[autodiff] new package for optional dependency of acts (#28028)

var/spack/repos/builtin/packages/acts/package.py

@@ -139,9 +139,9 @@ class Acts(CMakePackage, CudaPackage):
     variant('analysis', default=False, description='Build analysis applications in the examples')
 
     # Build dependencies
-    # FIXME: Use spack's autodiff package once there is one
     # FIXME: Use spack's vecmem package once there is one
     # (https://github.com/acts-project/acts/pull/998)
+    depends_on('autodiff @0.5.11:', when='@1.2: +autodiff')
     depends_on('boost @1.62:1.69 +program_options +test', when='@:0.10.3')
     depends_on('boost @1.71: +filesystem +program_options +test', when='@0.10.4:')
     depends_on('cmake @3.14:', type='build')
@@ -228,8 +228,9 @@ def plugin_cmake_variant(plugin_name, spack_variant):
             cxxstd = spec['root'].variants['cxxstd'].value
             args.append("-DCMAKE_CXX_STANDARD={0}".format(cxxstd))
 
-        # FIXME: Once we can use spack's autodiff package, set
-        #        ACTS_USE_SYSTEM_AUTODIFF too.
+        if spec.satisfies('+autodiff'):
+            args.append("-DACTS_USE_SYSTEM_AUTODIFF=ON")
+
         if spec.satisfies('@0.33: +json'):
             args.append("-DACTS_USE_SYSTEM_NLOHMANN_JSON=ON")
         elif spec.satisfies('@0.14.0: +json'):

var/spack/repos/builtin/packages/autodiff/package.py

@@ -0,0 +1,35 @@
+# Copyright 2013-2021 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)
+
+from spack import *
+
+
+class Autodiff(CMakePackage):
+    """autodiff is automatic differentiation made easier for C++."""
+
+    homepage = "https://autodiff.github.io"
+    url      = "https://github.com/autodiff/autodiff/archive/refs/tags/v0.6.4.tar.gz"
+    list_url = "https://github.com/autodiff/autodiff/releases"
+    git      = "https://github.com/autodiff/autodiff.git"
+
+    maintainers = ['wdconinc', 'HadrienG2']
+
+    version('0.6.4',  sha256='cfe0bb7c0de10979caff9d9bfdad7e6267faea2b8d875027397486b47a7edd75')
+    version('0.5.13', sha256='a73dc571bcaad6b44f74865fed51af375f5a877db44321b5568d94a4358b77a1')
+
+    variant('python', default='False', description='Enable the compilation of the python bindings.')
+    variant('examples', default='False', description='Enable the compilation of the example files.')
+
+    depends_on('cmake@3.0:', type='build')
+    depends_on('eigen')
+    depends_on('py-pybind11', type=('build', 'run'))
+
+    def cmake_args(self):
+        args = [
+            self.define('AUTODIFF_BUILD_TESTS', self.run_tests),
+            self.define_from_variant('AUTODIFF_BUILD_PYTHON', 'python'),
+            self.define_from_variant('AUTODIFF_BUILD_EXAMPLES', 'examples',)
+        ]
+        return args