Actual source code: PetscMemcpy.c

     2:  #include petsc.h

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

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

     14:   PetscMalloc(8000000*sizeof(PetscScalar),&A);
     15:   PetscMalloc(8000000*sizeof(PetscScalar),&B);

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

     25:   PetscGetTime(&x);
     26:   /*
     27:   PetscMemcpy(A,B,sizeof(PetscScalar)*8000000);
     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:   { int j;
     38:   for (j = 0; j<10; j++) {
     39:     for (i=0; i<8000000; i++) {
     40:       B[i] = A[i];
     41:     }
     42:   }}

     44:   PetscGetTime(&y);
     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:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     54:   PetscMemcpy(A,B,sizeof(PetscScalar)*0);
     55:   PetscGetTime(&z);

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

     62:   PetscFree(A);
     63:   PetscFree(B);
     64:   PetscFinalize();
     65:   return(0);
     66: }