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.
- --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 tofoo
.- --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 formNAME=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