Actual source code: PetscMemcpy.c
petsc-3.7.1 2016-05-15
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      2: #include <petscsys.h>
      3: #include <petsctime.h>

      7: int main(int argc,char **argv)
      8: {
      9:   PetscLogDouble x,y,z;
     10:   int            i,ierr;
     11:   PetscScalar    *A,*B;

     13:   PetscInitialize(&argc,&argv,0,0);

     15:   PetscMalloc1(8000000,&A);
     16:   PetscMalloc1(8000000,&B);

     18:   for (i=0; i<8000000; i++) {
     19:     A[i] = i%61897;
     20:     B[i] = i%61897;
     21:   }
     22:   /* To take care of paging effects */
     23:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     24:   PetscTime(&x);

     26:   PetscTime(&x);
     27:   /*
     28:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     29:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     30:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     31:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     32:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     33:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     34:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     35:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     36:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     37:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000); */
     38:   { int j;
     39:     for (j = 0; j<10; j++)
     40:       for (i=0; i<8000000; i++) B[i] = A[i];}

     42:   PetscTime(&y);
     43:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     44:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     45:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     46:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     47:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     48:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     49:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     50:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     51:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     52:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     53:   PetscTime(&z);

     55:   fprintf(stdout,"%s : \n","PetscMemcpy");
     56:   fprintf(stdout,"    %-15s : %e MB/s\n","Bandwidth",10.0*8*8/(y-x));
     57:   fprintf(stdout,"    %-15s : %e sec\n","Latency",(z-y)/10.0);
     58:   fprintf(stdout,"    %-15s : %e sec\n","Per PetscScalar",(2*y-x-z)/8000000.0);

     60:   PetscFree(A);
     61:   PetscFree(B);
     62:   PetscFinalize();
     63:   return(0);
     64: }