dcapwell commented on code in PR #3486:
URL: https://github.com/apache/cassandra/pull/3486#discussion_r1725444268
##########
test/unit/accord/utils/Gens.java:
##########
@@ -89,6 +145,215 @@ public static <T> Gen<T> pick(Map<T, Integer> values)
};
}
+ public static Gen.IntGen pickZipf(int[] array)
+ {
+ if (array == null || array.length == 0)
+ throw new IllegalArgumentException("Empty array given");
+ if (array.length == 1)
+ return ignore -> array[0];
+ BigDecimal[] weights = new BigDecimal[array.length];
+ BigDecimal base = BigDecimal.valueOf(Math.pow(2, array.length));
+ weights[0] = base;
+ for (int i = 1; i < array.length; i++)
+ weights[i] = base.divide(BigDecimal.valueOf(i + 1),
RoundingMode.UP);
+ BigDecimal totalWeights = Stream.of(weights).reduce(BigDecimal.ZERO,
BigDecimal::add);
+
+ return rs -> {
+ BigDecimal value =
BigDecimal.valueOf(rs.nextDouble()).multiply(totalWeights);
+ for (int i = 0; i < weights.length; i++)
+ {
+ value = value.subtract(weights[i]);
+ if (value.compareTo(BigDecimal.ZERO) <= 0)
+ return array[i];
+ }
+ return array[array.length - 1];
+ };
+ }
+
+ public static Gen.LongGen pickZipf(long[] array)
+ {
+ if (array == null || array.length == 0)
+ throw new IllegalArgumentException("Empty array given");
+ if (array.length == 1)
+ return ignore -> array[0];
+ BigDecimal[] weights = new BigDecimal[array.length];
+ BigDecimal base = BigDecimal.valueOf(Math.pow(2, array.length));
+ weights[0] = base;
+ for (int i = 1; i < array.length; i++)
+ weights[i] = base.divide(BigDecimal.valueOf(i + 1),
RoundingMode.UP);
+ BigDecimal totalWeights = Stream.of(weights).reduce(BigDecimal.ZERO,
BigDecimal::add);
+
+ return rs -> {
+ BigDecimal value =
BigDecimal.valueOf(rs.nextDouble()).multiply(totalWeights);
+ for (int i = 0; i < weights.length; i++)
+ {
+ value = value.subtract(weights[i]);
+ if (value.compareTo(BigDecimal.ZERO) <= 0)
+ return array[i];
+ }
+ return array[array.length - 1];
+ };
+ }
+
+ public static <T> Gen<T> pickZipf(T... array)
+ {
+ return pickZipf(Arrays.asList(array));
+ }
+
+ public static <T> Gen<T> pickZipf(List<T> array)
+ {
+ if (array == null || array.isEmpty())
+ throw new IllegalArgumentException("Empty array given");
+ if (array.size() == 1)
+ return ignore -> array.get(0);
+ BigDecimal[] weights = new BigDecimal[array.size()];
+ BigDecimal base = BigDecimal.valueOf(Math.pow(2, array.size()));
+ weights[0] = base;
+ for (int i = 1; i < array.size(); i++)
+ weights[i] = base.divide(BigDecimal.valueOf(i + 1),
RoundingMode.UP);
+ BigDecimal totalWeights = Stream.of(weights).reduce(BigDecimal.ZERO,
BigDecimal::add);
+
+ return rs -> {
+ BigDecimal value =
BigDecimal.valueOf(rs.nextDouble()).multiply(totalWeights);
+ for (int i = 0; i < weights.length; i++)
+ {
+ value = value.subtract(weights[i]);
+ if (value.compareTo(BigDecimal.ZERO) <= 0)
+ return array.get(i);
+ }
+ return array.get(array.size() - 1);
+ };
+ }
+
+ public static Gen<Gen.IntGen> mixedDistribution(int minInclusive, int
maxExclusive)
+ {
+ int domainSize = (maxExclusive - minInclusive + 1);
+ if (domainSize < 0)
+ throw new IllegalArgumentException("Range is too large; min=" +
minInclusive + ", max=" + maxExclusive);
+ int[] array, indexes;
+ if (domainSize > 200) // randomly selected
+ {
+ int numBuckets = 10;
+ int delta = domainSize / numBuckets;
+ array = new int[numBuckets];
+ for (int i = 0; i < numBuckets; i++)
+ array[i] = minInclusive + i * delta;
+ indexes = IntStream.range(0, array.length).toArray();
+ }
+ else
+ {
+ array = IntStream.range(minInclusive, maxExclusive).toArray();
+ indexes = null;
+ }
+ return rs -> {
+ switch (rs.nextInt(0, 2))
Review Comment:
this isn't 100% in-sync with accord due to a missing set of random methods I
didn't care to backport... so this is missing 2 other "distributions"
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