test: working example of halo exchange

This test includes two examples for different grid layouts:

- 3 x 1 grid (3 procs)
- 2 x 2 grid (4 procs)

Makes use of the Slice functionality

Author: TomMelt

CMakeLists.txt

@@ -37,6 +37,7 @@ else()
         set(NSDG_NetCDF_Library "netcdf-cxx4")
     else()
         set(NSDG_NetCDF_Library "netcdf_c++4")
+        set(NSDG_NetCDF_Library "netcdf-cxx4")
     endif()
 endif()
 target_include_directories(nextsimlib PUBLIC "${netCDF_INCLUDE_DIR}")

core/src/include/ModelArraySlice.hpp

@@ -100,11 +100,11 @@ class ModelArraySlice {
     }
 
     ModelArray& copyToModelArray(ModelArray& target) const;
-    template <typename T> T& copyToBuffer(T& buffer)
+    template <typename T> T& copyToBuffer(T& buffer, size_t startIndex = 0)
     {
         // make no especial attempt at efficiency here
         SliceIter thisIter(slice, data.dimensions());
-        auto biter = buffer.begin();
+        auto biter = std::next(buffer.begin(), startIndex);
 
         while (!thisIter.isEnd()) {
             // If the buffer ends before the slice, throw an exception

core/src/include/Slice.hpp

@@ -142,7 +142,18 @@ class Slice {
         }
         std::ostream& print(std::ostream& os) const
         {
-            return os << start << ":" << stop << ":" << step;
+            // TODO remove me before merging into develop
+            // this is for debugging purposes only
+            if (start.isAll()) {
+                os << ":*:";
+            } else {
+                os << start << ":";
+            }
+            if (stop.isAll()) {
+                return os << "*:" << step;
+            } else {
+                return os << stop << ":" << step;
+            }
         }
         friend SliceIter;
     };

core/test/CMakeLists.txt

@@ -77,6 +77,28 @@ if(ENABLE_MPI)
     )
     target_link_libraries(testModelMetadata_MPI3 PRIVATE nextsimlib doctest::doctest)
 
+    # set(ModelArrayStructure "discontinuousgalerkin")
+    set(CoreDir "../../core/src/")
+
+    # set(MODEL_INCLUDE_DIR "./testmodelarraydetails")
+    add_executable(testHaloExchange_MPI4
+      "HaloExchange_test.cpp"
+      "MainMPI.cpp"
+      "../src/ModelArray.cpp"
+      "../src/ModelArraySlice.cpp"
+      "${MODEL_INCLUDE_DIR}/ModelArrayDetails.cpp"
+      )
+    target_compile_definitions(testHaloExchange_MPI4 PRIVATE USE_MPI)
+    target_include_directories(
+        testHaloExchange_MPI4 PRIVATE
+        "../src"
+        "../../dynamics/src"
+        ${MODEL_INCLUDE_DIR}
+    )
+    target_link_libraries(testHaloExchange_MPI4 PRIVATE doctest::doctest Eigen3::Eigen)
+
+    set(MODEL_INCLUDE_DIR "../../core/src/discontinuousgalerkin")
+
     add_executable(testParaGrid_MPI2 "ParaGrid_test.cpp" "MainMPI.cpp")
     target_compile_definitions(
         testParaGrid_MPI2