ci: reduce setup overhead and parallelize Windows compilation

.github/actions/setup-clang/action.yml

@@ -1,10 +1,16 @@
 name: Set up Clang 23
 description: Install the pinned compiler, analysis, formatting and OpenMP tools on Ubuntu.
+inputs:
+  format-only:
+    description: Install only clang-format for formatting checks.
+    default: "false"
 runs:
   using: composite
   steps:
     - name: Install LLVM 23 tools
       shell: bash
+      env:
+        FORMAT_ONLY: ${{ inputs.format-only }}
       run: |
         set -euo pipefail
         # shellcheck source=/dev/null
@@ -14,7 +20,15 @@ runs:
         echo "deb [signed-by=/usr/share/keyrings/apt.llvm.org.asc] https://apt.llvm.org/$VERSION_CODENAME/ llvm-toolchain-$VERSION_CODENAME-23 main" \
           | sudo tee /etc/apt/sources.list.d/llvm-23.list >/dev/null
         sudo apt-get update -qq
-        sudo apt-get install -y clang-23 clang-format-23 clang-tidy-23 libomp-23-dev cmake ninja-build
-        clang++-23 --version
+        packages=(clang-format-23)
+        if [[ "$FORMAT_ONLY" != true ]]; then
+          packages+=(clang-23 clang-tidy-23 libomp-23-dev)
+        fi
+        sudo apt-get install -y "${packages[@]}"
         clang-format-23 --version
-        clang-tidy-23 --version
+        if [[ "$FORMAT_ONLY" != true ]]; then
+          clang++-23 --version
+          clang-tidy-23 --version
+          cmake --version
+          ninja --version
+        fi

.github/scripts/test_setup_clang.py

@@ -0,0 +1,99 @@
+"""Exercise LLVM package selection and failure propagation without installing tools."""
+
+import json
+import os
+import subprocess
+import sys
+import tempfile
+import textwrap
+import unittest
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+class ClangSetupTest(unittest.TestCase):
+    def test_selected_tools_and_install_failures(self):
+        action = (ROOT / ".github/actions/setup-clang/action.yml").read_text()
+        self.assertIn('default: "false"', action)
+        self.assertIn("FORMAT_ONLY: ${{ inputs.format-only }}", action)
+        command = textwrap.dedent(action.split("      run: |\n", 1)[1])
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            log = root / "commands.jsonl"
+            for tool in (
+                "sudo",
+                "curl",
+                "clang-format-23",
+                "clang++-23",
+                "clang-tidy-23",
+                "cmake",
+                "ninja",
+            ):
+                helper = root / tool
+                helper.write_text(
+                    f"#!{sys.executable}\n"
+                    "import json, os, sys\n"
+                    "from pathlib import Path\n"
+                    "name = Path(sys.argv[0]).name\n"
+                    "with open(os.environ['SETUP_LOG'], 'a') as stream:\n"
+                    "    stream.write(json.dumps([name, *sys.argv[1:]]) + '\\n')\n"
+                    "if name == os.environ.get('FAIL_TOOL'):\n"
+                    "    sys.exit(7)\n"
+                    "if os.environ.get('FAIL_TOOL') == 'install' and "
+                    "sys.argv[1:3] == ['apt-get', 'install']:\n"
+                    "    sys.exit(7)\n"
+                    "if name == 'curl':\n"
+                    "    print('test-key')\n"
+                    "if name == 'sudo' and sys.argv[1] == 'tee':\n"
+                    "    sys.stdin.read()\n"
+                )
+                helper.chmod(0o755)
+            for mode, failure in (
+                ("false", ""),
+                ("true", ""),
+                ("false", "install"),
+                ("true", "install"),
+                ("true", "clang-format-23"),
+                ("false", "clang-tidy-23"),
+            ):
+                with self.subTest(format_only=mode, failure=failure):
+                    log.unlink(missing_ok=True)
+                    result = subprocess.run(
+                        ["bash", "-c", command],
+                        env=dict(
+                            os.environ,
+                            PATH=str(root) + os.pathsep + os.environ["PATH"],
+                            FORMAT_ONLY=mode,
+                            SETUP_LOG=str(log),
+                            FAIL_TOOL=failure,
+                        ),
+                        capture_output=True,
+                        text=True,
+                        check=False,
+                    )
+                    self.assertEqual(result.returncode == 0, not failure)
+                    calls = [json.loads(line) for line in log.read_text().splitlines()]
+                    if failure:
+                        self.assertFalse(any(call[0] == "ninja" for call in calls))
+                        continue
+                    packages = next(
+                        call[4:]
+                        for call in calls
+                        if call[:4] == ["sudo", "apt-get", "install", "-y"]
+                    )
+                    expected = {"clang-format-23"}
+                    if mode == "false":
+                        expected.update(("clang-23", "clang-tidy-23", "libomp-23-dev"))
+                    self.assertEqual(set(packages), expected)
+                    versions = {call[0] for call in calls if call[1:] == ["--version"]}
+                    expected = {"clang-format-23"}
+                    if mode == "false":
+                        expected.update(
+                            ("clang++-23", "clang-tidy-23", "cmake", "ninja")
+                        )
+                    self.assertEqual(versions, expected)
+
+
+if __name__ == "__main__":
+    unittest.main()

.github/workflows/python.yml

@@ -59,8 +59,8 @@ jobs:
           python-version: ${{ matrix.python-version }}
           cache: pip
 
-      - name: Install system dependencies
-        run: sudo apt-get update -qq && sudo apt-get install -y cmake
+      - name: Verify runner CMake
+        run: cmake --version
 
       - name: Upgrade pip
         run: pip install --upgrade pip
@@ -136,8 +136,8 @@ jobs:
         with:
           python-version: "3.11"
           cache: pip
-      - name: Install system dependencies
-        run: sudo apt-get update -qq && sudo apt-get install -y cmake
+      - name: Verify runner CMake
+        run: cmake --version
       - name: Install comparison dependencies
         run: python -m pip install ".[test]" faiss-cpu
       - name: Test comparison script

.github/workflows/test.yaml

@@ -22,6 +22,8 @@ jobs:
     steps:
       - uses: actions/checkout@v7
       - uses: ./.github/actions/setup-clang
+        with:
+          format-only: "true"
       - name: Check formatting
         run: ./scripts/check-format.sh
 
@@ -111,7 +113,8 @@ jobs:
           python-version: "3.11"
       - name: Install build dependencies
         run: |
-          sudo apt-get update -qq && sudo apt-get install -y cmake ninja-build
+          cmake --version
+          ninja --version
           python -m pip install "numpy>=1.23" "pybind11>=2.12"
       - name: Configure benchmark targets only
         run: >-
@@ -140,8 +143,10 @@ jobs:
       - uses: actions/setup-python@v7
         with:
           python-version: "3.11"
-      - name: Install dependencies
-        run: sudo apt-get update -qq && sudo apt-get install -y cmake ninja-build
+      - name: Verify runner build tools
+        run: |
+          cmake --version
+          ninja --version
       - name: Configure
         run: cmake -S . -B build -G Ninja -DRABITQ_BUILD_TESTS=ON -DRABITQ_BUILD_SAMPLES=ON -DCMAKE_BUILD_TYPE=Release
       - name: Build
@@ -251,6 +256,9 @@ jobs:
     name: Windows x86-64 (VS 2026)
     runs-on: windows-2025-vs2026
     timeout-minutes: 45
+    env:
+      # MSBuild's project parallelism alone does not parallelize source files.
+      CL: /MP2
     steps:
       - uses: actions/checkout@v7
       - name: Configure
@@ -278,8 +286,10 @@ jobs:
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v7
-      - name: Install dependencies
-        run: sudo apt-get update -qq && sudo apt-get install -y cmake ninja-build
+      - name: Verify runner build tools
+        run: |
+          cmake --version
+          ninja --version
       # Keep assertions/debug symbols while avoiding unoptimized sanitizer loops.
       - name: Configure
         run: >-
@@ -317,8 +327,10 @@ jobs:
     timeout-minutes: 15
     steps:
       - uses: actions/checkout@v7
-      - name: Install dependencies
-        run: sudo apt-get update -qq && sudo apt-get install -y cmake ninja-build
+      - name: Verify runner build tools
+        run: |
+          cmake --version
+          ninja --version
       - name: Build RaBitQ-Library with portable tests
         run: |
           cmake -S . -B build-install -G Ninja \
@@ -413,6 +425,7 @@ jobs:
         env:
           CMAKE_GENERATOR: Visual Studio 18 2026
           CMAKE_GENERATOR_PLATFORM: x64
+          CL: /MP2
         run: >-
           cmake "-DRABITQ_SOURCE_DIR=$PWD"
           "-DWORK_DIR=$env:RUNNER_TEMP/rabitq-core"