Edoardo alinovi <[email protected]> writes: > Dear Guys, > > I have quick question for you. Can anyone tell me if MatDiagonalSet needs > also MatAssemblyBegin/MatAssemblyEnd to be called afterwards or not?
It's called internally so you don't have to call again. > Basically, I am trying to compute: sum (a_nb*\phi_nb), where anb are the > off diagonal coeffs of the matrix and phi_nb the corresponding field > values. > > I was thinking to set the matrix diagonal to zero using MatDiagonalSet and > then simply use MatMult(A, x) to accomplish my task. Do we have a better > way in PETSc? Any suggestion in welcome :) An alternative would be to extract the diagonal and subtract off the result of VecPointwiseMult(w, diag, phi).
