Add waLBerla as a submodule

.gitmodules

+[submodule "external/walberla"]
+	path = external/walberla
+	url = https://i10git.cs.fau.de/walberla/walberla.git

CMakeLists.txt

@@ -9,6 +9,7 @@ set(CMAKE_CXX_FLAGS_RELEASE "-O3")
 set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -DDEBUG")
 
 option(USE_MPI                      "USE_MPI" ON)
+option(USE_WALBERLA                 "Enable waLBerla support for using BlockForest domain partitioning and dynamic load balancing" OFF)
 option(COMPILE_CUDA                 "COMPILE_CUDA" OFF)
 set(USER_SOURCE_FILES "" CACHE STRING "List of source files to compile (semicolon-separated)")
 
@@ -96,14 +97,8 @@ endif()
 #================================================================================
 # waLBerla ======================================================================
 #================================================================================
-set(WALBERLA_DIR ${WALBERLA_DIR} CACHE PATH "Path to waLBerla source directory (required only when using BlockForest partitioning).")
-
-if(WALBERLA_DIR)
-    if(EXISTS "${WALBERLA_DIR}")
-        target_compile_definitions(${PAIRS_TARGET} PUBLIC USE_WALBERLA)
-    else()
-        message(FATAL_ERROR "Invalid WALBERLA_DIR: '${WALBERLA_DIR}' does not exist.")
-    endif()
+if(USE_WALBERLA)
+    target_compile_definitions(${PAIRS_TARGET} PUBLIC USE_WALBERLA)
 
     set(RUNTIME_WALBERLA_FILES
         runtime/domain/block_forest.cpp
@@ -115,13 +110,14 @@ if(WALBERLA_DIR)
     else()
         list(APPEND RUNTIME_WALBERLA_FILES runtime/boundary_weights.cpp)
     endif()
-
+    
     target_sources(${PAIRS_TARGET} PRIVATE ${RUNTIME_WALBERLA_FILES})
 
-    ## Linking walberla modules
-    set(PAIRS_WALBERLA_DEPENDENCIES walberla::blockforest walberla::core walberla::pe)
-    find_package(waLBerla REQUIRED)
-    set(WALBERLA_LINK_LIBRARIES_KEYWORD PUBLIC)
+    add_subdirectory(external/walberla EXCLUDE_FROM_ALL)
+    waLBerla_import()
+
+    # Recent issue from the waLBerla side: warnings about empty CUDA_ARCHITECTURES for walberla_gpu 
+    set(PAIRS_WALBERLA_DEPENDENCIES walberla::blockforest walberla::core)
     target_link_libraries(${PAIRS_TARGET} PUBLIC ${PAIRS_WALBERLA_DEPENDENCIES})
 
     ## TODO: PAIRS_LINK_DIRS and PAIRS_LINK_LIBRARIES for walberla modules *AND* their dependencies

cmake/FindwaLBerla.cmake

-if ( WALBERLA_DIR )
-    # WALBERLA_DIR has to point to the waLBerla source directory
-    # this command builds waLBerla (again) in the current build directory in the subfolder "walberla" (second argument)
-    add_subdirectory( ${WALBERLA_DIR} walberla EXCLUDE_FROM_ALL)
-    
-    waLBerla_import()
-    # Adds the 'src' and 'tests' directory of current app
-    list( APPEND WALBERLA_MODULE_DIRS "${CMAKE_SOURCE_DIR}/src" "${CMAKE_SOURCE_DIR}/tests" )
-    list( REMOVE_DUPLICATES  WALBERLA_MODULE_DIRS )
-    set ( WALBERLA_MODULE_DIRS  ${WALBERLA_MODULE_DIRS} CACHE INTERNAL "All folders that contain modules or tests" )
-else()
-    message( FATAL_ERROR "waLBerla not found - Use 'cmake -DWALBERLA_DIR=path_to_waLBerla_sources  pathToApplicationSources' "  )
-endif()

runtime/domain/block_forest.cpp

@@ -255,13 +255,12 @@ void BlockForest::initialize(int *argc, char ***argv) {
     rank = mpiManager->rank();
     
     auto block_config = balance_workload ? walberla::Vector3<int>(1, 1, 1) : getBlockConfig();
-    auto procs = mpiManager->numProcesses();
-    auto ref_level = balance_workload ? getInitialRefinementLevel(procs) : 0;
+    auto ref_level = balance_workload ? getInitialRefinementLevel(world_size) : 0;
     
     // PBC's are forced to true here and sperately handled when determining ghosts 
     walberla::Vector3<bool> pbc(true, true, true);
     walberla::math::AABB domain(grid_min[0], grid_min[1], grid_min[2], grid_max[0], grid_max[1], grid_max[2]);
-    forest = walberla::blockforest::createBlockForest(domain, block_config, pbc, procs, ref_level);
+    forest = walberla::blockforest::createBlockForest(domain, block_config, pbc, world_size, ref_level);
 
     this->info = make_shared<walberla::blockforest::InfoCollection>();