This is either a bug in PETSc or some misunderstanding. You certainly should
not have to call VecSet() on y first. Can you send (or point to) us a code that
demonstrates the problem so we can debug?
Barry
> On Sep 11, 2017, at 4:22 PM, Xiangdong wrote:
>
> Hello everyone,
>
> I have a b
Hello everyone,
I have a block matrix B and vec x, and need to compute y=Bx many times. I
found that each time before I call MatMult(B,x,y,ierr), I need to call
VecSet(y,0.0,ierr). Otherwise, the result y is not correct (sometimes, but
not always). I have this puzzle even if x and y are created by
