Major refactoring

.github/workflows/ci.yml

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+name: CI
+
+# Run on every push and pull request so each commit is validated.
+on:
+  push:
+  pull_request:
+
+# Cancel an in-progress run if a newer commit is pushed to the same ref.
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: build • test • coverage (OpenMPI)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    env:
+      # GitHub-hosted runners have fewer cores than the 8 ranks some suites
+      # launch, so allow MPI to oversubscribe.  (rmaps_base for OpenMPI 4.x,
+      # the PRTE policy for OpenMPI 5.x — setting the unused one is harmless.)
+      OMPI_MCA_rmaps_base_oversubscribe: "1"
+      PRTE_MCA_rmaps_default_mapping_policy: ":oversubscribe"
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install toolchain (CMake, OpenMPI, gcovr)
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            cmake build-essential openmpi-bin libopenmpi-dev gcovr
+
+      - name: Configure (tests + coverage)
+        run: cmake -B build -DBLINK_TESTS=ON -DBLINK_COVERAGE=ON
+
+      - name: Build
+        run: cmake --build build -j"$(nproc)"
+
+      - name: Run tests
+        run: ctest --test-dir build --output-on-failure --no-tests=error
+
+      # ---- coverage (best-effort: never flips the test verdict) ----
+      - name: Coverage report (gcovr)
+        if: always()
+        continue-on-error: true
+        run: |
+          gcovr --root . --filter 'src/' \
+                --exclude-unreachable-branches --exclude-throw-branches \
+                --exclude-lines-by-pattern '.*MPI_Abort.*' \
+                --xml-pretty -o coverage.xml \
+                --print-summary | tee coverage_summary.txt
+          {
+            echo '## Coverage (src/)'
+            echo '```'
+            cat coverage_summary.txt
+            echo '```'
+          } >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload coverage to Codecov
+        if: always()
+        continue-on-error: true
+        uses: codecov/codecov-action@v4
+        with:
+          files: coverage.xml
+          fail_ci_if_error: false
+        env:
+          # Optional: set this repo secret to enable Codecov uploads/badge.
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+
+      - name: Upload coverage artifact
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: |
+            coverage.xml
+            coverage_summary.txt
+          if-no-files-found: ignore

.github/workflows/codeql.yml

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+name: CodeQL
+
+# Static analysis for C/C++.  Runs on pushes/PRs to the main branches and
+# weekly (to catch newly-published queries against unchanged code).
+on:
+  push:
+    branches: [ main, dev ]
+  pull_request:
+    branches: [ main, dev ]
+  schedule:
+    - cron: '0 6 * * 1'   # Mondays 06:00 UTC
+
+jobs:
+  analyze:
+    name: Analyze (c-cpp)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      security-events: write   # upload results to the Security tab
+      actions: read
+      contents: read
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install build dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            cmake build-essential openmpi-bin libopenmpi-dev
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: c-cpp
+
+      # Manual build (more reliable than autobuild for a CMake+MPI project).
+      # Tests are off so CodeQL focuses on the benchmark sources, not GTest.
+      - name: Build
+        run: |
+          cmake -B build -DBLINK_TESTS=OFF
+          cmake --build build -j"$(nproc)"
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:c-cpp"

.gitignore

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+build/
+build*/
+
+# coverage artifacts (generated; uploaded to Codecov by CI, never committed)
+coverage.xml
+coverage*.html
+*.gcda
+*.gcno
+*.gcov

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(blink C CXX)
+
+# On HPC systems where CC/CXX are already MPI wrappers (mpicc/mpicxx),
+# FindMPI's link-test often fails because LD_LIBRARY_PATH isn't set up for
+# CMake's subprocess.  Pass -DBLINK_MPI_WRAPPER=ON to skip FindMPI and create
+# stub INTERFACE targets instead — the wrapper already injects all flags.
+option(BLINK_MPI_WRAPPER
+    "Assume CC/CXX are MPI compiler wrappers; skip find_package(MPI)" OFF)
+
+if(BLINK_MPI_WRAPPER)
+    # Prefer $ENV{MPICC} (always correct on HPC modules) over CMAKE_C_COMPILER
+    # (which may be the underlying gcc if the CMake cache is stale).
+    if(DEFINED ENV{MPICC})
+        set(_mpi_cc "$ENV{MPICC}")
+    elseif(CMAKE_C_COMPILER MATCHES "mpi")
+        set(_mpi_cc "${CMAKE_C_COMPILER}")
+    else()
+        find_program(_mpi_cc NAMES mpicc DOC "MPI C compiler wrapper")
+    endif()
+    if(NOT _mpi_cc)
+        message(FATAL_ERROR
+            "BLINK_MPI_WRAPPER=ON but no MPI wrapper found.\n"
+            "Set the MPICC environment variable or put mpicc on PATH.")
+    endif()
+    message(STATUS "BLINK_MPI_WRAPPER=ON — querying '${_mpi_cc}' for MPI flags")
+    execute_process(COMMAND "${_mpi_cc}" --showme:incdirs
+                    OUTPUT_VARIABLE _mpi_incdirs OUTPUT_STRIP_TRAILING_WHITESPACE ERROR_QUIET)
+    execute_process(COMMAND "${_mpi_cc}" --showme:libdirs
+                    OUTPUT_VARIABLE _mpi_libdirs OUTPUT_STRIP_TRAILING_WHITESPACE ERROR_QUIET)
+    execute_process(COMMAND "${_mpi_cc}" --showme:libs
+                    OUTPUT_VARIABLE _mpi_libs    OUTPUT_STRIP_TRAILING_WHITESPACE ERROR_QUIET)
+    if(NOT _mpi_incdirs OR NOT _mpi_libdirs)
+        message(FATAL_ERROR
+            "MPI wrapper '${_mpi_cc}' did not return include/lib dirs.\n"
+            "Check that it supports --showme:incdirs (OpenMPI wrapper required).")
+    endif()
+    string(REPLACE " " ";" _mpi_incdirs "${_mpi_incdirs}")
+    string(REPLACE " " ";" _mpi_libdirs "${_mpi_libdirs}")
+    string(REPLACE " " ";" _mpi_libs    "${_mpi_libs}")
+    set(_mpi_lib_flags "")
+    foreach(_l ${_mpi_libs})
+        list(APPEND _mpi_lib_flags "-l${_l}")
+    endforeach()
+    message(STATUS "  includes : ${_mpi_incdirs}")
+    message(STATUS "  libdirs  : ${_mpi_libdirs}")
+    message(STATUS "  libs     : ${_mpi_lib_flags}")
+    foreach(_tgt MPI::MPI_C MPI::MPI_CXX)
+        if(NOT TARGET ${_tgt})
+            add_library(${_tgt} INTERFACE IMPORTED)
+        endif()
+        set_target_properties(${_tgt} PROPERTIES
+            INTERFACE_INCLUDE_DIRECTORIES "${_mpi_incdirs}"
+            INTERFACE_LINK_DIRECTORIES    "${_mpi_libdirs}"
+            INTERFACE_LINK_LIBRARIES      "${_mpi_lib_flags}")
+    endforeach()
+else()
+    find_package(MPI REQUIRED COMPONENTS C CXX)
+endif()
+
+# All binaries land in <build>/bin/
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+
+# Default to Release so -O3 is active unless the user overrides
+if(NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type" FORCE)
+endif()
+
+option(BLINK_COVERAGE "Build with gcov coverage instrumentation (-O0 --coverage)" OFF)
+if(BLINK_COVERAGE)
+    # -O0 for accurate line attribution; atomic counter updates so the multiple
+    # concurrent MPI ranks of a single benchmark binary don't corrupt the shared
+    # .gcda files when they dump coverage on exit.
+    add_compile_options(-O0 -g --coverage -fprofile-update=atomic)
+    add_link_options(--coverage)
+else()
+    add_compile_options(-O3)
+endif()
+add_compile_definitions(_GNU_SOURCE)
+
+add_subdirectory(src)
+
+option(BLINK_TESTS "Build correctness tests (requires GTest)" ON)
+
+if(BLINK_TESTS)
+    find_package(GTest QUIET)
+    if(NOT GTest_FOUND)
+        message(STATUS "GTest not found via find_package — fetching with FetchContent")
+        include(FetchContent)
+        FetchContent_Declare(
+            googletest
+            GIT_REPOSITORY https://github.com/google/googletest.git
+            GIT_TAG        v1.14.0
+        )
+        set(INSTALL_GTEST OFF CACHE BOOL "" FORCE)
+        FetchContent_MakeAvailable(googletest)
+        if(NOT TARGET GTest::GTest)
+            add_library(GTest::GTest ALIAS gtest)
+            add_library(GTest::Main  ALIAS gtest_main)
+        endif()
+        set(GTest_FOUND TRUE)
+    endif()
+
+    if(GTest_FOUND)
+        enable_testing()
+        add_subdirectory(tests)
+        message(STATUS "GTest ready — correctness tests enabled (run: ctest --test-dir build)")
+    else()
+        message(WARNING "GTest unavailable — correctness tests skipped (pass -DBLINK_TESTS=OFF to silence)")
+    endif()
+else()
+    message(STATUS "BLINK_TESTS=OFF — correctness tests skipped")
+endif()

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024-2026 HLC-Lab
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.