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CMake set release flags properly (wrf-model#2138)
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TYPE: bug fix

KEYWORDS: cmake, flags, optimization

SOURCE: internal

DESCRIPTION OF CHANGES:
Problem:
To feed initial flags into the cmake build, a toolchain file is used. 

However, for particular build configurations, namely release and debug,
despite the configuration being "Release" and "Debug", respectively, the
corresponding `CMAKE_<LANG>_FLAGS_<CONFIG>_INIT` has the configuration
name capitalized.

Additionally, these initial flags supplement the starting flags and do
not override any inherited flags that CMake automatically appends. This
can cause issues with certain compilers where subsequent flags that
normally should supersede previously listed options are ignored. As an
example, using nvfortran/pgi the following will cause forced
optimization, which is not viable for some files within WRF :

https://forums.developer.nvidia.com/t/nvfortran-reducing-optimation-level-by-multiple-on-does-not-work/191825

https://forums.developer.nvidia.com/t/how-to-override-pgccs-optimization-flag/136275

Finally, certain files do not have optimization overridden even if it
were to work correctly

Solution:
Ensure correct variable name in toolchain file to provide initial
starting flags, and wipe CMake-injected release flags to avoid
significant deviation from provided optimization flags. Add proper
directory scope to files that need these reduced optimizations.


TESTS CONDUCTED: 
1. Tested with CMake build on Derecho selecting nvhpc/pgi compiler
stanzas

RELEASE NOTE: Override CMake-injected optimization flags in favor of the
flags set by the build system and provided stanza information.
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islas authored Dec 20, 2024
1 parent 4889c3c commit b6542b0
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Showing 3 changed files with 11 additions and 4 deletions.
5 changes: 5 additions & 0 deletions CMakeLists.txt
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,11 @@ if ( DEFINED CMAKE_TOOLCHAIN_FILE )
# include( ${WRF_CONFIG} )
endif()

# Import default flags now, get rid of any imported release flag
# we will handle that ourselves with WRF_FCOPTIM/WRF_FCNOOPT
set( CMAKE_Fortran_FLAGS_RELEASE "" CACHE STRING "" FORCE )
set( CMAKE_C_FLAGS_RELEASE "" CACHE STRING "" FORCE )

# list( APPEND CMAKE_MODULE_PATH )
list( APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/ ${PROJECT_SOURCE_DIR}/cmake/modules )

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8 changes: 4 additions & 4 deletions cmake/template/arch_config.cmake
Original file line number Diff line number Diff line change
Expand Up @@ -15,10 +15,10 @@ set( CMAKE_Fortran_FLAGS_INIT "{SFC_FLAGS} {FCBASEOPTS} {BYTESWAPIO}" )
set( CMAKE_C_FLAGS_INIT "{SCC_FLAGS} {CFLAGS_LOCAL}" )

# https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_FLAGS_CONFIG_INIT.html
set( CMAKE_Fortran_FLAGS_Debug_INIT "{FCDEBUG}" )
set( CMAKE_Fortran_FLAGS_Release_INIT "" )
set( CMAKE_C_FLAGS_Debug_INIT "" )
set( CMAKE_C_FLAGS_Release_INIT "" )
set( CMAKE_Fortran_FLAGS_DEBUG_INIT "{FCDEBUG}" )
set( CMAKE_Fortran_FLAGS_RELEASE_INIT "" )
set( CMAKE_C_FLAGS_DEBUG_INIT "" )
set( CMAKE_C_FLAGS_RELEASE_INIT "" )

# Project specifics now
set( WRF_MPI_Fortran_FLAGS "{DM_FC_FLAGS}" )
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2 changes: 2 additions & 0 deletions frame/CMakeLists.txt
Original file line number Diff line number Diff line change
Expand Up @@ -156,6 +156,8 @@ target_sources(
# Disable optimizations on these files always
set_source_files_properties(
${nl_dyn_source}
module_comm_nesting_dm.F
DIRECTORY ${PROJECT_SOURCE_DIR}
PROPERTIES
COMPILE_OPTIONS_OPTIMIZATION
$<$<COMPILE_LANGUAGE:Fortran>:${WRF_FCNOOPT}>
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