futhark-cuda

SYNOPSIS

futhark cuda [options…] <program.fut>

DESCRIPTION

futhark cuda translates a Futhark program to C code invoking CUDA 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 cuda uses -lcuda -lcudart -lnvrtc to link. If using --library, you will need to do the same when linking the final binary.

The generated CUDA code can be called from multiple CPU threads, as it brackets every API operation with cuCtxPushCurrent() and cuCtxPopCurrent().

OPTIONS

-h

Print help text to standard output and exit.

--entry NAME

Treat the specified top-level function as an entry point.

--library

Generate a library instead of an executable. Appends .c/.h to the name indicated by the -o option to determine output file names.

-o outfile

Where to write the result. If the source program is named foo.fut, this defaults to foo.

--safe

Ignore unsafe in program and perform safety checks unconditionally.

-v verbose

Enable debugging output. If compilation fails due to a compiler error, the result of the last successful compiler step will be printed to standard error.

-V

Print version information on standard output and exit.

-W

Do not print any warnings.

--Werror

Treat warnings as errors.

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. The -t option behaves as with futhark-opencl. For commonality, the options use OpenCL nomenclature (“group” instead of “thread block”).

The following additional options are accepted.

-h, --help

Print help text to standard output and exit.

--default-group-size=INT

The default size of thread blocks that are launched. Capped to the hardware limit if necessary.

--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).

--dump-cuda=FILE

Don’t run the program, but instead dump the embedded CUDA kernels to the indicated file. Useful if you want to see what is actually being executed.

--dump-ptx=FILE

Don’t run the program, but instead dump the PTX-compiled version of the embedded kernels to the indicated file.

--load-cuda=FILE

Instead of using the embedded CUDA kernels, load them from the indicated file.

--load-ptx=FILE

Load PTX code from the indicated file.

--nvrtc-option=OPT

Add an additional build option to the string passed to NVRTC. Refer to the CUDA documentation for which options are supported. Be careful - some options can easily result in invalid results.

--print-sizes

Print all sizes that can be set with -size or --tuning.

--size=ASSIGNMENT

Set a configurable run-time parameter to the given value. ASSIGNMENT must be of the form NAME=INT Use --print-sizes to see which names are available.

--tuning=FILE

Read size=value assignments from the given file.

ENVIRONMENT

If run without --library, futhark cuda will invoke a C compiler to compile the generated C program into a binary. This only works if the C compiler can find the necessary CUDA libraries. On most systems, CUDA is installed in /usr/local/cuda, which is usually not part of the default compiler search path. You may need to set the following environment variables before running futhark cuda:

LIBRARY_PATH=/usr/local/cuda/lib64
LD_LIBRARY_PATH=/usr/local/cuda/lib64/
CPATH=/usr/local/cuda/include

SEE ALSO

futhark-opencl