https://www.mcs.anl.gov/petsc/documentation/faq.html#efficient-assembly
> On Mar 8, 2019, at 9:19 AM, Ale Foggia via petsc-users > <[email protected]> wrote: > > 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
