[petsc-users] Termination criteria for solving linear system

Thomas Witkowski thomas.witkowski at tu-dresden.de
Tue Feb 2 06:05:54 CST 2010

In my computations I use "bicg" preconditioned by "bjacobi" with an 
absolute tolerance of 1^e-8 as termination criteria. After PETSc has 
computed the solution, the code computes the residual. It is usually in 
the magnitude of 1^-13. I'm not really sure what happens here. Is it, 
because PETSc checks the preconditioned residual? If so, is there a way 
to tune the termination criteria to the true residual? I would like to 
save some computational time, since I do not need to solve the system 
with this high precision.



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