NAME

       futhark-opencl - compile Futhark to OpenCL

SYNOPSIS

       futhark opencl [options…] <program.fut>

DESCRIPTION

       futhark opencl translates a Futhark program to C code invoking OpenCL kernels, and either compiles that C
       code  with  a C compiler to an executable binary program, or produces a .h and .c file that can be linked
       with other code. The standard Futhark optimisation pipeline is used.

       futhark opencl uses -lOpenCL to link (-framework OpenCL on macOS).  If using --library, you will need  to
       do the same when linking the final binary.

       The GPU terminology used is derived from CUDA nomenclature (e.g.  “thread block” instead of “workgroup”),
       but OpenCL nomenclature is also supported for compatibility.

OPTIONS

       Accepts the same options as futhark-c.

ENVIRONMENT VARIABLES

       CC
          The C compiler used to compile the program.  Defaults to cc if unset.

       CFLAGS
          Space-separated list of options passed to the C compiler.  Defaults to -O -std=c99 if unset.

EXECUTABLE OPTIONS

       Generated  executables  accept  the same options as those generated by futhark-c.  For the -t option, The
       time taken to perform device setup or teardown, including writing the input or reading the result, is not
       included in the measurement. In particular, this means that timing starts after  all  kernels  have  been
       compiled  and  data has been copied to the device buffers but before setting any kernel arguments. Timing
       stops after the kernels are done running, but before data has been read from the buffers or  the  buffers
       have been released.

       The following additional options are accepted.

       --build-option=OPT
              Add  an  additional  build  option  to the string passed to clBuildProgram().  Refer to the OpenCL
              documentation for which options are supported.  Be careful - some options  can  easily  result  in
              invalid results.

       --default-thread-block-size=INT, --default-group-size=INT
              The default size of thread blocks that are launched. Capped to the hardware limit if necessary.

       --default-num-thread-blocks,--default-num-groups=INT
              The default number of thread blocks that are launched.

       --default-threshold=INT
              The  default  parallelism  threshold  used  for  comparisons  when selecting between code versions
              generated by incremental flattening.  Intuitively, the amount of parallelism  needed  to  saturate
              the GPU.

       --default-tile-size=INT
              The  default tile size used when performing two-dimensional tiling (the workgroup size will be the
              square of the tile size).

       -d,--device=NAME
              Use the first OpenCL device whose name contains the given string.  The special string #k, where  k
              is  an  integer,  can be used to pick the k-th device, numbered from zero.  If used in conjunction
              with -p, only the devices from matching platforms are considered.

       --dump-opencl=FILE
              Don’t run the program, but instead dump the embedded OpenCL program to the indicated file.  Useful
              if you want to see what is actually being executed.

       --dump-opencl-binary=FILE
              Don’t run the program, but instead dump the compiled version of the embedded OpenCL program to the
              indicated file.  On NVIDIA platforms, this will be PTX code.

       --load-opencl=FILE
              Instead of using the embedded OpenCL program, load it from the indicated file.

       --load-opencl-binary=FILE
              Load an OpenCL binary from the indicated file.

       -p,--platform=NAME
              Use the first OpenCL platform whose name contains the given string.  The special string #k,  where
              k is an integer, can be used to pick the k-th platform, numbered from zero.

       --list-devices
              List all OpenCL devices and platforms available on the system.

SEE ALSO

       futhark-test, futhark-cuda, futhark-c

COPYRIGHT

       2013-2020, DIKU, University of Copenhagen

0.25.32                                           Aug 22, 2025                                 FUTHARK-OPENCL(1)