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:

           •   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 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:

           •   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.

                                            2015-06-08                               LIBOPENCL(7)