[petsc-users] Using GAMG to speed up solving of Poisson eqn

[Mark F. Adams]

>> 
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>> -poisson_ksp_monitor -poisson_pc_gamg_verbose

"verbose" takes an integer so give it > 0.  0 is the default.  But getting a stack trace in the debugger is much better.  

Does this code run correctly with simple default (ILU) preconditioning?  As I recall you were getting floating point exceptions when computing the extreme eigen values.  Try running with ILU and add -poisson_ksp_monitor_singular_value to see if this a general problem or a GAMG specific problem.