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aherbert pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-statistics.git
commit dec22784a51aeb0899750a69f81736f2bde0f001
Author: Alex Herbert <aherb...@apache.org>
AuthorDate: Wed Dec 27 22:59:42 2023 +0000
Refactor division for the integer mean
---
.../commons/statistics/descriptive/IntMath.java | 20 ++++++++++++++
.../commons/statistics/descriptive/IntMean.java | 5 ++--
.../commons/statistics/descriptive/LongMean.java | 5 ++--
.../statistics/descriptive/IntMathTest.java | 31 ++++++++++++++++++++++
.../commons/statistics/descriptive/TestHelper.java | 2 ++
src/conf/checkstyle/checkstyle-suppressions.xml | 2 +-
6 files changed, 58 insertions(+), 7 deletions(-)
diff --git
a/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMath.java
b/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMath.java
index 2309750..fd5c164 100644
---
a/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMath.java
+++
b/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMath.java
@@ -18,6 +18,7 @@ package org.apache.commons.statistics.descriptive;
import java.math.BigDecimal;
import java.math.BigInteger;
+import org.apache.commons.numbers.core.DD;
/**
* Support class for integer math.
@@ -35,6 +36,8 @@ final class IntMath {
private static final int EXP_SHIFT = 52;
/** 0.5. */
private static final double HALF = 0.5;
+ /** 2^53. */
+ private static final long TWO_POW_53 = 1L << 53;
/** No instances. */
private IntMath() {}
@@ -388,4 +391,21 @@ final class IntMath {
}
return y;
}
+
+ /**
+ * Divide value {@code x} by the count {@code n}.
+ *
+ * @param x Value.
+ * @param n Count.
+ * @return the quotient
+ */
+ static double divide(Int128 x, long n) {
+ final DD a = x.toDD();
+ if (n < TWO_POW_53) {
+ // n is a representable double
+ return a.divide(n).doubleValue();
+ }
+ // Extended precision divide when n > 2^53
+ return a.divide(DD.of(n)).doubleValue();
+ }
}
diff --git
a/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMean.java
b/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMean.java
index 0713047..9bd384d 100644
---
a/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMean.java
+++
b/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/IntMean.java
@@ -130,9 +130,8 @@ public final class IntMean implements IntStatistic,
StatisticAccumulator<IntMean
if (n < SMALL_N) {
return (double) sum.lo64() / n;
}
- // Extended precision.
- // Could divide by DD.of(n) when |n| > 2^53.
- return sum.toDD().divide(n).doubleValue();
+ // Extended precision
+ return IntMath.divide(sum, n);
}
@Override
diff --git
a/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/LongMean.java
b/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/LongMean.java
index 3f84a9e..37b2095 100644
---
a/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/LongMean.java
+++
b/commons-statistics-descriptive/src/main/java/org/apache/commons/statistics/descriptive/LongMean.java
@@ -127,9 +127,8 @@ public final class LongMean implements LongStatistic,
StatisticAccumulator<LongM
if (sum.hi64() == 0 && Math.abs(sum.lo64()) < SMALL_SUM) {
return (double) sum.lo64() / n;
}
- // Extended precision.
- // Could divide by DD.of(n) when |n| > 2^53.
- return sum.toDD().divide(n).doubleValue();
+ // Extended precision
+ return IntMath.divide(sum, n);
}
@Override
diff --git
a/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/IntMathTest.java
b/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/IntMathTest.java
index ccc4416..b16baff 100644
---
a/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/IntMathTest.java
+++
b/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/IntMathTest.java
@@ -17,13 +17,18 @@
package org.apache.commons.statistics.descriptive;
+import java.math.BigDecimal;
import java.math.BigInteger;
+import java.math.MathContext;
+import java.util.Arrays;
import java.util.function.Supplier;
import java.util.stream.DoubleStream;
import java.util.stream.LongStream;
import java.util.stream.LongStream.Builder;
import java.util.stream.Stream;
import org.apache.commons.rng.UniformRandomProvider;
+import org.apache.commons.statistics.distribution.DoubleTolerances;
+import org.apache.commons.statistics.distribution.TestUtils;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
@@ -203,4 +208,30 @@ class IntMathTest {
Assertions.assertEquals(0, Math.toIntExact(Math.round(x)));
Assertions.assertThrowsExactly(ArithmeticException.class, () ->
IntMath.toIntExact(x));
}
+
+ @ParameterizedTest
+ @MethodSource
+ void testInt128Divide(long a, long b, long n) {
+ final Int128 x = new Int128(a, b);
+ final BigInteger bi =
BigInteger.valueOf(a).shiftLeft(Long.SIZE).add(BigInteger.valueOf(b));
+ final double expected = new BigDecimal(bi).divide(
+ new BigDecimal(n), MathContext.DECIMAL128).doubleValue();
+ // This may require a 1 ulp tolerance; log the seed to allow repeats
+ TestUtils.assertEquals(expected, IntMath.divide(x, n),
DoubleTolerances.equals(),
+ () -> String.format("(2^64 * %d + %d) / %d; Seed=%s",
+ a, b, n, Arrays.toString(TestHelper.createRNGSeed())));
+ }
+
+ static Stream<Arguments> testInt128Divide() {
+ final UniformRandomProvider rng =
TestHelper.createRNG(TestHelper.createRNGSeed());
+ final Stream.Builder<Arguments> builder = Stream.builder();
+ for (int i = 0; i < 100; i++) {
+ final long a = rng.nextLong();
+ final long b = rng.nextLong();
+ final long n = rng.nextLong();
+ builder.accept(Arguments.of(a, b, n >>> 1));
+ builder.accept(Arguments.of(a, b, n >>> 43));
+ }
+ return builder.build();
+ }
}
diff --git
a/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/TestHelper.java
b/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/TestHelper.java
index 22c385d..a1a57e5 100644
---
a/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/TestHelper.java
+++
b/commons-statistics-descriptive/src/test/java/org/apache/commons/statistics/descriptive/TestHelper.java
@@ -218,6 +218,8 @@ final class TestHelper {
/**
* Creates a seed for the RNG.
+ * This is the same seed within an invocation of the JVM; seeds will be
different
+ * across JVM instances.
*
* @return the seed
* @see #createRNG(long[])
diff --git a/src/conf/checkstyle/checkstyle-suppressions.xml
b/src/conf/checkstyle/checkstyle-suppressions.xml
index c363f46..dd425bc 100644
--- a/src/conf/checkstyle/checkstyle-suppressions.xml
+++ b/src/conf/checkstyle/checkstyle-suppressions.xml
@@ -41,5 +41,5 @@
<suppress checks="MethodLength"
files=".*[/\\]WilcoxonSignedRankTestTest.java" />
<suppress checks="IllegalCatch" files=".*[/\\]TestHelper.java"
lines="390-450" />
<suppress checks="IllegalCatch" files=".*[/\\]BaseStatisticTest.java"
lines="280-400" />
- <suppress checks="IllegalCatch" files=".*[/\\]IntMathTest.java"
lines="165-175" />
+ <suppress checks="IllegalCatch" files=".*[/\\]IntMathTest.java"
lines="170-185" />
</suppressions>
