Hi all,
I've found bug in parallel sorting of float / double arrays in the latest JDK.
When float / double values are sorted, additional actions are
required: NaNs must be moved to the end and negative zeros
must be placed before positive zeros.
Current implementation of Arrays.parallelSort(float[] / double [])
invokes parallel merge sort from ArraysParallelSortHelpers class,
but it doesn't arrange NaNs and -0.0.
@Alan, Brent, Laurent
Could you please file a bug?
New optimized version of DualPivotQuicksort (which is under review) works fine
and
doesn't contain this bug. Please, look at my test case to reproduce it.
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import java.util.Random;
public class FailedFloat {
private static final int MAX_N = (1 << 13) /* Arrays.MIN_ARRAY_SORT_GRAN */
+ 10;
public static void main(String[] args) {
float[] a = new float[MAX_N];
random(a);
java.util.Arrays.parallelSort(a);
check(a);
System.out.println("PASSED");
}
private static void random(float[] a) {
Random random = new Random(777);
for (int i = 0; i < MAX_N; i++) {
a[i] = random.nextBoolean() ? -0.0f : 0.0f;
}
}
private static void check(float[] a) {
for (int i = 0; i < a.length - 1; ++i) {
if (Float.floatToRawIntBits(a[i]) == 0 &&
Float.floatToRawIntBits(a[i + 1]) < 0) {
throw new RuntimeException(a[i] + " goes before "+ a[i + 1] + "
at position " + i);
}
}
}
}
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Thank you,
Vladimir
