Hi, Matthew Thank you very much for the answer. And I met a new problem. When there some PetscScalar type data operations before the VecWAXPY call, for example
PetscScalar, a,b, c; ..... ..... c=a+b; ierr = VecWAXPY(r, c, Ax, b);CHKERRQ(ierr); , should I add MPI_Barrier call right before VecWAXPY call ? Best regards Cong On Fri, Aug 16, 2013 at 7:56 PM, Matthew Knepley <[email protected]> wrote: > On Fri, Aug 16, 2013 at 2:11 AM, Cong Li <[email protected]> wrote: > >> Hi >> >> I am a rookie to PETSc, and I am wondering about whether I should call >> MPI_Barrier to explicitly synchronize processes between PETSc calls. >> For example, a piece of code like below >> >> ierr = MatMult(A,x,Ax); CHKERRQ(ierr); >> ierr = VecWAXPY(r, neg_one, Ax, b);CHKERRQ(ierr); >> >> Should I add MPI_Barrier inbetween MatMult call and VecWAXPY call ? >> > > No > > Matt > > >> My guess is that it is unnecessary. However, I am not so confident in >> this guess, for I don't have much experience on using PETSc. >> >> Thanks in advance. >> >> Cong Li >> > > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener >
