1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
<HTML>
<HEAD> <link rel="canonical" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscOmpCtrlBarrier.html" />
<META NAME="GENERATOR" CONTENT="DOCTEXT">
<TITLE>PetscOmpCtrlBarrier</TITLE>
</HEAD>
<BODY BGCOLOR="FFFFFF">
<div id="version" align=right><b>petsc-3.14.5 2021-03-03</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.14.5 v3.14.5 docs/manualpages/Sys/PetscOmpCtrlBarrier.html "><small>Report Typos and Errors</small></a></div>
<A NAME="PetscOmpCtrlBarrier"><H1>PetscOmpCtrlBarrier</H1></A>
Do barrier on MPI ranks in omp_comm contained by the PETSc OMP controller (to let slave ranks free their CPU)
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsys.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../Sys/PetscOmpCtrlBarrier.html#PetscOmpCtrlBarrier">PetscOmpCtrlBarrier</A>(PetscOmpCtrl ctrl)
</PRE>
<H3><FONT COLOR="#CC3333">Input Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ctrl </B></TD><TD>- a PETSc OMP controller
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
this is a pthread barrier on MPI processes. Using MPI_Barrier instead is conceptually correct. But MPI standard does not
require processes blocked by MPI_Barrier free their CPUs to let other processes progress. In practice, to minilize latency,
MPI processes stuck in MPI_Barrier keep polling and do not free CPUs. In contrast, pthread_barrier has this requirement.
<P>
A code using <A HREF="../Sys/PetscOmpCtrlBarrier.html#PetscOmpCtrlBarrier">PetscOmpCtrlBarrier</A>() would be like this,
<P>
if (is_omp_master) {
<A HREF="../Sys/PetscOmpCtrlOmpRegionOnMasterBegin.html#PetscOmpCtrlOmpRegionOnMasterBegin">PetscOmpCtrlOmpRegionOnMasterBegin</A>(ctrl);
Call the library using OpenMP
<A HREF="../Sys/PetscOmpCtrlOmpRegionOnMasterEnd.html#PetscOmpCtrlOmpRegionOnMasterEnd">PetscOmpCtrlOmpRegionOnMasterEnd</A>(ctrl);
}
<A HREF="../Sys/PetscOmpCtrlBarrier.html#PetscOmpCtrlBarrier">PetscOmpCtrlBarrier</A>(ctrl);
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Sys/PetscOmpCtrlOmpRegionOnMasterBegin.html#PetscOmpCtrlOmpRegionOnMasterBegin">PetscOmpCtrlOmpRegionOnMasterBegin</A>(), <A HREF="../Sys/PetscOmpCtrlOmpRegionOnMasterEnd.html#PetscOmpCtrlOmpRegionOnMasterEnd">PetscOmpCtrlOmpRegionOnMasterEnd</A>()
<BR><P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>developer<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/sys/utils/mpishm.c.html#PetscOmpCtrlBarrier">src/sys/utils/mpishm.c</A>
<BR><A HREF="./index.html">Index of all Sys routines</A>
<BR><A HREF="../../index.html">Table of Contents for all manual pages</A>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
</BODY></HTML>
|
