SumOfLogs.java
/*
* 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.commons.statistics.descriptive;
/**
* Returns the sum of the {@link Math#log(double) natural logarithm} of available values.
*
* <ul>
* <li>The result is zero if no values are added.
* <li>The result is {@code NaN} if any of the values is {@code NaN}.
* <li>The result is {@code NaN} if any of the values is negative.
* </ul>
*
* <p>The sum follows the IEEE754 result for summing infinite values:
*
* <ul>
* <li>The result is {@code +infinity} if all values are in the range {@code (0, +infinity]}
* and at least one value is {@code +infinity}.
* <li>The result is {@code -infinity} if all values are in the range {@code [0, +infinity)}
* and at least one value is zero.
* <li>The result is {@code NaN} if all values are in the range {@code [0, +infinity]}
* and at least one value is zero, and one value is {@code +infinity}.
* </ul>
*
* <p>This class is designed to work with (though does not require)
* {@linkplain java.util.stream streams}.
*
* <p><strong>This instance is not thread safe.</strong>
* If multiple threads access an instance of this class concurrently,
* and at least one of the threads invokes the {@link java.util.function.DoubleConsumer#accept(double) accept} or
* {@link StatisticAccumulator#combine(StatisticResult) combine} method, it must be synchronized externally.
*
* <p>However, it is safe to use {@link java.util.function.DoubleConsumer#accept(double) accept}
* and {@link StatisticAccumulator#combine(StatisticResult) combine}
* as {@code accumulator} and {@code combiner} functions of
* {@link java.util.stream.Collector Collector} on a parallel stream,
* because the parallel instance of {@link java.util.stream.Stream#collect Stream.collect()}
* provides the necessary partitioning, isolation, and merging of results for
* safe and efficient parallel execution.
*
* @see org.apache.commons.numbers.core.Sum
* @see Math#log(double)
* @since 1.1
*/
public final class SumOfLogs implements DoubleStatistic, StatisticAccumulator<SumOfLogs> {
/** {@link org.apache.commons.numbers.core.Sum Sum} used to compute the sum. */
private final org.apache.commons.numbers.core.Sum delegate =
org.apache.commons.numbers.core.Sum.create();
/**
* Create an instance.
*/
private SumOfLogs() {
// No-op
}
/**
* Creates an instance.
*
* <p>The initial result is zero.
*
* @return {@code SumOfLogs} instance.
*/
public static SumOfLogs create() {
return new SumOfLogs();
}
/**
* Returns an instance populated using the input {@code values}.
*
* <p>The result is {@code NaN} if any of the values is {@code NaN}
* or negative; or the sum at any point is a {@code NaN}.
*
* <p>When the input is an empty array, the result is zero.
*
* @param values Values.
* @return {@code SumOfLogs} instance.
*/
public static SumOfLogs of(double... values) {
return Statistics.add(new SumOfLogs(), values);
}
/**
* Returns an instance populated using the specified range of {@code values}.
*
* <p>The result is {@code NaN} if any of the values is {@code NaN}
* or negative; or the sum at any point is a {@code NaN}.
*
* <p>When the range is empty, the result is zero.
*
* @param values Values.
* @param from Inclusive start of the range.
* @param to Exclusive end of the range.
* @return {@code SumOfLogs} instance.
* @throws IndexOutOfBoundsException if the sub-range is out of bounds
* @since 1.2
*/
public static SumOfLogs ofRange(double[] values, int from, int to) {
Statistics.checkFromToIndex(from, to, values.length);
return createFromRange(values, from, to);
}
/**
* Create an instance using the specified range of {@code values}.
*
* <p>Warning: No range checks are performed.
*
* @param values Values.
* @param from Inclusive start of the range.
* @param to Exclusive end of the range.
* @return {@code SumOfLogs} instance.
*/
static SumOfLogs createFromRange(double[] values, int from, int to) {
return Statistics.add(new SumOfLogs(), values, from, to);
}
/**
* Returns an instance populated using the input {@code values}.
*
* <p>The result is {@code NaN} if any of the values is negative.
*
* <p>When the input is an empty array, the result is zero.
*
* @param values Values.
* @return {@code SumOfLogs} instance.
*/
public static SumOfLogs of(int... values) {
return Statistics.add(new SumOfLogs(), values);
}
/**
* Returns an instance populated using the specified range of {@code values}.
*
* <p>The result is {@code NaN} if any of the values is negative.
*
* <p>When the range is empty, the result is zero.
*
* @param values Values.
* @param from Inclusive start of the range.
* @param to Exclusive end of the range.
* @return {@code SumOfLogs} instance.
* @throws IndexOutOfBoundsException if the sub-range is out of bounds
* @since 1.2
*/
public static SumOfLogs ofRange(int[] values, int from, int to) {
Statistics.checkFromToIndex(from, to, values.length);
return createFromRange(values, from, to);
}
/**
* Create an instance using the specified range of {@code values}.
*
* <p>Warning: No range checks are performed.
*
* @param values Values.
* @param from Inclusive start of the range.
* @param to Exclusive end of the range.
* @return {@code SumOfLogs} instance.
*/
static SumOfLogs createFromRange(int[] values, int from, int to) {
return Statistics.add(new SumOfLogs(), values, from, to);
}
/**
* Returns an instance populated using the input {@code values}.
*
* <p>The result is {@code NaN} if any of the values is negative.
*
* <p>When the input is an empty array, the result is zero.
*
* @param values Values.
* @return {@code SumOfLogs} instance.
*/
public static SumOfLogs of(long... values) {
return Statistics.add(new SumOfLogs(), values);
}
/**
* Returns an instance populated using the specified range of {@code values}.
*
* <p>The result is {@code NaN} if any of the values is negative.
*
* <p>When the range is empty, the result is zero.
*
* @param values Values.
* @param from Inclusive start of the range.
* @param to Exclusive end of the range.
* @return {@code SumOfLogs} instance.
* @throws IndexOutOfBoundsException if the sub-range is out of bounds
* @since 1.2
*/
public static SumOfLogs ofRange(long[] values, int from, int to) {
Statistics.checkFromToIndex(from, to, values.length);
return createFromRange(values, from, to);
}
/**
* Create an instance using the specified range of {@code values}.
*
* <p>Warning: No range checks are performed.
*
* @param values Values.
* @param from Inclusive start of the range.
* @param to Exclusive end of the range.
* @return {@code SumOfLogs} instance.
*/
static SumOfLogs createFromRange(long[] values, int from, int to) {
return Statistics.add(new SumOfLogs(), values, from, to);
}
/**
* Updates the state of the statistic to reflect the addition of {@code value}.
*
* @param value Value.
*/
@Override
public void accept(double value) {
delegate.accept(Math.log(value));
}
/**
* Gets the sum of all input values.
*
* <p>When no values have been added, the result is zero.
*
* @return sum of all values.
*/
@Override
public double getAsDouble() {
return delegate.getAsDouble();
}
@Override
public SumOfLogs combine(SumOfLogs other) {
delegate.add(other.delegate);
return this;
}
}