Hi Xing,
I think this is related to a issue recently raised on JIRA:
http://jira.codehaus.org/browse/XTENLANG-1229
You might want to comment there as well.
cheers
ganesh
--- On Tue, 13/4/10, Liu, Xing <xing....@gatech.edu> wrote:
> From: Liu, Xing <xing....@gatech.edu>
> Subject: [X10-users] Performance of foreach
> To: "x10-users" <x10-users@lists.sourceforge.net>
> Date: Tuesday, 13 April, 2010, 10:24 PM
> Hi,
>
>
> We used the following code to test the performance of
> foreach.
> add1() is a sequential code.
> in add2(), we use foreach, and let X10 to
> partition workloads.
> and in add3(), we partition the workloads by
> ourselves.
>
> We use c++ backend, and run the code as
> # env X10_NTHREADS=2 runx10 ./Test_foreach
>
> The performance:
>
> time of add1() = 32.3 ms
> time of add2() = 3277.98 ms
> time of add3() = 18.33 ms
>
> It is surprising that add2() is 100 times slower than
> add1(). Is someone knows the reason? Thanks.
>
>
> // Test_foreach.x10
>
> def add1()
> {
> for ((i) in 0..size-1)
> {
> data(i) += 5;
> }
> }
>
> def add2()
> {
> finish foreach ((i) in 0..size-1)
> {
> data(i) += 5;
> }
> }
>
> def add3()
> {
> var numThreads: Int = 2;
> val mySize = size/numThreads;
> finish foreach ((p) in 0..numThreads-1)
> {
> for ((i) in
> p*mySize..(p+1)*mySize-1)
> {
> data(i) += 5;
> }
> }
> }
>
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