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
