Using SVM for Intel Graphics Technology

[Mathieu_D]

Hi,

I'm writing a benchmark to compare different technologies and their performance accross various platforms (on Linux). One of the platform is an Intel Broadwell-H  (Core i7-5775C with integrated GPU Iris Pro 6200), so I'm testing the various ways to offload a code on my GPU using Cilk Plus. Right now, I'm trying to use SVM so I followed this tutorial but I'm facing some problems. Here's my code :

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <cilk/cilk.h>
#include <gfx/gfx_rt.h>

#define SIZE 64

int main(){
  int * in = (int*)_GFX_svm_alloc(sizeof(int)*SIZE);

#pragma offload target(gfx)
  _Cilk_for (int i = 0; i < SIZE; i++){
    in = 1;
  }

  for (int i = 0; i < SIZE; i++){
    assert(in == 1);
  }

  _GFX_svm_free(in);
  return 0;
}

Then I compile with

 - $ icc -qoffload-svm test.c
test.c(12): error: *GFX* pointer variable "in" in this offload region must be specified in an in/out/inout/nocpy clause
  #pragma offload target(gfx)
  ^

compilation aborted for test.c (code 2)

I thought maybe SVM is not allowed on all patforms, so compiled with

- $ icc -qoffload-arch=broadwell -qoffload-svm test.c
- $ ./a.out
libva info: VA-API version 0.99.0
libva info: va_getDriverName() returns 0
libva info: User requested driver 'iHD'
libva info: Trying to open /opt/intel/mediasdk/lib64/iHD_drv_video.so
libva info: Found init function __vaDriverInit_0_32
libva info: va_openDriver() returns 0
a.out test.c:18: main: Assertion 'in == 1' failed.
Abandon (core dumped)

So I guess specifying the platform helps to compile, but the execution failed.

If I change the pragma adding inout(in : length(SIZE)), the compilation/execution works well with the first one, but with the second one we have the same execution problem. The point is : I don't want to add the inout clause, I shouldn't have to. I assume my compilation line is wrong but I can't say in which way.

So my question is : do you see something wrong in my code/compilation ?

Thanks a lot for your time,

Mathieu

[Barry_T_Intel]

You're more likely to get a response to questions about offloading to the GPU in the Intel C++ Compiler forum.