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RESOURCE_GROUPS
---------------

Specify resources required by a test, grouped in a way that is meaningful to
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the test.  See :ref:`resource allocation <ctest-resource-allocation>`
for more information on how this property integrates into the CTest resource
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allocation feature.

The ``RESOURCE_GROUPS`` property is a :ref:`semicolon-separated list <CMake
Language Lists>` of group descriptions. Each entry consists of an optional
number of groups using the description followed by a series of resource
requirements for those groups. These requirements (and the number of groups)
are separated by commas. The resource requirements consist of the name of a
resource type, followed by a colon, followed by an unsigned integer
specifying the number of slots required on one resource of the given type.

The ``RESOURCE_GROUPS`` property tells CTest what resources a test expects
to use grouped in a way meaningful to the test.  The test itself must read
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the :ref:`environment variables <ctest-resource-environment-variables>` to
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determine which resources have been allocated to each group.  For example,
each group may correspond to a process the test will spawn when executed.

Consider the following example:

.. code-block:: cmake

  add_test(NAME MyTest COMMAND MyExe)
  set_property(TEST MyTest PROPERTY RESOURCE_GROUPS
    "2,gpus:2"
    "gpus:4,crypto_chips:2")

In this example, there are two group descriptions (implicitly separated by a
semicolon.) The content of the first description is ``2,gpus:2``. This
description specifies 2 groups, each of which requires 2 slots from a single
GPU. The content of the second description is ``gpus:4,crypto_chips:2``. This
description does not specify a group count, so a default of 1 is assumed.
This single group requires 4 slots from a single GPU and 2 slots from a
single cryptography chip. In total, 3 resource groups are specified for this
test, each with its own unique requirements.

When CTest sets the :ref:`environment variables
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<ctest-resource-environment-variables>` for a test, it assigns a group number
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based on the group description, starting at 0 on the left and the number of
groups minus 1 on the right. For example, in the example above, the two
groups in the first description would have IDs of 0 and 1, and the single
group in the second description would have an ID of 2.

Both the ``RESOURCE_GROUPS`` and :prop_test:`RESOURCE_LOCK` properties serve
similar purposes, but they are distinct and orthogonal. Resources specified by
``RESOURCE_GROUPS`` do not affect :prop_test:`RESOURCE_LOCK`, and vice versa.
Whereas :prop_test:`RESOURCE_LOCK` is a simpler property that is used for
locking one global resource, ``RESOURCE_GROUPS`` is a more advanced property
that allows multiple tests to simultaneously use multiple resources of the
same type, specifying their requirements in a fine-grained manner.