#include "petsclog.h" PetscErrorCode PetscLogNestedBegin(void)Logically Collective over PETSC_COMM_WORLD
| -log_view :filename.xml:ascii_xml | - Prints an XML summary of flop and timing information to the file | 
      PetscInitialize(...);
      PetscLogNestedBegin();
       ... code ...
      PetscLogView(viewer);
      PetscFinalize();