, final long thetaLongB) {
if (thetaLongB > thetaLongA) {
throw new SketchesArgumentException("ThetaLongB cannot be > ThetaLongA.");
}
}
}
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