First omp

CMakeLists.txt

@@ -8,31 +8,118 @@ project(panic LANGUAGES CXX)
 # Uses C++11
 set(CMAKE_CXX_STANDARD 11)
 
-# This makes it so it uses C++11, and fails if now found.
+# This makes it so it uses C++11, and fails if not found.
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 # Makes sure it uses basic options
-# -std=c++11 instead of -std-gnu++11
+# -std=c++11 instead of -std=gnu++11
 set(CMAKE_CXX_EXTENSIONS OFF)
 
+#---------------------------------------------------------------------------------------------------------------------------
+# OPENMP CONFIGURATION
+#---------------------------------------------------------------------------------------------------------------------------
+
+# OpenMP is disabled by default.
+# Enable with:
+# cmake -S . -B build -DPANIC_ENABLE_OPENMP=ON
+option(PANIC_ENABLE_OPENMP "Enable OpenMP support" OFF)
+
+# Number of OpenMP threads.
+# 0 means OpenMP decides the default.
+# Example that overrides default is: "-DPANIC_OMP_NUM_THREADS=":
+# cmake -S . -B build -DPANIC_ENABLE_OPENMP=ON -DPANIC_OMP_NUM_THREADS=4
+set(PANIC_OMP_NUM_THREADS "0" CACHE STRING "Number of OpenMP threads. 0 means OpenMP default.")
+
+#---------------------------------------------------------------------------------------------------------------------------
+# SOURCE FILES
+#---------------------------------------------------------------------------------------------------------------------------
 
 # This finds all the .cpp files in the src/ folder
-# and it's subfolders.
-# This is saved in the variale PANIC_SOURCES
+# and its subfolders.
+# This is saved in the variable PANIC_SOURCES
 file(GLOB_RECURSE PANIC_SOURCES CONFIGURE_DEPENDS
     src/*.cpp
 )
 
+#---------------------------------------------------------------------------------------------------------------------------
+# EXECUTABLE
+#---------------------------------------------------------------------------------------------------------------------------
 
 # Creates an executable called "panic"
-# It's build from main.cpp and all scr/
+# It's built from main.cpp and all src/
 add_executable(panic
     main.cpp
     ${PANIC_SOURCES}
 )
 
-# This finds all the .hpp files in the include/ folder
-# and it's subfolders.
+#---------------------------------------------------------------------------------------------------------------------------
+# INCLUDE DIRECTORIES
+#---------------------------------------------------------------------------------------------------------------------------
+
+# Tells the compiler where to look for header files.
+# This makes includes like <core/types.hpp> work.
 target_include_directories(panic PRIVATE
     ${CMAKE_CURRENT_SOURCE_DIR}/include
-)
+)
+
+#---------------------------------------------------------------------------------------------------------------------------
+# OPENMP BUILD SETTINGS
+#---------------------------------------------------------------------------------------------------------------------------
+
+# If the user enabled OpenMP with:
+#   -DPANIC_ENABLE_OPENMP=ON
+if(PANIC_ENABLE_OPENMP)
+
+    # Ask CMake to search for OpenMP support for the compiler.
+    # If found, CMake creates the target:
+    #   OpenMP::OpenMP_CXX
+    # This target contains the needed compiler and linker flags.
+    find_package(OpenMP)
+
+    # Check if CMake found OpenMP for C++.
+    if(OpenMP_CXX_FOUND)
+
+        # Link the panic executable with OpenMP.
+        # This adds the correct compiler/linker options, for example -fopenmp.
+        target_link_libraries(panic PRIVATE OpenMP::OpenMP_CXX)
+
+        # Define preprocessor macros that the C++ code can read.
+        #
+        # This makes the compiler behave as if every .cpp file had:
+        #   #define PANIC_USE_OPENMP 1
+        #   #define PANIC_OMP_NUM_THREADS <value from CMake>
+        #
+        # Example:
+        #   -DPANIC_OMP_NUM_THREADS=4
+        #
+        # becomes:
+        #   #define PANIC_OMP_NUM_THREADS 4
+        target_compile_definitions(panic PRIVATE
+            PANIC_USE_OPENMP=1
+            PANIC_OMP_NUM_THREADS=${PANIC_OMP_NUM_THREADS}
+        )
+
+    else()
+
+        # The user asked for OpenMP, but CMake could not find it.
+        # So we warn the user and build PANIC without OpenMP instead.
+        message(WARNING "OpenMP requested, but OpenMP was not found. Building without OpenMP.")
+
+        # Tell the C++ code that OpenMP is disabled.
+        target_compile_definitions(panic PRIVATE
+            PANIC_USE_OPENMP=0
+            PANIC_OMP_NUM_THREADS=0
+        )
+
+    endif()
+
+else()
+
+    # The user did not enable OpenMP.
+    # So PANIC builds as normal serial/portable code.
+    target_compile_definitions(panic PRIVATE
+        PANIC_USE_OPENMP=0
+        PANIC_OMP_NUM_THREADS=0
+    )
+
+endif()