Bug in parallel sorting of float / double

[Vladimir Yaroslavskiy]

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