Hi all
I am very new to PETSc. I just learnt its class structure and I just understood
that the interface Vec has been reimplemented with the class VecCUSP that is
able to support GPU. My question is: if I have a simple code that allocates a
vector and sets it with the database options, if I specify -vec_type seqcusp
then this vector is allocated AND computed on the GPU?
Because I compared the execution time of the same algorithm with the database
options -vec_type seq and -vec_type seqcusp: these two times are very close.
This is the code: I'm just trying to compute how long does it take to execute
the function VecScale:
#include <petscvec.h>
#include <string.h>
#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **argv)
{
? Vec ? ? ? ? ? ?x;
? PetscInt ? ? ? n;
? PetscErrorCode ierr;
? PetscBool exists;
? PetscLogDouble ?t1,t2;
? PetscInt a=10;
? ierr = PetscInitialize(&argc,&argv,(char*)0,help);CHKERRQ(ierr);?
? ierr = PetscOptionsGetInt(PETSC_NULL,"-size",&n,&exists); CHKERRQ(ierr);
? ierr = VecCreate(PETSC_COMM_SELF,&x);CHKERRQ(ierr);
? ierr = VecSetSizes(x,PETSC_DECIDE,n);CHKERRQ(ierr);
? ierr = VecSetFromOptions(x);CHKERRQ(ierr);
? ierr = VecSetRandom(x, PETSC_NULL); CHKERRQ(ierr);
? PetscGetTime(&t1);
? ierr = VecScale(x,a); CHKERRQ(ierr);
? PetscGetTime(&t2);
? ierr = PetscPrintf(PETSC_COMM_WORLD, "%2.5f\n",(t2-t1));
? ierr = VecDestroy(&x);CHKERRQ(ierr);
? ierr = PetscFinalize();
? return 0;
}
I use a ?vector of about 500000 numbers. With the database option -vec_type
seqcusp , the method VecScale should call the method?VecScale_SeqCUSP, right?
Am I wrong? Should I do it expressly?
Anyway with the option -vec_type seq , the method VecScale takes?0.05681
seconds,?
with the option -vec_type seqcusp,??the method VecScale takes?0.04242 seconds.
Is this speed up sufficient and realistic?
thanks
Olga
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