Add initial CI capabilities

.github/workflows/ci.yml

@@ -0,0 +1,59 @@
+name: CI
+
+on:
+  push:
+    branches: ["master"]
+  pull_request:
+    branches: ["**"]
+    types: [opened, reopened, synchronize, labeled, unlabeled]
+  workflow_dispatch:
+
+jobs:
+  require-label:
+    name: Require Run CI label
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    steps:
+      - name: Ensure Run CI label is present
+        env:
+          HAS_LABEL: ${{ contains(github.event.pull_request.labels.*.name, 'Run CI') }}
+        run: |
+          if [ "${HAS_LABEL}" != "true" ]; then
+            echo "::error::Add the 'Run CI' label to this pull request to trigger CI."
+            exit 1
+          fi
+        shell: bash
+
+  build-and-check:
+    name: Build & Check (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    needs: [require-label]
+    if: github.event_name != 'pull_request' || needs.require-label.result == 'success'
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        shell: bash
+        run: |
+          if [[ "${RUNNER_OS}" == "Linux" ]]; then
+            sudo apt-get update
+            sudo apt-get install -y mpich
+          else
+            brew update
+            brew install open-mpi
+          fi
+
+      - name: Configure (Debug)
+        run: cmake -S src -B build -DHYPRE_BUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Debug
+
+      - name: Build
+        run: cmake --build build --parallel
+
+      - name: Run check target
+        run: cmake --build build --target check
+

src/docs/usr-manual/ch-misc.rst

@@ -895,7 +895,6 @@ errors. To only clear a specific error code, the user can call
 ``--with-print-errors`` or ``-DHYPRE_ENABLE_PRINT_ERRORS=ON``, additional error
 information will be printed to the standard error during execution.
 
-
 Bug Reporting and General Support
 ==============================================================================
 

src/docs/wiki-dev/CI.md

@@ -0,0 +1,98 @@
+This document gives information on Continuous Integration (CI) in hypre.
+
+# Continuous Integration Workflow
+
+The hypre repository includes an intentionally simple GitHub Actions
+workflow (`.github/workflows/ci.yml`) that provides a deterministic
+Debug build and the `check` regression target on both Linux and macOS.
+Understanding how this CI policy operates is essential when opening pull
+requests (PRs), because the CI status is required before changes may be
+merged into `master`.
+
+## Trigger conditions
+
+The workflow runs automatically for:
+
+-   pushes to `master` (to protect the branch after merges),
+-   all PR events (`opened`, `reopened`, `synchronize`) **and** label
+    changes (`labeled` / `unlabeled`),
+-   the manual `workflow_dispatch` action (a maintainer can explicitly
+    re-run CI from the "Run workflow" button in the GitHub UI).
+
+## Label requirement
+
+Every PR must carry the label `Run CI` before the build begins. A
+lightweight `require-label` job validates the label, and if it is
+missing the workflow fails immediately with a clear message:
+
+``` text
+Add the 'Run CI' label to this pull request to trigger CI.
+```
+
+Because label changes are part of the trigger set, adding (or re-adding)
+`Run CI` automatically restarts the workflow. Developers should
+therefore:
+
+1.  Draft the PR.
+2.  Apply the `Run CI` label once the branch is ready for testing.
+3.  Re-apply the label after pushing new commits if the workflow needs
+    to be restarted (or use the manual dispatch button).
+
+## Workflow structure
+
+The following jobs run in sequence:
+
+`require-label`
+
+:   *Runs only on PR events.* This job inspects the label list and fails
+    fast if `Run CI` is absent. The downstream build job is skipped when
+    this happens, which keeps GitHub's check list concise.
+
+`build-and-check`
+
+:   A matrix job covering `ubuntu-latest` and `macos-latest`. Each
+    worker:
+
+    1.  Checks out the hypre sources.
+    2.  Installs MPI runtime dependencies (`mpich` via `apt` on Ubuntu
+        and `open-mpi` via Homebrew on macOS) so that `mpiexec` is
+        available.
+    3.  Configures a Debug CMake build from `src` into `build` with
+        tests enabled.
+    4.  Builds the library with `cmake --build build --parallel`.
+    5.  Invokes `cmake --build build --target check` to run simple tests
+        using each of the three conceptual interfaces in hypre: IJ,
+        Struct, and SStruct.
+    6.  Optionally, you can download GitHub Actions runner logs to help
+        diagnose failures.
+
+## Helpful GitHub links
+
+When you need background on GitHub Actions terminology or you want to
+inspect a specific hypre workflow run, the following references collect
+the most useful starting points:
+
+-   **Understanding GitHub Actions** -- GitHub\'s introductory guide
+    explains the terminology (workflows, jobs, runners, etc.) at
+    [Understanding GitHub
+    Actions](https://docs.github.com/en/actions/get-started/understand-github-actions).
+-   **Understanding GitHub Continuous Integration** -- GitHub\'s CI
+    overview describes how event triggers and test automation work in
+    practice: [Understanding CI with GitHub
+    Actions](https://docs.github.com/en/actions/get-started/continuous-integration).
+-   **Writing workflows** -- GitHub\'s guide on using workflow templates
+    explains how to create and customize workflows: [Using workflow
+    templates](https://docs.github.com/en/actions/how-tos/write-workflows/use-workflow-templates).
+-   **Actions dashboard** -- [Actions
+    dashboard](https://github.com/hypre-space/hypre/actions) shows the
+    full history of workflow runs. Filter by branch or event and click a
+    row to open detailed logs.
+-   **Specific workflow page** -- [CI workflow
+    page](https://github.com/hypre-space/hypre/actions/workflows/ci.yml)
+    focuses on the main CI workflow currently in place. Use the \"Run
+    workflow\" button for a manual `workflow_dispatch` when needed.
+-   **Pull request checks tab** -- Each PR includes a \"Checks\" tab
+    that aggregates the `require-label` and matrix results. Expand a
+    failing job to view the captured console output or re-run a subset
+    of jobs. Example: [PR #1426 checks
+    page](https://github.com/hypre-space/hypre/pull/1426/checks).