petsc-dev 2014-07-25
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PetscSequentialPhaseBegin

Begins a sequential section of code.

Synopsis

#include "petscsys.h"  
PetscErrorCode  PetscSequentialPhaseBegin(MPI_Comm comm,int ng)
Collective on MPI_Comm

Input Parameters

comm - Communicator to sequentialize.
ng - Number in processor group. This many processes are allowed to execute at the same time (usually 1)

Notes

PetscSequentialPhaseBegin() and PetscSequentialPhaseEnd() provide a way to force a section of code to be executed by the processes in rank order. Typically, this is done with
      PetscSequentialPhaseBegin(comm, 1);
      <code to be executed sequentially>
      PetscSequentialPhaseEnd(comm, 1);

Often, the sequential code contains output statements (e.g., printf) to be executed. Note that you may need to flush the I/O buffers before calling PetscSequentialPhaseEnd(). Also, note that some systems do not propagate I/O in any order to the controling terminal (in other words, even if you flush the output, you may not get the data in the order that you want).

See Also

PetscSequentialPhaseEnd()

Level:intermediate
Location:
src/sys/utils/mpiu.c
Index of all Sys routines
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Index of all manual pages