Hey again,

Thanks for your info. To set the record straight, turning back on the smoothing option improved the solving time, not decrease it, my bad. The simple (didr.cpp) IDR performance (not converging) that I mentioned, was actually due to not having smoothing on. So in my case, smoothing has GREAT beneficial impact on my convergence behavior. But, yes smoothing=0/1 should be handled, imo, by opts not at compilation; omega's value impact is trivial compared to the former, plus my investigation showed really no effect, since its only a starting value I suppose, right?

Regarding your question, I am into the field of CFD, so my matrices are mainly products of Navier-Stokes equations descretization with finite elements, k-epsilon turbulence etc. Ofc, they are sparse matrices, and with different characteristics per generating equation. I am exploring MAGMA solver/preconditioner performance, especially your _merge implementations on various matrices/sizes. So far they seem very promising :) There are some sparse solvers I never heard about, though I am nowhere near a LA expert, like bombardment etc, so I might give those a try too!