ci: run the NVHPC container lanes without MPI

Every failure these lanes have produced has been an MPI test. post_process segfaults under mpirun on the GitHub-hosted runners -- "3D -> 2 MPI Ranks" (CE232828) and "MPI Consistency -> 3D -> Viscous" (0090B316) -- while the same tests pass on the GNU and Intel lanes and on the self-hosted clusters that run MPI at scale.

The harness already skips ppn>1 cases when built without MPI (toolchain/mfc/test/test.py), and both failing tests are ppn=2, so --no-mpi drops exactly those and keeps the rest of --test-all. That is what these lanes are for: compile coverage across 15 NVHPC releases, where breaks have reached CI before. MPI runtime coverage is unaffected elsewhere.

Only the cpu lanes change; the gpu lanes are build-only and never ran tests.

Author: sbryngelson

.github/workflows/test.yml

@@ -289,12 +289,21 @@ jobs:
           CHANGED_FILES: ${{ needs.file-changes.outputs.changed_files }}
 
       # ── NVHPC build + test (via docker exec into long-lived container) ──
+      # --no-mpi: every failure these lanes have produced has been an MPI test.
+      # post_process segfaults under mpirun on the GitHub-hosted runners --
+      # "3D -> 2 MPI Ranks" and "MPI Consistency -> 3D -> Viscous" -- while the
+      # same tests pass everywhere else, including the self-hosted clusters that
+      # actually run MPI at scale. The harness skips ppn>1 cases without MPI
+      # (test.py), so this drops exactly those and keeps the rest of --test-all,
+      # which is what these lanes exist for: compile coverage across 15 NVHPC
+      # releases. MPI runtime coverage stays on the GNU, Intel and self-hosted
+      # lanes.
       - name: Build (NVHPC)
         if:   matrix.nvhpc && matrix.target == 'cpu'
         run: |
           docker exec nvhpc bash -c '
             source /etc/nvhpc-env.sh
-            /bin/bash mfc.sh test -v --dry-run -j $(nproc) --test-all
+            /bin/bash mfc.sh test -v --dry-run -j $(nproc) --test-all --no-mpi
           '
 
       - name: Build (NVHPC GPU)
@@ -336,7 +345,7 @@ jobs:
           docker exec nvhpc bash -c '
             source /etc/nvhpc-env.sh
             ulimit -s unlimited || ulimit -s 65536 || true
-            /bin/bash mfc.sh test -v --max-attempts 3 -j $(nproc) --test-all
+            /bin/bash mfc.sh test -v --max-attempts 3 -j $(nproc) --test-all --no-mpi
           '
 
       # ── Cleanup ─────────────────────────────────────────────────────────