Geoffrey Irving <[email protected]> writes: > Here are results with -ksp_monitor_true_residual -pc_type none: > > http://naml.us/random/laplace-rtol.txt # with -ksp_rtol 1e-5 > http://naml.us/random/laplace-atol.txt # with -ksp_atol 1e-5
Looks like the preconditioner is singular. > Both versions converge in 3 iterations for the first SNES iteration, > but the relative one starts to churn after that since the residual > starts very small. The true residual goes down to 4/3 and stagnates. > Is there a convenient way to print out the RHS to see whether it has a > component in the nullspace (which seems likely given the true residual > stagnation)? -snes_monitor_residual will plot the solution. (This option should be upgraded to support arbitrary output formats.) You can also call VecView from your residual function. > I suppose I already do print the result of SNESComputeFunction on the > zero vec, which is > > RHS = [ 6.66666667e-01 1.33333333e+00 6.66666667e-01 > 1.11022302e-16] Looks like you need to project out the null space.
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