Am 03.01.2016 7:49 vorm. schrieb "Ole Ersoy" <ole.er...@gmail.com>:
>
> Hi,
>
> I ran another test using a single parallel loop for array based matrix
vector multiplication. Throughput almost tripled (Test pasted at bottom):
>
> # Run complete. Total time: 00:13:24
>
>
> Benchmark Mode Cnt Score Error
Units
> MultiplyBenchmark.parallelMultiplication thrpt 200 2221.682 ±
48.689 ops/s
> MultiplyBenchmark.singleThreadMultiplication thrpt 200 818.755 ±
9.782 ops/s
>
> public class MultiplyBenchmark {
>
> public static double[] multiplySingleThreaded(double[][] matrix,
double[] vector) {
> return Arrays.stream(matrix)
> .mapToDouble(row -> IntStream.range(0,
row.length).mapToDouble(col -> row[col]
> * vector[col]).sum())
> .toArray();
> }
>
> public static double[] multiplyConcurrent(double[][] matrix, double[]
vector) {
> return Arrays.stream(matrix).parallel()
> .mapToDouble(row -> IntStream.range(0,
row.length).mapToDouble(col -> row[col]
> * vector[col]).sum())
> .toArray();
> }
>
> @State(Scope.Thread)
> public static class Matrix {
> static int size = 10000;
> static double[] vector = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
>
> public static double[][] matrix = new double[size][10];
>
> static {
> for (int i = 0; i < size; i++) {
> matrix[i] = vector.clone();
> }
> }
> }
>
> @Benchmark
> public void singleThreadMultiplication(Matrix m) {
> multiplySingleThreaded(m.matrix, m.vector);
> }
>
> @Benchmark
> public void parallelMultiplication(Matrix m) {
> multiplyConcurrent(m.matrix, m.vector);
>
> }
> }
>
> Cheers,
> Ole
>
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>
I am curious to see how this compares to simple for-loops which I can
imagine help the JIT compiler to do loop unrolling and to make use of
instruction-level parallelism.
Otmar
