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LIBOPENCL(7) 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 merely 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.
Each 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 looked for into the standard dynamic
library loader paths.
ENVIRONMENT
Some environment variables can be used modify the default behavior of libOpenCL.
OPENCL_VENDOR_PATH
This variable allows one to modify the default /etc/OpenCL/vendors path. It is
compatible with some other ICD loaders (but not all of them, as the variable is not
part of the standard). Note that $OCL_ICD_VENDORS (see below) is used in priority if
defined and not empty.
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 slashes into $OCL_ICD_VENDORS, libOpenCL.so will first try to use
/etc/OpenCL/vendors/$OCL_ICD_VENDORS (or $OPENCL_VENDOR_PATH/$OCL_ICD_VENDORS if
OPENCL_VENDOR_PATH is defined). If this fail or if there are shashes, 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_LAYERS
This variable allows one to specify a colon separated list of layers to load,
specifying their path. This support is experimental.
OCL_ICD_ASSUME_ICD_EXTENSION
If set to an non-empty value, contrary the Khronos specification, the loader will not
check that the loaded ICDs declare the cl_khr_icd extension. It will also use the
clGetPlatformInfo from the dispatch table if no such function is globally available.
You may need to define this environment variable if you are using not (fully)
compliant ICD, or if you are using the Intel ICD together with optirun(1). In the
latter case, a bug into the Intel ICD will make the application crash.
If set to the debug value, some additional messages will be printed in debug mode (see
OCL_ICD_DEBUG below).
OCL_ICD_PLATFORM_SORT
Allows one to choose the way platforms are sorted when presented to programs through
clGetPlatformIDs(3). Current provided algorithms are:
o 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.
o none: no sort is done and the order can change at each run.
OCL_ICD_DEFAULT_PLATFORM
Number of the platform to choose as default platform. Note that using this environment
variable without ensuring the use of 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:
o 1: warnings (enabled by default if debug support is present and OCL_ICD_DEBUG is
not set)
o 2: informative messages
o 4: entering/exiting for some OpenCL functions
o 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 AT ens-lyon.org>
Author.
2015-06-08 LIBOPENCL(7)
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