libOpenCL (7)

Leading comments

    Title: libOpenCL
   Author: Vincent Danjean <Vincent.Danjean@ens-lyon.org>
Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
     Date: 2015-06-08
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 Language: English

(The comments found at the beginning of the groff file "man7/libOpenCL.7".)

NAME

libOpenCL, libOpenCL.so - OCL-ICD implementation of OpenCL ICD loader

DESCRIPTION

libOpenCL.so is the library linked by OpenCL programs. It does not contains any OpenCL implementation itself, but merly act as a dispatcher to real OpenCL implementations provided as OpenCL Installable Client Driver (ICD). An ICD loader should be able to load ICDs provided by any vendors.

According to OpenCL specifications from Khronos (see [Khronos]), the ICD Loader looks for files into /etc/OpenCL/vendors/ directory and, for each file whose name ends with .icd, the ICD Loader loads with dlopen(3) the shared library whose name is on the first line of the .icd file.

Shared library name in ".icd" files can have its path, or it can be a plain filename. In the latter case, the ICD shared library will be look for into the standard dynamic loader paths.

ENVIRONMENT

Some environment variables can be used modify the default behavior of libOpenCL.

OCL_ICD_VENDORS

This variable allows one to change the way ICD are searched on the system. Several cases are considered:

1. if $OCL_ICD_VENDORS is a directory path, then this path replaces the "/etc/OpenCL/vendors" path in the standard behavior: the loader will use the .icd files in this directory;

2. else, if $OCL_ICD_VENDORS ends with .icd, libOpenCL.so will only load the ICD whose shared library name is wrote into the specified ".icd" file;
If there is no slash into $OCL_ICD_VENDORS, libOpenCL.so will first try to use /etc/OpenCL/vendors/$OCL_ICD_VENDORS. If this fail, it uses $OCL_ICD_VENDORS (as a relative or absolute file name path).

3. else libOpenCL.so will try to load $OCL_ICD_VENDORS as the ICD shared library itself (i.e. to load it directly with dlopen(3)).

OCL_ICD_ASSUME_ICD_EXTENSION

If set, contrary the Khronos specification, the loader will not check that the loaded ICDs declare the cl_khr_icd extension. You may need to define this environment variable if you are using the Intel ICD together with optirun(1). Else, a bug into the Intel ICD will make the application crash.

OCL_ICD_PLATFORM_SORT

Allows one to choose the way platforms are sorted when presented to programs through clGetPlatformIDs(3). Current provided algorithms are:

* devices: first, list platforms that support most GPU, then most CPU then most accelerators. If OCL_ICD_PLATFORM_SORT is not set or set to an unknown value, this algorithm is used.

* none: no sort is done and the order can very at each run.

OCL_ICD_DEFAULT_PLATFORM

Number of the platform to choose as defaut platform. Note that using this environment variable without specifying a sort algorithm for platforms is not really useful.

OCL_ICD_DEBUG

If ocl-icd has been compiled with debug support, you can set this environment variable to a value where each bit display some kind of informations. Defined values are:

* 1: warnings (enabled by default if debug support is present and OCL_ICD_DEBUG is not set)

* 2: informative messages

* 4: entering/exiting for some OpenCL functions

* 8: dump of the internal structure of loaded ICDs

OCL_ICD_DEBUG is mainly useful for ocl-icd development itself and/or for ICD development.

SEE ALSO

Khronos OpenCL registry website

AUTHOR

Vincent Danjean <Vincent.Danjean@ens-lyon.org>

Author.