Poisson solvers residual visualisation

visualisation of the residual channel after solving poisson equation on 256x256 domain with irregular BCs up to 10^-3, red corresponds to the positive r values and green -- to negativities respectivetly. On the top level corner the original problem is shown, where red corresponds to neumann and blue to dirichlet BC. JI = jacobi iterator SOR = successive overrelaxation scheme CG = conjugate gradient MICPCG = modified incomplete cholesky preconditioned CG (see Robert Bridson's fluid course notes on explanation in what exactly that modification is) MG = multigrid Theoretically, the fastest method to solve there problems is a multigrid preconditioned CG (MGPCG) much like that one i used in my own fluid solver http://blackcore.technology/softimage_efx. However, MGs family tends to diverge sometimes in the presence of irregular BCso additional care around nonfluid voxels must be taken.