Dear list,
I'm writing an X10 application which is suitable to parallelise. I work on
an Intel Quad Core CPU and want to use 4 Threads. I changed X10_NTHREADS
accordingly. The results are ok, I got almost a linear speedup at the
calculations. But there is one problem. I also have to read a big imagefile
at the beginning and this takes a lot more time, when I use more Threads.
$ x10c++ -STATIC_CALLS -O -NO_CHECKS -o x10app Code.x10
$ export X10_NTHREADS=1
$ ./x10app
read image data: 2336 ms
calculation: 8290 ms
$ export X10_NTHREADS=4
$ ./x10app
read image data: 6129 ms
calculation: 2330 ms
Here is a code snippet of reading the image:
comp1 = new Array[Int]((0..(height-1))*(0..(width-1)));
comp2 = new Array[Int]((0..(height-1))*(0..(width-1)));
comp3 = new Array[Int]((0..(height-1))*(0..(width-1)));
for([i,j] in comp1) {
comp1(i,j) = filereader.readByte() & 0xFF;
comp2(i,j) = filereader.readByte() & 0xFF;
comp3(i,j) = filereader.readByte() & 0xFF;
}
I don't understand, maybe someone can help me?
Sascha
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