.. Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
Spack Project Developers. See the top-level COPYRIGHT file for details.
SPDX-License-Identifier: (Apache-2.0 OR MIT)
.. _cudapackage:
----
Cuda
----
Different from other packages, ``CudaPackage`` does not represent a build system.
Instead its goal is to simplify and unify usage of ``CUDA`` in other packages by providing a `mixin-class <https://en.wikipedia.org/wiki/Mixin>`_.
You can find source for the package at
`<https://github.com/spack/spack/blob/develop/lib/spack/spack/build_systems/cuda.py>`__.
^^^^^^^^
Variants
^^^^^^^^
This package provides the following variants:
* **cuda**
This variant is used to enable/disable building with ``CUDA``. The default
is disabled (or ``False``).
* **cuda_arch**
This variant supports the optional specification of one or multiple architectures.
Valid values are maintained in the ``cuda_arch_values`` property and
are the numeric character equivalent of the compute capability version
(e.g., '10' for version 1.0). Each provided value affects associated
``CUDA`` dependencies and compiler conflicts.
The variant builds both PTX code for the _virtual_ architecture
(e.g. ``compute_10``) and binary code for the _real_ architecture (e.g. ``sm_10``).
GPUs and their compute capability versions are listed at
https://developer.nvidia.com/cuda-gpus .
^^^^^^^^^
Conflicts
^^^^^^^^^
Conflicts are used to prevent builds with known bugs or issues. While
base ``CUDA`` conflicts have been included with this package, you may
want to add more for your software.
For example, if your package requires ``cuda_arch`` to be specified when
``cuda`` is enabled, you can add the following conflict to your package
to terminate such build attempts with a suitable message:
.. code-block:: python
conflicts("cuda_arch=none", when="+cuda",
msg="CUDA architecture is required")
Similarly, if your software does not support all versions of the property,
you could add ``conflicts`` to your package for those versions. For example,
suppose your software does not work with CUDA compute capability versions
prior to SM 5.0 (``50``). You can add the following code to display a
custom message should a user attempt such a build:
.. code-block:: python
unsupported_cuda_archs = [
"10", "11", "12", "13",
"20", "21",
"30", "32", "35", "37"
]
for value in unsupported_cuda_archs:
conflicts(f"cuda_arch={value}", when="+cuda",
msg=f"CUDA architecture {value} is not supported")
^^^^^^^
Methods
^^^^^^^
This package provides one custom helper method, which is used to build
standard CUDA compiler flags.
**cuda_flags**
This built-in static method returns a list of command line flags
for the chosen ``cuda_arch`` value(s). The flags are intended to
be passed to the CUDA compiler driver (i.e., ``nvcc``).
This method must be explicitly called when you are creating the
arguments for your build in order to use the values.
^^^^^
Usage
^^^^^
This helper package can be added to your package by adding it as a base
class of your package. For example, you can add it to your
:ref:`CMakePackage <cmakepackage>`-based package as follows:
.. code-block:: python
:emphasize-lines: 1,7-16
class MyCudaPackage(CMakePackage, CudaPackage):
...
def cmake_args(self):
spec = self.spec
args = []
...
if spec.satisfies("+cuda"):
# Set up the cuda macros needed by the build
args.append("-DWITH_CUDA=ON")
cuda_arch_list = spec.variants["cuda_arch"].value
cuda_arch = cuda_arch_list[0]
if cuda_arch != "none":
args.append(f"-DCUDA_FLAGS=-arch=sm_{cuda_arch}")
else:
# Ensure build with cuda is disabled
args.append("-DWITH_CUDA=OFF")
...
return args
assuming only the ``WITH_CUDA`` and ``CUDA_FLAGS`` flags are required.
You will need to customize options as needed for your build.
This example also illustrates how to check for the ``cuda`` variant using
``self.spec`` and how to retrieve the ``cuda_arch`` variant's value, which
is a list, using ``self.spec.variants["cuda_arch"].value``.
With over 70 packages using ``CudaPackage`` as of January 2021 there are
lots of examples to choose from to get more ideas for using this package.
