---
name: "futhark-cuda"
section: "1"
platform: "linux"
package: "futhark"
version: "0.25.27-1+b1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/futhark-cuda"
---

# futhark-cuda(1)

compile Futhark to CUDA

## NAME

futhark-cuda - compile Futhark to 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

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*. The **-t** option behaves as with *futhark-opencl*.

The following additional options are accepted.

- **-h, --help**

  Print help text to standard output and exit.

- **--default-thread-block-size=***INT*

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

- **--default-num-thread-blocks=***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.

## 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
```

At runtime the generated program must be able to find the CUDA installation directory, which is normally located at **/usr/local/cuda**.  If you have CUDA installed elsewhere, set any of the **CUDA\_HOME**, **CUDA\_ROOT**, or **CUDA\_PATH** environment variables to the proper directory.

## SEE ALSO

*futhark-opencl*

## COPYRIGHT

2013-2020, DIKU, University of Copenhagen