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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.search.aggregations.metrics;
/**
* Base class for cardinality related algorithms.
*/
abstract class AbstractCardinalityAlgorithm {
public static final int MIN_PRECISION = 4;
public static final int MAX_PRECISION = 18;
protected final int p;
AbstractCardinalityAlgorithm(int precision) {
if (precision < MIN_PRECISION) {
throw new IllegalArgumentException("precision must be >= 4");
}
if (precision > MAX_PRECISION) {
throw new IllegalArgumentException("precision must be <= 18");
}
p = precision;
}
/** Precision of the algorithm */
public int precision() {
return p;
}
/** Returns the current computed cardinality */
public abstract long cardinality(long bucketOrd);
static long linearCounting(long m, long v) {
return Math.round(m * Math.log((double) m / v));
}
}