[petsc-dev] accuracy of solutions PETSc returns

Barry Smith bsmith at mcs.anl.gov
Thu Apr 22 15:59:18 CDT 2010

   The petsc-maint request titled "Question on setting rtol in KSP"  
points to a HUGE deficiency in PETSc.

   When PETSc returns an answer to a linear or nonlinear solver it  
returns no useful information about how accurate that solution is. In  
any other field beside numerical computing this would be considered  
disgraceful.  We should fix this for KSP and SNES and also make sure  
that ALL the TS's allow proper error control (as some of them already  


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