On Thu, Dec 22, 2016 at 7:07 AM, Florian Lindner <[email protected]> wrote:
> Hello, > > what is the best / most efficient way to compute: > > y = y - A * b > http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatMultAdd.html Matt > with vectors b, y and matrix A: > > * VecAXPY: I need to compute A*b first > > MatMult(A, b, r); > VecAXPY(y, -1, r); > > * VecWAXPY: Same case, but I don't reuse y > > MatMult(A, b, r); > VecWAXPY(w, -1, r, y); > > * VecAYPX: Don't work, because I need to multiply r = A*b with -1 > > Is there anything else I have overseen, or should I just go with VecAXPY? > > Best, > Florian > -- 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
