MatGetSubMatrix() and then do the product on the sub matrix then VecSum
Barry > On Jan 30, 2020, at 3:02 PM, Jeremy Theler <jer...@seamplex.com> wrote: > > Sorry if this is basic, but I cannot figure out how to do it in > parallel and I'd rather not say how I do it in single-processor mode > because I would be ashamed. > > Say I have a matrix and I want to multiply a row times a vector to > obtain a scalar. Actually I would like to choose some rows, multiply > each of them by the vector and then add the scalars up. Or, conversely, > sum all the rows colmunwise and then multiply the sum by a vector. > > How can I do this? > > > Regards > -- > jeremy theler > www.seamplex.com > >