Hi Otmar,
On 01/02/2016 10:33 AM, Otmar Ertl wrote:
On Sat, Jan 2, 2016 at 4:38 AM, Ole Ersoy <ole.er...@gmail.com> wrote:
Hi,
Hope ya'll are having an awesome new year!
Some matrix operations, like createRealIdentityMatrix can be turned into one
liners like this:
IntStream.range(0, dimension).forEach(i -> m.setEntry(i, i, 1.0));
And can be performed in parallel like this:
IntStream.range(0, dimension).parallel().forEach(i -> m.setEntry(i,
i, 1.0));
Applying that approach in general we could probably create a
ParallelXxxRealMatrix fairly easily. Just thought I'd float the idea.
Cheers,
Ole
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Once we go for Java 8, yes. However, all these constructs have some
overhead. I doubt that the naive parallelization using parallel() is
faster than the sequential counterpart, especially for operations such
as matrix initializations.
I'm sure it depends...But just to find out whether there is any merit to it I
ran the identity matrix code single threaded and parallel (With JMH), and these
were the results (On my HP Envy laptop 8 cores):
# Run complete. Total time: 00:14:08
Benchmark Mode Cnt Score Error Units
MyBenchmark.parallelIdentity thrpt 200 18875.739 ± 400.382 ops/s
MyBenchmark.singleThreadIdentity thrpt 200 11046.079 ± 130.713 ops/s
So almost twice the throughput with parallel(). This was on a 20K X 20K
matrix. I'll paste the test code at the bottom.
A more efficient parallel implementation
would require the definition of a Spliterator that divides an
operation into less but larger chunks of work in order to amortize
synchronization costs. In general, the implementation of efficient and
well scaling parallel matrix operations requires more work than
writing just a single line of code.
I'm sure you are right. I'm going to test array based matrix vector
multiplication next. I'm curious to see what happens once some basic
operations are added.
Cheers,
Ole
public class IdentityBenchmark {
@State(Scope.Thread)
public static class Identity {
public int dimension = 20000;
public double[][] m = new double[dimension][dimension];
}
@Benchmark
public void singleThreadIdentity(Identity m) {
IntStream.range(0, m.dimension).forEach(i -> m.m[i][i] = 1.0);
}
@Benchmark
public void parallelIdentity(Identity m) {
IntStream.range(0, m.dimension).parallel().forEach(i -> m.m[i][i] =
1.0);
}
}
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