[petsc-users] MatSolve in CG

[De Groof, Vincent Frans Maria]

Dear all,


I am writing a few variations on the PCG algorithm. Starting with my own PCG implementation, I noticed that my routine is quite a bit slower (~20%). I think I tracked it down to the MatSolve calls in PCApply. I am using BDDC as the preconditioner.

In the Petsc PCG function, each PCApply calls the MatSolve 3 times. It also calls MatSolve once somewhere between calling KSPSolve and KSPSolve_CG (KSP_SetUp has been called before). So MatSolve is called 1+3*(# iterations) per KSPSolve. In my own PCG variation, the initial MatSolve is not called. But MatSolve is called 4 times in each iteration, so in total 4*(# iterations).

Where does this MatSolve in between KSPSolve and KSPSolve_CG come from? And how can I make my function use less MatSolve's?


I hope that I explained the problem clearly, and maybe this is a very trivial question.


kind regards,
Vincent
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20141110/fabc347d/attachment-0001.html>