Skip nightly benchmarks if no new commits (#173)

This PR adds a file in the gh-pages benchmark data to store the commits
of fvdb-core and fvdb-reality-capture of the last benchmark run. It also
adds metadata for each run containing these commits.

The workflow is updated to check the current and previous commits and
not run if there are no new commits.

When there are no new commits this finishes within seconds:
https://github.com/openvdb/fvdb-reality-capture/actions/runs/19330065132/job/55290639222

---------

Signed-off-by: Mark Harris <mharris@nvidia.com>

Author: harrism

.github/workflows/nightly.yml

@@ -31,7 +31,14 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       fvdb_core_commit_hash: ${{ steps.get-commit-hash.outputs.fvdb_core_commit_hash }}
+      fvdb_reality_capture_commit_hash: ${{ steps.get-commit-hash.outputs.fvdb_reality_capture_commit_hash }}
+      should_skip: ${{ steps.check-changes.outputs.should_skip }}
     steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+          path: gh-pages
+
       - name: Get fvdb-core commit hash
         id: get-commit-hash
         env:
@@ -46,12 +53,50 @@ jobs:
           FVDB_CORE_COMMIT_HASH=$(gh api repos/openvdb/fvdb-core/commits/main --jq .sha)
           echo "FVDB_CORE_COMMIT_HASH=${FVDB_CORE_COMMIT_HASH}"
           echo "fvdb_core_commit_hash=${FVDB_CORE_COMMIT_HASH}" >> "$GITHUB_OUTPUT"
+
+          # Get fvdb-reality-capture commit hash (current commit)
+          FVDB_RC_COMMIT_HASH="${{ github.sha }}"
+          echo "FVDB_RC_COMMIT_HASH=${FVDB_RC_COMMIT_HASH}"
+          echo "fvdb_reality_capture_commit_hash=${FVDB_RC_COMMIT_HASH}" >> "$GITHUB_OUTPUT"
+
+      - name: Check if commits changed since last run
+        id: check-changes
+        run: |
+          SHOULD_SKIP="false"
+
+          if [ -f "gh-pages/dev/bench/last_run_commits.txt" ]; then
+            echo "Found last run commits file"
+            cat gh-pages/dev/bench/last_run_commits.txt
+
+            LAST_FVDB_CORE=$(grep "fvdb_core:" gh-pages/dev/bench/last_run_commits.txt | cut -d' ' -f2)
+            LAST_FVDB_RC=$(grep "fvdb_reality_capture:" gh-pages/dev/bench/last_run_commits.txt | cut -d' ' -f2)
+
+            CURRENT_FVDB_CORE="${{ steps.get-commit-hash.outputs.fvdb_core_commit_hash }}"
+            CURRENT_FVDB_RC="${{ steps.get-commit-hash.outputs.fvdb_reality_capture_commit_hash }}"
+
+            echo "Last run - fvdb-core: ${LAST_FVDB_CORE}, fvdb-reality-capture: ${LAST_FVDB_RC}"
+            echo "Current  - fvdb-core: ${CURRENT_FVDB_CORE}, fvdb-reality-capture: ${CURRENT_FVDB_RC}"
+
+            if [ -n "${LAST_FVDB_CORE}" ] && [ -n "${LAST_FVDB_RC}" ] && \
+              [ "${LAST_FVDB_CORE}" = "${CURRENT_FVDB_CORE}" ] && \
+              [ "${LAST_FVDB_RC}" = "${CURRENT_FVDB_RC}" ]; then
+              echo "No changes detected. Skipping workflow."
+              SHOULD_SKIP="true"
+            else
+              echo "Changes detected. Running workflow."
+            fi
+          else
+            echo "No previous run found. Running workflow."
+          fi
+
+          echo "should_skip=${SHOULD_SKIP}" >> "$GITHUB_OUTPUT"
   ##############################################################################
   # BUILD FVDB
   ##############################################################################
   start-build-runner:
-    if: ${{ github.repository == 'openvdb/fvdb-reality-capture' }}
+    if: ${{ github.repository == 'openvdb/fvdb-reality-capture' && needs.get-fvdb-core-commit-hash.outputs.should_skip != 'true' }}
     name: Start CPU-only EC2 runner for build
+    needs: get-fvdb-core-commit-hash
     runs-on: ubuntu-latest
     outputs:
       label: ${{ steps.start-build-runner.outputs.label }}
@@ -146,7 +191,7 @@ jobs:
           retention-days: 30
 
   fvdb-build-stop-runner:
-    if: ${{ always() && github.repository == 'openvdb/fvdb-reality-capture' }}
+    if: ${{ always() && github.repository == 'openvdb/fvdb-reality-capture' && needs.start-build-runner.result != 'skipped' }}
     name: Stop CPU-only EC2 runner for build
     needs:
       - start-build-runner # required to get output from the start-build-runner job
@@ -281,7 +326,28 @@ jobs:
           cd tests;
           pytest benchmarks --benchmark-json benchmarks/output.json
 
+      - name: Add commit metadata to benchmark results
+        run: |
+          # Add both commit hashes to the benchmark JSON for reference
+          python3 << 'EOF'
+          import json
+
+          with open('tests/benchmarks/output.json', 'r') as f:
+              data = json.load(f)
+
+          # Add metadata about both commits
+          if 'commit_info' not in data:
+              data['commit_info'] = {}
+
+          data['commit_info']['fvdb_core_commit'] = '${{ needs.get-fvdb-core-commit-hash.outputs.fvdb_core_commit_hash }}'
+          data['commit_info']['fvdb_reality_capture_commit'] = '${{ needs.get-fvdb-core-commit-hash.outputs.fvdb_reality_capture_commit_hash }}'
+
+          with open('tests/benchmarks/output.json', 'w') as f:
+              json.dump(data, f, indent=2)
+          EOF
+
       - name: Store benchmark result
+        id: store-benchmark
         uses: benchmark-action/github-action-benchmark@v1
         with:
             name: fvdb-reality-capture Benchmark with pytest-benchmark
@@ -294,12 +360,45 @@ jobs:
             comment-on-alert: true
             fail-on-alert: true
             alert-comment-cc-users: '@openvdb/fvdb-dev'
+            # Always comment on benchmark results, even without alerts
+            comment-always: true
+
+      - name: Save commit hashes for next run
+        if: steps.store-benchmark.outcome == 'success' || steps.store-benchmark.outcome == 'failure'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Check out gh-pages branch with token authentication
+          rm -rf gh-pages-repo
+          git clone --branch gh-pages https://x-access-token:${GITHUB_TOKEN}@github.com/${{ github.repository }}.git gh-pages-repo
+          cd gh-pages-repo
+
+          # Create directory if it doesn't exist
+          mkdir -p dev/bench
+
+          # Save current commit hashes for skip detection
+          cat > dev/bench/last_run_commits.txt << EOF
+          fvdb_core: ${{ needs.get-fvdb-core-commit-hash.outputs.fvdb_core_commit_hash }}
+          fvdb_reality_capture: ${{ needs.get-fvdb-core-commit-hash.outputs.fvdb_reality_capture_commit_hash }}
+          EOF
+
+          # Append to commit mapping log (for historical tracking)
+          echo "$(date -Iseconds) | fvdb-reality-capture: ${{ needs.get-fvdb-core-commit-hash.outputs.fvdb_reality_capture_commit_hash }} | fvdb-core: ${{ needs.get-fvdb-core-commit-hash.outputs.fvdb_core_commit_hash }}" >> dev/bench/commit_mapping.log
+
+          # Configure git
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+          # Commit and push
+          git add dev/bench/last_run_commits.txt dev/bench/commit_mapping.log
+          git commit -m "Save commit hashes for workflow run ${{ github.run_id }}" || echo "No changes to commit"
+          git push || { echo "Failed to push commit hashes. This may cause the next run to not skip properly."; exit 1; }
 
   ##############################################################################
   # STOP FVDB TESTS GPU RUNNER
   ##############################################################################
   fvdb-benchmarks-stop-gpu-runner:
-    if: ${{ always() && github.repository == 'openvdb/fvdb-reality-capture' }}
+    if: ${{ always() && github.repository == 'openvdb/fvdb-reality-capture' && needs.start-benchmarks-gpu-runner.result != 'skipped' }}
     name: Stop GPU EC2 runner for tests
     needs:
       - start-benchmarks-gpu-runner # required to get output from the start-benchmarks-gpu-runner job