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Name Strings
Timothy Lottes (timothy.lottes 'at'
Timothy Lottes, AMD
Graham Sellers, AMD
Eric Werness, NVIDIA
Daniel Koch, NVIDIA
Copyright (c) 2015 The Khronos Group Inc. Copyright terms at
Specification Update Policy
Khronos-approved extension specifications are updated in response to
issues and bugs prioritized by the Khronos OpenGL Working Group. For
extensions which have been promoted to a core Specification, fixes will
first appear in the latest version of that core Specification, and will
eventually be backported to the extension document. This policy is
described in more detail at
Complete. Approved by the ARB on June 26, 2015.
Ratified by the Khronos Board of Promoters on August 7, 2015.
Last Modified Date: 2017-04-24
Revision: 7
ARB Extension #179
This extension is written against OpenGL 4.5 (CoreProfile) dated
May 28 2015.
Compiling GLSL into implementation-specific code can be a time consuming
process, so a GL implementation may wish to perform the compilation in a
separate CPU thread. This extension provides a mechanism for the application
to provide a hint to limit the number of threads it wants to be used to
compile shaders, as well as a query to determine if the compilation process
is complete.
New Procedures and Functions
void MaxShaderCompilerThreadsARB(uint count);
New Tokens
Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
GetInteger64v, GetFloatv, and GetDoublev:
Accepted as part of the <pname> parameter to GetShaderiv and
accepted as part of the <pname> parameter to GetProgramiv:
IP Status
Additions to Chapter 7 "Programs and Shaders",
Append to the end of 7.1 "Shader Objects",
Applications may use the following to hint to the driver the maximum
number background threads it would like to be used in the process of
compiling shaders or linking programs,
void MaxShaderCompilerThreadsARB(uint count);
where <count> is the number of background threads. A <count> of zero
specifies a request for no parallel compiling or linking and a <count> of
0xFFFFFFFF requests an implementation-specific maximum.
An implementation may combine the maximum compiler thread request from
multiple contexts in a share group in an implementation-specific way.
An application can query the current MaxShaderCompilerThreadsARB <count>
by calling GetIntegerv with <pname> set to MAX_SHADER_COMPILER_THREADS_ARB,
which returns the value of the current state (Table 23.51).
Add to 7.13 "Shader, Program, and Program Pipeline Queries" under the
descriptions for "pname" for "GetShaderiv",
If <pname> is COMPLETION_STATUS_ARB, TRUE is returned if the shader
compilation has completed, FALSE otherwise.
Add to 7.13 "Shader, Program, and Program Pipeline Queries" under the
descriptions for "pname" for "GetProgramiv",
If <pname> is COMPLETION_STATUS_ARB, TRUE is returned if the program
linking has completed, FALSE otherwise.
New State
Add to Table 23.51: Hints
Get Value Type Get Command Initial Value Description Sec
------------------------------- ---- ------------ ------------- -------------------- ----
MAX_SHADER_COMPILER_THREADS_ARB Z+ GetIntegerv 0xFFFFFFFF Max compile threads 7.13
Add to Table 23.32: Program Object State
Get Value Type Get Command Initial Value Description Sec
--------------------- ---- ------------ ------------- -------------------- ----
COMPLETION_STATUS_ARB B GetProgramiv TRUE Program linking has 7.13
Add to Table 23.30: Shader Object State
Get Value Type Get Command Initial Value Description Sec
--------------------- ---- ------------ ------------- -------------------- ----
COMPLETION_STATUS_ARB B GetShaderiv TRUE Shader compilation 7.13
has completed
1) Where should the hint state be stored?
UNRESOLVED: Each context has its own value which may be specified and
queried, but an implementation may choose to combine the hints from multiple
contexts in an implmentation-specific manner. There isn't really any
precedent for per-share group state.
2) Can we make the requirements more strict?
RESOLVED: We could, but making sure all of the error behavior is correct and
fully specified would likely take more time than we have. This spec allows
an application to clearly request its intent even if there aren't guarantees
that the implementation will exactly obey the request.
3) Does glGetIntegerv(MAX_SHADER_COMPILER_THREADS_ARB) just return the
value set by MaxShaderCompilerThreadsARB? Or, if the state is 0xFFFFFFFF
("do something implementation specific"), does it return the number of
threads the implementation has actually chosen to use?
RESOLVED: As with other state queries, this returns the value that was last
set, or if no value was set by the application it returns the default state
value (0xFFFFFFFF).
Revision History
Rev Date Author Changes
--- ---------- -------- ---------------------------------------------
1 2015-03-22 tlottes Initial revision
2 2015-03-23 tlottes Added way to get MAX_SHADER_COMPILER_THREADS
3 2015-04-20 tlottes Updated tokens and functions
4 2015-06-18 tlottes Added New State, noted per context, issues
5 2016-06-23 ewerness Clarify the spec is a hint, other language fixes
6 2015-09-01 pdaniell Fix the functions that can be used to query
7 2017-04-24 dgkoch Spec clarifications, add issue 3.