From 874b8d2e5dca269909622ba5f87b4a1e0a90e4a0 Mon Sep 17 00:00:00 2001
From: mloubout <mathias.louboutin@gmail.com>
Date: Mon, 4 Aug 2025 09:43:11 -0400
Subject: [PATCH 1/2] mpi: prevent crashes with single rank

---
 devito/builtins/arithmetic.py | 36 ++++++++---------------------------
 devito/data/data.py           |  2 +-
 2 files changed, 9 insertions(+), 29 deletions(-)

diff --git a/devito/builtins/arithmetic.py b/devito/builtins/arithmetic.py
index 5e807219f5..a4d6d0c687 100644
--- a/devito/builtins/arithmetic.py
+++ b/devito/builtins/arithmetic.py
@@ -180,33 +180,13 @@ def inner(f, g):
     return f.dtype(n.data[0])
 
 
-@dv.switchconfig(log_level='ERROR')
-@check_builtins_args
-def mmin(f):
-    """
-    Retrieve the minimum.
-
-    Parameters
-    ----------
-    f : array_like or Function
-        Input operand.
-    """
-    if isinstance(f, dv.Constant):
-        return f.data
-    elif isinstance(f, dv.types.dense.DiscreteFunction):
-        v = np.min(f.data_ro_domain)
-        if f.grid is None or not dv.configuration['mpi']:
-            return v.item()
-        else:
-            comm = f.grid.distributor.comm
-            return comm.allreduce(v, dv.mpi.MPI.MIN).item()
-    else:
-        raise ValueError("Expected Function, got `%s`" % type(f))
+mmin = lambda f: _reduce_func(f, np.min, dv.mpi.MPI.MIN)
+mmax = lambda f: _reduce_func(f, np.max, dv.mpi.MPI.MAX)
 
 
 @dv.switchconfig(log_level='ERROR')
 @check_builtins_args
-def mmax(f):
+def _reduce_func(f, func, mfunc):
     """
     Retrieve the maximum.
 
@@ -218,11 +198,11 @@ def mmax(f):
     if isinstance(f, dv.Constant):
         return f.data
     elif isinstance(f, dv.types.dense.DiscreteFunction):
-        v = np.max(f.data_ro_domain)
-        if f.grid is None or not dv.configuration['mpi']:
-            return v.item()
-        else:
+        v = func(f.data_ro_domain)
+        if f.data._is_decomposed:
             comm = f.grid.distributor.comm
-            return comm.allreduce(v, dv.mpi.MPI.MAX).item()
+            return comm.allreduce(v, mfunc).item()
+        else:
+            return v.item()
     else:
         raise ValueError("Expected Function, got `%s`" % type(f))
diff --git a/devito/data/data.py b/devito/data/data.py
index 90d2570c47..c09fb79a9f 100644
--- a/devito/data/data.py
+++ b/devito/data/data.py
@@ -197,7 +197,7 @@ def wrapper(data, *args, **kwargs):
     @property
     def _is_decomposed(self):
         return self._is_distributed and configuration['mpi'] and \
-            self._distributor.comm.size > 1
+            self._distributor.is_parallel
 
     def __repr__(self):
         return super(Data, self._local).__repr__()

From 442e4d258c374689e5431c522af340bd89e5538e Mon Sep 17 00:00:00 2001
From: mloubout <mathias.louboutin@gmail.com>
Date: Mon, 4 Aug 2025 10:34:44 -0400
Subject: [PATCH 2/2] CI: make sure docker use branch name to avoid conflicts

---
 .github/workflows/pytest-gpu.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/pytest-gpu.yml b/.github/workflows/pytest-gpu.yml
index 49719994b1..0ace06a2e2 100644
--- a/.github/workflows/pytest-gpu.yml
+++ b/.github/workflows/pytest-gpu.yml
@@ -77,7 +77,7 @@ jobs:
       - name: Set per-runner tags
         run: |
           echo "DOCKER_IMAGE=${{ matrix.name }}-${RUNNER_NAME// /_}" >> $GITHUB_ENV
-          echo "CONTAINER_BASENAME=testrun-${{ matrix.name }}-${RUNNER_NAME// /_}" >> $GITHUB_ENV
+          echo "CONTAINER_BASENAME=testrun-${{ matrix.name }}-${RUNNER_NAME// /_}-${{ github.sha }}" >> $GITHUB_ENV
 
       - name: Ensure buildx builder
         run: |