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.\"     Title: barrier
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 01/03/2018
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
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.TH "BARRIER" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
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.SH "NAME"
barrier \- synchronize execution of multiple shader invocations
.SH "DECLARATION"
.HP \w'void\ barrier('u
.BI "void barrier(void);"
.SH "DESCRIPTION"
.PP
\fIAvailable only in the Tessellation Control and Compute Shaders\fR,
\fBbarrier\fR
provides a partially defined order of execution between shader invocations\&. For any given static instance of
\fBbarrier\fR, in a tessellation control shader, all invocations for a single input patch must enter it before any will be allowed to continue beyond it\&. For any given static instance of
\fBbarrier\fR
in a compute shader, all invocations within a single work group must enter it before any are allowed to continue beyond it\&. This ensures that values written by one invocation prior to a given static instance of
\fBbarrier\fR
can be safely read by other invocations after their call to the same static instance of
\fBbarrier\fR\&. Because invocations may execute in undefined order between these
\fBbarrier\fR
calls, the values of a per\-vertex or per\-patch output variable, or any shared variable will be undefined in a number of cases\&.
.PP
\fBbarrier\fR
may only be placed inside the function
main()
of the tessellation control shader, but may be placed anywhere in a compute shader\&. Calls to
\fBbarrier\fR
may not be placed within any control flow\&. Barriers are also disallowed after a return statement in the function
main()\&.
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Shading Language Version\fR
T}
T{
\fBFunction Name\fR
T}:T{
\fB1\&.10\fR
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\fB1\&.20\fR
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\fB1\&.30\fR
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\fB1\&.40\fR
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\fB1\&.50\fR
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\fB3\&.30\fR
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\fB4\&.00\fR
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\fB4\&.10\fR
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\fB4\&.20\fR
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\fB4\&.30\fR
T}:T{
\fB4\&.40\fR
T}:T{
\fB4\&.50\fR
T}
.T&
l c c c c c c c c c c c c.
T{
barrier
T}:T{
\-
T}:T{
\-
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\-
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\-
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\-
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\-
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✔
T}:T{
✔
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✔
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✔
T}:T{
✔
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✔
T}
.TE
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.SH "COPYRIGHT"
.PP
Copyright
\(co
2011\-2014 Khronos Group\&. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1\&.0, 8 June 1999\&.
\m[blue]\fBhttp://opencontent\&.org/openpub/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 2011-2014 Khronos Group
.br