#include <petscsys.h> PetscErrorCode (*PetscErrorPrintf)(const char format[],...);Not Collective
| format | - the usual printf() format string | 
| -error_output_stdout | - cause error messages to be printed to stdout instead of the (default) stderr | |
| -error_output_none | - to turn off all printing of error messages (does not change the way the error is handled.) | 
    PetscErrorPrintf = PetscErrorPrintfNone; to turn off all printing of error messages (does not change the way the
                       error is handled.) and
    PetscErrorPrintf = PetscErrorPrintfDefault; to turn it back on or you can use your own function
Use PETSC_STDERR = FILE* obtained from a file open etc. to have stderr printed to the file. PETSC_STDOUT = FILE* obtained from a file open etc. to have stdout printed to the file.
Use PetscPushErrorHandler() to provide your own error handler that determines what kind of messages to print