[petsc-users] MatCreate performance

[Jed Brown]

This is very unusual.  MatCreate() does no work, merely dup'ing a
communicator (or referencing an inner communicator if this is not the
first PetscObject on the provided communicator).  What size matrices are
you working with?  Can you send some performance data and (if feasible)
a reproducer?

Ale Foggia via petsc-users <petsc-users at mcs.anl.gov> writes:

> Hello all,
>
> I have a problem with the scaling of the MatCreate() function. I wrote a
> code to diagonalize sparse matrices and I'm running it in parallel. I've
> observed a very bad speedup of the code and it's given by the MatCreate
> part of it: for a fixed matrix size, when I increase the number of
> processes the time taken by the function also increases. I wanted to know
> if you expect this behavior or if maybe there's something wrong with my
> code. When I go to (what I consider) very big matrix sizes, and depending
> on the number of mpi processes, in some cases, MatCreate takes more time
> than the time the solver takes to solve the system for one eigenvalue or
> the time it takes to set up the values.
>
> Ale