[cmake] Use GALARIO_CHECK_CUDA

Interface is a bit more consistent from the user perspective

CMakeLists.txt

@@ -33,9 +33,15 @@ include(LookUp-GreatCMakeCookOff)
 ###
 # the optional packages
 ###
-if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin" AND NOT GALARIO_FORCE_CUDA)
-  message(STATUS "Ignoring cuda on the mac by default. Force searching for cuda with `cmake -DGALARIO_FORCE_CUDA=1`")
-else()
+if(NOT DEFINED GALARIO_CHECK_CUDA)
+  if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+    message(STATUS "Ignoring cuda on the mac by default. Force searching for cuda with `cmake -DGALARIO_CHECK_CUDA=1`")
+    set(GALARIO_CHECK_CUDA 0)
+  else()
+    set(GALARIO_CHECK_CUDA 1)
+  endif()
+endif()
+if(GALARIO_CHECK_CUDA)
   find_package(CUDA)
 endif()
 

docs/install.rst

@@ -277,18 +277,12 @@ CUDA
 `cmake` tests for compilation on the GPU with cuda by default **except on Mac OS**,
 where version conflicts between the NVIDIA compiler and the C++ compiler often lead to problems (see `this issue <https://github.com/mtazzari/galario/issues/30>`_).
 
-To manually turn OFF CUDA compilation, disable the search for the CUDA package:
+To manually enable or disable checking for cuda, do
 
 .. code-block:: bash
 
-    cmake -DCMAKE_DISABLE_FIND_PACKAGE_CUDA=1 ..
-
-On the opposite, to force searching for CUDA, for example on Mac OS, do:
-
-.. code-block:: bash
-
-    cmake -DGALARIO_FORCE_CUDA=1 ..
-
+   cmake -DGALARIO_CHECK_CUDA=0 .. # don't check
+   cmake -DGALARIO_CHECK_CUDA=1 .. # check
 
 Timing
 ~~~~~~
@@ -300,7 +294,6 @@ passing the additional flag:
 
     cmake -DGALARIO_TIMING=1 ..
 
-
 .. _install_details:
 
 Install