"Alletto, John M" <[email protected]> writes:

All,

I have a 64 bit linux machine with 256 GByte of memory and 30 processors. I am solving Laplace equations and the current solver I am using is taking every bit of memory I have available.

What is the current problem size that's filling your memory? How regular is the domain and coefficients? Barry's suggestion won't necessarily reduce memory usage, but it does tend to be fast and easy. How much memory is used by the solver versus other parts of your application? Is the current configuration realistic? It's not worth minimizing solver memory usage if it's going to be a small part of the total application, for example. If you have simple geometry, smooth coefficients, and a standard discretization, a matrix-free full multigrid can solve the problem using about 50 bytes of memory per DOF at a cost of around 5 times as much as a residual evaluation. But many applications don't benefit from such a refined solver.