From 37ec089dd91097b651033d615b1dfc508e8c2bc2 Mon Sep 17 00:00:00 2001
From: Willem Deconinck <willem.deconinck@ecmwf.int>
Date: Tue, 12 Sep 2023 19:20:45 +0200
Subject: [PATCH] Use mpi_comm in DelaunayMeshGenerator

---
 .../meshgenerator/detail/DelaunayMeshGenerator.cc  | 10 ++++++++--
 .../meshgenerator/detail/DelaunayMeshGenerator.h   |  1 +
 src/tests/mesh/test_meshgen_splitcomm.cc           | 14 +++++++++++++-
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.cc b/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.cc
index f8a3b0a2e..4ab849ba0 100644
--- a/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.cc
+++ b/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.cc
@@ -42,7 +42,8 @@ namespace meshgenerator {
 DelaunayMeshGenerator::DelaunayMeshGenerator() = default;
 
 DelaunayMeshGenerator::DelaunayMeshGenerator(const eckit::Parametrisation& p) {
-    p.get("part",part_=mpi::rank());
+    p.get("mpi_comm",mpi_comm_=mpi::comm().name());
+    p.get("part",part_=mpi::comm(mpi_comm_).rank());
     p.get("reshuffle",reshuffle_=true);
     p.get("remove_duplicate_points",remove_duplicate_points_=true);
 }
@@ -57,6 +58,8 @@ void DelaunayMeshGenerator::hash(eckit::Hash& h) const {
 
 void DelaunayMeshGenerator::generate(const Grid& grid, const grid::Distribution& dist, Mesh& mesh) const {
  
+    mpi::Scope mpi_scope(mpi_comm_);
+
     auto build_global_mesh = [&](Mesh& mesh) {
         idx_t nb_nodes = grid.size();
         mesh.nodes().resize(nb_nodes);
@@ -102,6 +105,7 @@ void DelaunayMeshGenerator::generate(const Grid& grid, const grid::Distribution&
     if( dist.nb_partitions() == 1 ) {
         build_global_mesh(mesh);
         setGrid(mesh, grid, dist.type());
+        mesh.metadata().set("mpi_comm",mpi_comm_);
         return;
     }
 
@@ -357,10 +361,12 @@ void DelaunayMeshGenerator::generate(const Grid& grid, const grid::Distribution&
     extract_mesh_partition(global_mesh, mesh);
 
     setGrid(mesh, grid, dist.type());
+    mesh.metadata().set("mpi_comm",mpi_comm_);
 }
 
 void DelaunayMeshGenerator::generate(const Grid& g, Mesh& mesh) const {
-    generate( g, grid::Distribution{g}, mesh);
+    mpi::Scope mpi_scope(mpi_comm_);
+    generate( g, grid::Distribution{g,g.partitioner()}, mesh);
 }
 
 namespace {
diff --git a/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.h b/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.h
index f397e6408..ef9c981c6 100644
--- a/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.h
+++ b/src/atlas/meshgenerator/detail/DelaunayMeshGenerator.h
@@ -39,6 +39,7 @@ class DelaunayMeshGenerator : public MeshGenerator::Implementation {
     virtual void generate(const Grid&, const grid::Distribution&, Mesh&) const override;
     virtual void generate(const Grid&, Mesh&) const override;
 
+    std::string mpi_comm_;
     int part_;
     bool remove_duplicate_points_;
     bool reshuffle_;
diff --git a/src/tests/mesh/test_meshgen_splitcomm.cc b/src/tests/mesh/test_meshgen_splitcomm.cc
index 544aafe2f..97b31771f 100644
--- a/src/tests/mesh/test_meshgen_splitcomm.cc
+++ b/src/tests/mesh/test_meshgen_splitcomm.cc
@@ -98,6 +98,19 @@ CASE("StructuredMeshGenerator") {
     mesh.polygon().outputPythonScript(grid().name()+"_polygons_1.py");
 }
 
+CASE("DelaunayMeshGenerator") {
+    Fixture fixture;
+
+    MeshGenerator meshgen{"delaunay", option::mpi_comm("split")};
+    Mesh mesh = meshgen.generate(grid_CS());
+    EXPECT_EQUAL(mesh.nb_parts(),mpi::comm("split").size());
+    EXPECT_EQUAL(mesh.part(),mpi::comm("split").rank());
+    EXPECT_EQUAL(mesh.mpi_comm(),"split");
+    EXPECT_EQUAL(mpi::comm().name(),"world");
+    output::Gmsh gmsh(grid_CS().name()+"_delaunay.msh",util::Config("coordinates","xyz"));
+    gmsh.write(mesh);
+}
+
 CASE("CubedSphereDualMeshGenerator") {
     Fixture fixture;
 
@@ -177,7 +190,6 @@ CASE("MatchingPartitioner") {
 }
 
 
-
 }  // namespace test
 }  // namespace atlas