[petsc-users] Product of matrix row times a vector

[Jeremy Theler]

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