Vector performance issue.

[Andrii Lomakin]

Hi,
I have the same problem during calculation of Eucledian distance in my
project too.
Writing just to confirm that it is not a single case and I have got the
same result during profiling.

On Sat, Sep 16, 2023 at 9:50 PM Jake Luciani <jake at apache.org> wrote:

> Hi,
>
> I've been struggling with a problem recently using the vector api.
> It appears as reduceLanes is not using the intrinsic.
>
>           ns  percent  samples  top
>   ----------  -------  -------  ---
>  13240151836   88.21%     1324
> jdk.incubator.vector.FloatVector.reduceLanesTemplate
>   1349991099    8.99%      135
> jdk.incubator.vector.FloatVector.lanewiseTemplate
>
> I've tested openjdk 20 and 21 and my machine has AVX512.
>
>  When I PrintIntrinsics I see the following (among others):
>
>   ** missing constant: opr=RShiftI vclass=ConP etype=ConP vlen=ConI
>
> I've included a JMH benchmark that reproduces the issue.
>
> -Jake
>
> import jdk.incubator.vector.FloatVector;
> import jdk.incubator.vector.IntVector;
> import jdk.incubator.vector.ShortVector;
> import jdk.incubator.vector.VectorOperators;
> import org.openjdk.jmh.annotations.*;
> import org.openjdk.jmh.infra.Blackhole;
>
> import java.util.concurrent.ThreadLocalRandom;
> import java.util.concurrent.TimeUnit;
>
>
> @Warmup(iterations = 1, time = 5)
> @Measurement(iterations = 3, time = 5)
> @Fork(warmups = 1, value = 1, jvmArgsPrepend = {
>         "--add-modules=jdk.incubator.vector",
>         "--enable-preview"})
> public class VectorPerfBench
> {
>     private static final int SIZE = 8192;
>     private static final IntVector BF16_BYTE_SHIFT =
> IntVector.broadcast(IntVector.SPECIES_512, 16);
>
>     public static short float32ToBFloat16(float f) {
>         return (short) (Float.floatToIntBits(f) >> 16);
>     }
>     @State(Scope.Benchmark)
>     public static class Parameters {
>         final short[] s1 = new short[SIZE];
>         final short[] s2 = new short[SIZE];
>
>         public Parameters() {
>             for (int i = 0; i < SIZE; i++) {
>                 s1[i] =
> float32ToBFloat16(ThreadLocalRandom.current().nextFloat());
>                 s2[i] =
> float32ToBFloat16(ThreadLocalRandom.current().nextFloat());
>             }
>         }
>     }
>
>     @Benchmark
>     @OutputTimeUnit(TimeUnit.MILLISECONDS)
>     @BenchmarkMode(Mode.Throughput)
>     public void bfloatDot(Parameters p, Blackhole bh) {
>         FloatVector acc = FloatVector.zero(FloatVector.SPECIES_512);
>         for (int i = 0; i < SIZE; i += FloatVector.SPECIES_512.length()) {
>
>             var f1 = ShortVector.fromArray(ShortVector.SPECIES_256, p.s1,
> i)
>                     .convertShape(VectorOperators.ZERO_EXTEND_S2I,
> IntVector.SPECIES_512, 0)
>                     .lanewise(VectorOperators.LSHL, BF16_BYTE_SHIFT)
>                     .reinterpretAsFloats();
>
>             var f2 = ShortVector.fromArray(ShortVector.SPECIES_256, p.s2,
> i)
>                     .convertShape(VectorOperators.ZERO_EXTEND_S2I,
> IntVector.SPECIES_512, 0)
>                     .lanewise(VectorOperators.LSHL, BF16_BYTE_SHIFT)
>                     .reinterpretAsFloats();
>
>             acc = acc.add(f1.mul(f2));
>         }
>
>         bh.consume(acc.reduceLanes(VectorOperators.ADD));
>     }
>
>     public static void main(String[] args) throws Exception {
>         org.openjdk.jmh.Main.main(args);
>     }
> }
>


-- 
Best regards,
Andrii Lomakin.
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