To use FPU

[GHui]

The following code is to use FPU. I run it on E5-2620. It only upto 2 GFlops. If I want to 2*8 GFlops, how could I code program?

Any help will be appreciated.

void* test_pd_avx()
{
  double x[4]={12.02,14.34,34.23,234.34};
  double y[4]={123.234,234.234,675.34,3453.345};
  __m256d mx=_mm256_load_pd(x);
  __m256d my=_mm256_load_pd(y);
  for(;;)
  {
    __m256d mz=_mm256_mul_pd(mx,my);   
  }
}

The Compiler Option: icc test.c -O0

[Bernard]

Ok:)

[SergeyKostrov]

>>...The Compiler Option: icc test.c -O0 Try performance evaluations with -O2 and -O3 compiler options.

[GHui]

Sergey Kostrov wrote:

>>...The Compiler Option: icc test.c -O0

Try performance evaluations with -O2 and -O3 compiler options.

-O2 or -O3 will optimize the code, and it's behavior undefined.