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aherbert pushed a commit to branch master
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commit 11b8d250fc5731c3319e69dc441e22e8dd9474fb
Author: Alex Herbert <aherb...@apache.org>
AuthorDate: Sat Jul 17 12:03:14 2021 +0100
Update DiscreteUniformSampler to match UniformLongSampler
Fixed sampler does not require a RNG reference.
Add test for a small range against a reference RNG.
Add test for a power of 2 range against a reference RNG.
Add test for a large range against the same RNG. Output outside the
range should be ignored.
---
.../distribution/DiscreteUniformSampler.java | 16 ++--
.../sampling/distribution/UniformLongSampler.java | 2 +-
.../distribution/DiscreteUniformSamplerTest.java | 97 +++++++++++++++++-----
.../distribution/UniformLongSamplerTest.java | 2 +-
4 files changed, 90 insertions(+), 27 deletions(-)
diff --git
a/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSampler.java
b/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSampler.java
index 6a39aea..7190fc3 100644
---
a/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSampler.java
+++
b/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSampler.java
@@ -87,12 +87,11 @@ public class DiscreteUniformSampler
private final int value;
/**
- * @param rng Generator of uniformly distributed random numbers.
* @param value The value.
*/
- FixedDiscreteUniformSampler(UniformRandomProvider rng,
- int value) {
- super(rng);
+ FixedDiscreteUniformSampler(int value) {
+ // No requirement for the RNG
+ super(null);
this.value = value;
}
@@ -102,6 +101,12 @@ public class DiscreteUniformSampler
}
@Override
+ public String toString() {
+ // No RNG to include in the string
+ return "Uniform deviate [X=" + value + "]";
+ }
+
+ @Override
public SharedStateDiscreteSampler
withUniformRandomProvider(UniformRandomProvider rng) {
// No requirement for the RNG
return this;
@@ -305,7 +310,6 @@ public class DiscreteUniformSampler
return offset + sampler.sample();
}
- /** {@inheritDoc} */
@Override
public String toString() {
return sampler.toString();
@@ -379,7 +383,7 @@ public class DiscreteUniformSampler
// This must be done first as the methods to handle lower == 0
// do not handle upper == 0.
if (upper == lower) {
- return new FixedDiscreteUniformSampler(rng, lower);
+ return new FixedDiscreteUniformSampler(lower);
}
// Algorithms to ignore the lower bound if it is zero.
diff --git
a/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/UniformLongSampler.java
b/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/UniformLongSampler.java
index 2eb05a1..28766ac 100644
---
a/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/UniformLongSampler.java
+++
b/commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/UniformLongSampler.java
@@ -237,7 +237,7 @@ public abstract class UniformLongSampler implements
SharedStateLongSampler {
/**
* @param rng Generator of uniformly distributed random numbers.
*/
- private UniformLongSampler(UniformRandomProvider rng) {
+ UniformLongSampler(UniformRandomProvider rng) {
this.rng = rng;
}
diff --git
a/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSamplerTest.java
b/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSamplerTest.java
index 053c268..98bdfa3 100644
---
a/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSamplerTest.java
+++
b/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/DiscreteUniformSamplerTest.java
@@ -63,23 +63,49 @@ public class DiscreteUniformSamplerTest {
final UniformRandomProvider rng1 =
RandomSource.SPLIT_MIX_64.create(0L);
final UniformRandomProvider rng2 =
RandomSource.SPLIT_MIX_64.create(0L);
final SharedStateDiscreteSampler sampler =
DiscreteUniformSampler.of(rng2, lower, upper);
- for (int i = 0; i < 5; i++) {
+ for (int i = 0; i < 10; i++) {
Assert.assertEquals(rng1.nextInt(), sampler.sample());
}
}
+ /**
+ * Test samples with a non-power of 2 range.
+ * The output should be the same as the long values produced from a RNG
+ * based on o.a.c.rng.core.BaseProvider as the rejection algorithm is
+ * the same.
+ */
+ @Test
+ public void testSamplesWithSmallNonPowerOf2Range() {
+ final int upper = 257;
+ for (final int lower : new int[] {-13, 0, 13}) {
+ final int n = upper - lower + 1;
+ final UniformRandomProvider rng1 =
RandomSource.SPLIT_MIX_64.create(0L);
+ final UniformRandomProvider rng2 =
RandomSource.SPLIT_MIX_64.create(0L);
+ final SharedStateDiscreteSampler sampler =
DiscreteUniformSampler.of(rng2, lower, upper);
+ for (int i = 0; i < 10; i++) {
+ Assert.assertEquals(lower + rng1.nextInt(n), sampler.sample());
+ }
+ }
+ }
+
+ /**
+ * Test samples with a power of 2 range.
+ * This tests the minimum and maximum output should be the range limits.
+ */
@Test
public void testSamplesWithPowerOf2Range() {
final UniformRandomProvider rngZeroBits = new IntProvider() {
@Override
public int next() {
+ // No bits
return 0;
}
};
final UniformRandomProvider rngAllBits = new IntProvider() {
@Override
public int next() {
- return 0xffffffff;
+ // All bits
+ return -1;
}
};
@@ -87,7 +113,7 @@ public class DiscreteUniformSamplerTest {
DiscreteUniformSampler sampler;
// The upper range for a positive integer is 2^31-1. So the max
positive power of
// 2 is 2^30. However the sampler should handle a bit shift of 31 to
create a range
- // of Integer.MIN_VALUE (0x80000000) as this is a power of 2 as an
unsigned int (2^31).
+ // of Integer.MIN_VALUE as this is a power of 2 as an unsigned int
(2^31).
for (int i = 0; i < 32; i++) {
final int range = 1 << i;
final int upper = lower + range - 1;
@@ -98,6 +124,50 @@ public class DiscreteUniformSamplerTest {
}
}
+ /**
+ * Test samples with a power of 2 range.
+ * This tests the output is created using a bit shift.
+ */
+ @Test
+ public void testSamplesWithPowerOf2RangeIsBitShift() {
+ final int lower = 0;
+ SharedStateDiscreteSampler sampler;
+ // Power of 2 sampler used for a bit shift of 1 to 31.
+ for (int i = 1; i <= 31; i++) {
+ // Upper is inclusive so subtract 1
+ final int upper = (1 << i) - 1;
+ final int shift = 32 - i;
+ final UniformRandomProvider rng1 =
RandomSource.SPLIT_MIX_64.create(0L);
+ final UniformRandomProvider rng2 =
RandomSource.SPLIT_MIX_64.create(0L);
+ sampler = DiscreteUniformSampler.of(rng2, lower, upper);
+ for (int j = 0; j < 10; j++) {
+ Assert.assertEquals(rng1.nextInt() >>> shift,
sampler.sample());
+ }
+ }
+ }
+
+ /**
+ * Test samples with a large non-power of 2 range.
+ * This tests the large range algorithm uses a rejection method.
+ */
+ @Test
+ public void testSamplesWithLargeNonPowerOf2RangeIsRejectionMethod() {
+ // Create a range bigger than 2^63
+ final int upper = Integer.MAX_VALUE / 2 + 1;
+ final int lower = Integer.MIN_VALUE / 2 - 1;
+ final UniformRandomProvider rng1 =
RandomSource.SPLIT_MIX_64.create(0L);
+ final UniformRandomProvider rng2 =
RandomSource.SPLIT_MIX_64.create(0L);
+ final SharedStateDiscreteSampler sampler =
DiscreteUniformSampler.of(rng2, lower, upper);
+ for (int i = 0; i < 10; i++) {
+ // Get the expected value by the rejection method
+ long expected;
+ do {
+ expected = rng1.nextInt();
+ } while (expected < lower || expected > upper);
+ Assert.assertEquals(expected, sampler.sample());
+ }
+ }
+
@Test
public void testOffsetSamplesWithNonPowerOf2Range() {
assertOffsetSamples(257);
@@ -197,6 +267,8 @@ public class DiscreteUniformSamplerTest {
@Test
public void testSampleUniformityWithPowerOf2Range() {
// Test using a RNG that outputs a counter of integers.
+ // The n most significant bits will be represented uniformly over a
+ // sequence that is a 2^n long.
final UniformRandomProvider rng = new IntProvider() {
private int bits = 0;
@@ -259,34 +331,22 @@ public class DiscreteUniformSamplerTest {
Assert.assertEquals("Sample should be produced from 2nd value", 2,
value[0]);
}
- /**
- * Test the SharedStateSampler implementation.
- */
@Test
public void testSharedStateSamplerWithSmallRange() {
testSharedStateSampler(5, 67);
}
- /**
- * Test the SharedStateSampler implementation.
- */
@Test
public void testSharedStateSamplerWithLargeRange() {
// Set the range so rejection below or above the threshold occurs with
approximately p=0.25
testSharedStateSampler(Integer.MIN_VALUE / 2 - 1, Integer.MAX_VALUE /
2 + 1);
}
- /**
- * Test the SharedStateSampler implementation.
- */
@Test
public void testSharedStateSamplerWithPowerOf2Range() {
testSharedStateSampler(0, 31);
}
- /**
- * Test the SharedStateSampler implementation.
- */
@Test
public void testSharedStateSamplerWithRangeOf1() {
testSharedStateSampler(9, 9);
@@ -330,16 +390,15 @@ public class DiscreteUniformSamplerTest {
}
/**
- * Test the toString method. This is added to ensure coverage as the
factory constructor
- * used in other tests does not create an instance of the wrapper class.
+ * Test the toString method contains the term "uniform". This is true of
all samplers
+ * even for a fixed sample from a range of 1.
*
* @param lower Lower.
* @param upper Upper.
*/
private static void assertToString(int lower, int upper) {
final UniformRandomProvider rng = RandomSource.SPLIT_MIX_64.create(0L);
- final DiscreteUniformSampler sampler =
- new DiscreteUniformSampler(rng, lower, upper);
+ final DiscreteUniformSampler sampler = new DiscreteUniformSampler(rng,
lower, upper);
Assert.assertTrue(sampler.toString().toLowerCase(Locale.US).contains("uniform"));
}
}
diff --git
a/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/UniformLongSamplerTest.java
b/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/UniformLongSamplerTest.java
index 33ced6b..55b0578 100644
---
a/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/UniformLongSamplerTest.java
+++
b/commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/UniformLongSamplerTest.java
@@ -55,7 +55,7 @@ public class UniformLongSamplerTest {
final long lower = upper;
final UniformRandomProvider rng = RandomSource.SPLIT_MIX_64.create();
final UniformLongSampler sampler = UniformLongSampler.of(rng, lower,
upper);
- for (int i = 0; i < 10; i++) {
+ for (int i = 0; i < 5; i++) {
Assert.assertEquals(lower, sampler.sample());
}
}
