Fix: CUDA Host-Side -O3 with CMake

`-O3` was only set for CUDA if we ran CMake at least twice. This was
an intialization logic bug and should be set from the beginning, but
we initialized CUDA too late / applied the transform too early.

We now change the default build type to `Release` to avoid changing
defaults and avoid further surprises.

We will add optional `-g` for optimized builds again on a later PR.

CMakeLists.txt

@@ -67,7 +67,7 @@ endif()
 option(HiPACE_amrex_internal "Download & build AMReX" ON)
 
 # change the default build type to RelWithDebInfo (or Release) instead of Debug
-set_default_build_type("RelWithDebInfo")
+set_default_build_type("Release")
 
 # this defined the variable BUILD_TESTING which is ON by default
 include(CTest)

cmake/HiPACEFunctions.cmake

@@ -72,13 +72,6 @@ macro(set_default_build_type default_build_type)
             set_property(CACHE CMAKE_BUILD_TYPE
                     PROPERTY STRINGS ${CMAKE_CONFIGURATION_TYPES})
         endif()
-
-        # RelWithDebInfo uses -O2 which is sub-ideal for how it is intended to be used
-        #   https://gitlab.kitware.com/cmake/cmake/-/merge_requests/591
-        list(TRANSFORM CMAKE_C_FLAGS_RELWITHDEBINFO REPLACE "-O2" "-O3")
-        list(TRANSFORM CMAKE_CXX_FLAGS_RELWITHDEBINFO REPLACE "-O2" "-O3")
-        # FIXME: due to the "AMReX inits CUDA first" logic we will first see this with -O2 in output
-        list(TRANSFORM CMAKE_CUDA_FLAGS_RELWITHDEBINFO REPLACE "-O2" "-O3")
     endif()
 endmacro()
 

docs/source/building/building.rst

@@ -156,7 +156,7 @@ or by providing arguments to the CMake call
 =============================  ========================================  =====================================================
  CMake Option                  Default & Values                          Description
 -----------------------------  ----------------------------------------  -----------------------------------------------------
- ``CMAKE_BUILD_TYPE``          **RelWithDebInfo**/Release/Debug          Type of build, symbols & optimizations
+ ``CMAKE_BUILD_TYPE``          RelWithDebInfo/**Release**/Debug          Type of build, symbols & optimizations
  ``HiPACE_COMPUTE``            **NOACC**/CUDA/SYCL/HIP/OMP               On-node, accelerated computing backend
  ``HiPACE_MPI``                **ON**/OFF                                Multi-node support (message-passing)
  ``HiPACE_PRECISION``          SINGLE/**DOUBLE**                         Floating point precision (single/double)