Add MPI

.github/workflows/mpi.yml

@@ -0,0 +1,53 @@
+name: MPI Galaxy Demo
+
+permissions:
+  contents: read
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+
+concurrency:
+  group: mpi-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  mpi-galaxy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install dependencies (MPI + HDF5 + Python)
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y mpich libhdf5-dev libomp-dev cmake build-essential python3
+
+      - name: Configure project (CMake)
+        run: |
+          mkdir -p build
+          cd build
+          cmake .. -DCMAKE_BUILD_TYPE=Release -DNEXT_FP64=ON -DNEXT_MPI=ON
+
+      - name: Build project
+        run: |
+          cd build
+          cmake --build . -- -j$(nproc)
+
+      - name: Run Galaxy demo (timed)
+        run: |
+          # Go back to project root
+          cd $GITHUB_WORKSPACE/examples/GalaxyDemo
+          python3 galaxy.py
+          # Run with 2 MPI ranks and 2 OpenMP threads, stop after 20s
+          timeout 60s mpiexec -n 2 ../../next galaxy.txt 1 0.01 0.1 hdf5 || true
+
+      - name: Upload simulation outputs
+        uses: actions/upload-artifact@v4
+        with:
+          name: galaxy-dumps
+          path: |
+            examples/GalaxyDemo/dump_*.hdf5
+            examples/GalaxyDemo/dump_*.xdmf

CMakeLists.txt

@@ -11,41 +11,41 @@ if (MINGW)
 elseif (MSVC)
     message(STATUS "Detected MSVC — using MSVC settings")
     set(USING_MSVC TRUE)
+elseif (APPLE)
+    message(STATUS "Detected macOS — limited MPI support")
+    set(USING_APPLE TRUE)
+elseif (UNIX)
+    message(STATUS "Detected Linux/UNIX — using standard settings")
+    set(USING_UNIX TRUE)
 endif()
 
 # ============================
 # Options
 # ============================
 option(NEXT_FP32 "Use 32-bit floats (scalar)" OFF)
 option(NEXT_FP64 "Use 64-bit floats (scalar)" ON)
+option(NEXT_MPI "Enable MPI support" OFF)
 
-# Option: copy final executable to source dir
 option(NEXT_COPY_TO_CMAKE_SOURCE_DIR "Copy final executable from build dir to source dir" ON)
 
 # ============================
 # Precision modes
 # ============================
-set(NEXT_MODES
-    NEXT_FP32
-    NEXT_FP64
-)
+set(NEXT_MODES NEXT_FP32 NEXT_FP64)
 
-# Count enabled modes
 set(NEXT_MODE_COUNT 0)
 foreach(m ${NEXT_MODES})
     if(${m})
         math(EXPR NEXT_MODE_COUNT "${NEXT_MODE_COUNT} + 1")
     endif()
 endforeach()
 
-# Enforce exactly one mode
 if(NEXT_MODE_COUNT EQUAL 0)
     message(FATAL_ERROR "You must enable NEXT_FP64 or NEXT_FP32.")
 elseif(NEXT_MODE_COUNT GREATER 1)
     message(FATAL_ERROR "Enable only one precision mode.")
 endif()
 
-# Apply compile definitions
 if(NEXT_FP32)
     add_compile_definitions(NEXT_FP32)
 elseif(NEXT_FP64)
@@ -62,7 +62,10 @@ file(GLOB ARGPARSE_FILES ${CMAKE_SOURCE_DIR}/argparse/*.cpp)
 
 add_executable(next ${SRC_FILES} ${ARGPARSE_FILES})
 
-option(ENABLE_VEC_REPORT "Enable compiler vectorization reports" ON)
+# ============================
+# Vectorization reports
+# ============================
+option(ENABLE_VEC_REPORT "Enable compiler vectorization reports" OFF)
 
 if(ENABLE_VEC_REPORT)
     if(CMAKE_CXX_COMPILER_ID MATCHES "IntelLLVM")
@@ -74,38 +77,56 @@ if(ENABLE_VEC_REPORT)
     endif()
 endif()
 
-
 # ============================
 # OpenMP
 # ============================
 find_package(OpenMP QUIET)
 if(OpenMP_CXX_FOUND)
     message(STATUS "OpenMP detected — enabling multithreading.")
-
     if(MSVC)
-        # Force MSVC to use the modern LLVM backend (supports OpenMP 3.0+ and size_t)
-        # We add it as a compiler option because MSVC's default find_package 
-        # often defaults to the legacy /openmp flag.
         target_compile_options(next PRIVATE /openmp:llvm)
     else()
         target_link_libraries(next PRIVATE OpenMP::OpenMP_CXX)
     endif()
-
 else()
     message(STATUS "OpenMP not found — building in single-threaded mode.")
 endif()
 
+# ============================
+# MPI detection
+# ============================
+if(NEXT_MPI)
+    if(USING_UNIX)
+        # Linux: standard OpenMPI
+        find_package(MPI REQUIRED)
+        message(STATUS "MPI (OpenMPI) detected — enabling distributed memory parallelism.")
+        target_compile_definitions(next PRIVATE NEXT_MPI)
+        target_link_libraries(next PRIVATE MPI::MPI_CXX)
+
+    elseif(USING_MSVC OR USING_MINGW)
+        # Windows: Microsoft MPI
+        find_package(MPI REQUIRED)
+        message(STATUS "MPI (MS-MPI) detected — enabling distributed memory parallelism.")
+        target_compile_definitions(next PRIVATE NEXT_MPI)
+        target_link_libraries(next PRIVATE MPI::MPI_CXX)
+
+    elseif(USING_APPLE)
+        message(WARNING "MPI requested, but macOS does not ship MPI by default. Please install OpenMPI via Homebrew (brew install open-mpi).")
+        find_package(MPI REQUIRED)
+        target_compile_definitions(next PRIVATE NEXT_MPI)
+        target_link_libraries(next PRIVATE MPI::MPI_CXX)
+    endif()
+endif()
+
 # ============================
 # HDF5 detection
 # ============================
-# MSVC: use vcpkg or prebuilt binaries
 if (USING_MSVC AND DEFINED ENV{HDF5_DIR})
     set(HDF5_ROOT "$ENV{HDF5_DIR}")
     set(CMAKE_PREFIX_PATH "${HDF5_ROOT};${CMAKE_PREFIX_PATH}")
 endif()
 
 if (USING_MINGW)
-    # MSYS2 MinGW installs HDF5 here
     set(CMAKE_PREFIX_PATH "C:/tools/msys64/mingw64")
     message(STATUS "Using MSYS2 MinGW HDF5 path: ${CMAKE_PREFIX_PATH}")
 endif()

argparse/argparse.cpp

@@ -1,33 +1,59 @@
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 #include "argparse.hpp"
 #include <iostream>
 #include <stdexcept>
+#ifdef NEXT_MPI
+    #include <mpi.h>
+#endif
 
 namespace next {
 
-Arguments parse_arguments(int argc, char** argv)
+Arguments parse_arguments(int argc, char** argv, int rank)
 {
     if (argc != 6) {
-        std::cerr << "Usage: next <input.txt> <threads> <dt> <dump_interval> <vtk|vtu|hdf5>\n";
+        // Only rank 0 prints usage
+        if (rank == 0) {
+            std::cerr << "Usage: next <input.txt> <threads> <dt> <dump_interval> <vtk|vtu|hdf5>\n";
+        }
+
+#ifdef NEXT_MPI
+        MPI_Finalize();
+#endif
         std::exit(1);
     }
 
     Arguments args;
 
-    args.input_file = argv[1];
-    args.threads = std::stoi(argv[2]);
-    args.dt = std::stod(argv[3]);
+    args.input_file    = argv[1];
+    args.threads       = std::stoi(argv[2]);
+    args.dt            = std::stod(argv[3]);
     args.dump_interval = std::stod(argv[4]);
 
     std::string fmt = argv[5];
 
-    if (fmt == "vtk")
+    if (fmt == "vtk") {
         args.format = OutputFormat::VTK;
-    else if (fmt == "vtu")
+    } else if (fmt == "vtu") {
         args.format = OutputFormat::VTU;
-    else if (fmt == "hdf5")
+    } else if (fmt == "hdf5") {
         args.format = OutputFormat::HDF5;
-    else {
-        std::cerr << "Choose a file format: vtk, vtu, or hdf5\n";
+    } else {
+        if (rank == 0) {
+            std::cerr << "Choose a file format: vtk, vtu, or hdf5\n";
+        }
+#ifdef NEXT_MPI
+        MPI_Finalize();
+#endif
         std::exit(1);
     }
 

argparse/argparse.hpp

@@ -17,6 +17,6 @@ struct Arguments {
     OutputFormat format;
 };
 
-Arguments parse_arguments(int argc, char** argv);
+Arguments parse_arguments(int argc, char** argv, int rank);
 
 }