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)).

       OPENCL_LAYERS
           This variable allows one to specify a colon separated list of layers to load, specifying their path.

       OPENCL_LAYER_PATH
           This variable allows one to override the default system layer search path (/etc/OpenCL/layers).

       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)