Centre Blaise Pascal » Bench4GPU

/* Simple Discrete Fourier Transform implemented in C and OpenACC/C */

/* compilation with : gcc -O3 -fopenacc -foffload=nvptx-none -foffload="-O3 -misa=sm_35 -lm" -o MyDFT_openacc MyDFT_openacc.c -lm */

#include <math.h>

#include <stdio.h>

#include <stdlib.h>

#include <openacc.h>

#include <sys/time.h>

#define PI 3.141592653589793

#define MYFLOAT float

void MyDFT(MYFLOAT *A, MYFLOAT *B, MYFLOAT *a, MYFLOAT *b,int size)

{

  for (uint j=0;j<size;j++)

    {

      MYFLOAT At=0.,Bt=0.;

      for (uint i=0; i<size;i++)

        {

          At+=a[i]*cos(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size)-b[i]*sin(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size);

          Bt+=a[i]*sin(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size)+b[i]*cos(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size);

        }

      A[j]=At;

      B[j]=Bt;

    }

}

void MyDFTOpenACC(MYFLOAT *A, MYFLOAT *B, MYFLOAT *a, MYFLOAT *b,int size)

{

#pragma acc data copy(a[0:size],b[0:size],A[0:size],B[0:size])

#pragma acc parallel loop

    for (uint j=0;j<size;j++)

      {

        MYFLOAT At=0.,Bt=0.;

#pragma acc seq reduction(+: At) reduction(+: Bt)

        {

        for (uint i=0; i<size;i++)

          {

            At+=a[i]*cos(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size)-b[i]*sin(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size);

            Bt+=a[i]*sin(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size)+b[i]*cos(2.*PI*(MYFLOAT)(j*i)/(MYFLOAT)size);

          }

        A[j]=At;

        B[j]=Bt;

      }

      }

}

int main(int argc,char *argv[])

{

  float *a,*b,*A,*B;

  int size=1024;

  struct timeval tv1,tv2;

  if (argc > 1) {

    size=(int)atoll(argv[1]);

  }

  else {

    printf("\n\tPi : Estimate DFT\n\n\t\t#1 : size (default 1024)\n\n");

  }

  a=(MYFLOAT*)malloc(size*sizeof(MYFLOAT));

  b=(MYFLOAT*)malloc(size*sizeof(MYFLOAT));

  A=(MYFLOAT*)malloc(size*sizeof(MYFLOAT));

  B=(MYFLOAT*)malloc(size*sizeof(MYFLOAT));

  for (int i=0;i<size;i++)

    {

      a[i]=1.;

      b[i]=1.;

      A[i]=0.;

      A[i]=0.;

    }

  gettimeofday(&tv1, NULL);

  MyDFT(A,B,a,b,size);

  gettimeofday(&tv2, NULL);

  MYFLOAT elapsed=(MYFLOAT)((tv2.tv_sec-tv1.tv_sec) * 1000000L +

                            (tv2.tv_usec-tv1.tv_usec))/1000000;

  gettimeofday(&tv1, NULL);

  MyDFTOpenACC(A,B,a,b,size);

  gettimeofday(&tv2, NULL);

  MYFLOAT elapsedOpenACC=(MYFLOAT)((tv2.tv_sec-tv1.tv_sec) * 1000000L +

                                   (tv2.tv_usec-tv1.tv_usec))/1000000;

  /* printf("A=["); */

  /* for (int i=0;i<size;i++) */

  /*   { */

  /*     printf("%.2f ",A[i]); */

  /*   } */

  /* printf(" ]\n\n"); */

  /* printf("B=["); */

  /* for (int i=0;i<size;i++) */

  /*   { */

  /*     printf("%.2f ",B[i]); */

  /*   } */

  /* printf(" ]\n\n"); */

  printf("\nA[0]=%.3f A[%i]=%.3f\n",A[0],size-1,A[size-1]);

  printf("B[0]=%.3f B[%i]=%.3f\n\n",B[0],size-1,B[size-1]);

  printf("Elapsed Time: %.3f\n",elapsed);

  printf("OpenACC Elapsed Time: %.3f\n",elapsedOpenACC);

  printf("NaiveRate: %.i\n",(int)((float)size/elapsed));

  printf("OpenACCRate: %.i\n",(int)((float)size/elapsedOpenACC));

  free(a);

  free(b);

  free(A);

  free(B);

}