Rename WrittenChunkInfo.mpi_rank -> WrittenChunkInfo.sourceID (openPM…

…D#860)

include/openPMD/ChunkInfo.hpp

@@ -51,19 +51,23 @@ struct ChunkInfo
  * data producing application.
  * Produced by BaseRecordComponent::availableChunk.
  *
- * Carries along the usual chunk meta info also the rank from which
- * it was written.
- * If not specified explicitly, the rank will be assumed to be 0.
+ * Carries along the usual chunk meta info also the ID for the data source from
+ * which the chunk is received.
+ * Examples for this include the writing MPI rank in streaming setups or the
+ * subfile containing the chunk.
+ * If not specified explicitly, the sourceID will be assumed to be 0.
+ * This information will vary between different backends and should be used
+ * for optimization purposes only.
  */
 struct WrittenChunkInfo : ChunkInfo
 {
-    unsigned int mpi_rank = 0; //!< the MPI rank of the writing process
+    unsigned int sourceID = 0; //!< ID of the data source containing the chunk
 
+    explicit WrittenChunkInfo() = default;
     /*
      * If rank is smaller than zero, will be converted to zero.
      */
-    explicit WrittenChunkInfo() = default;
-    WrittenChunkInfo( Offset, Extent, int mpi_rank );
+    WrittenChunkInfo( Offset, Extent, int sourceID );
     WrittenChunkInfo( Offset, Extent );
 
     bool

src/ChunkInfo.cpp

@@ -36,9 +36,9 @@ ChunkInfo::operator==( ChunkInfo const & other ) const
 WrittenChunkInfo::WrittenChunkInfo(
     Offset offset_in,
     Extent extent_in,
-    int mpi_rank_in )
+    int sourceID_in )
     : ChunkInfo( std::move( offset_in ), std::move( extent_in ) )
-    , mpi_rank( mpi_rank_in < 0 ? 0 : mpi_rank_in )
+    , sourceID( sourceID_in < 0 ? 0 : sourceID_in )
 {
 }
 
@@ -50,7 +50,7 @@ WrittenChunkInfo::WrittenChunkInfo( Offset offset_in, Extent extent_in )
 bool
 WrittenChunkInfo::operator==( WrittenChunkInfo const & other ) const
 {
-    return this->mpi_rank == other.mpi_rank &&
+    return this->sourceID == other.sourceID &&
         this->ChunkInfo::operator==( other );
 }
 } // namespace openPMD

src/IO/JSON/JSONIOHandlerImpl.cpp

@@ -366,7 +366,7 @@ namespace openPMD
                         e.push_back( entry );
                     }
                     res.emplace_back(
-                        std::move( o ), std::move( e ), chunk.mpi_rank );
+                        std::move( o ), std::move( e ), chunk.sourceID );
                 }
             }
             return res;

src/binding/python/ChunkInfo.cpp

@@ -55,7 +55,7 @@ void init_Chunk(py::module &m) {
         )
         .def_readwrite("offset",   &WrittenChunkInfo::offset   )
         .def_readwrite("extent",   &WrittenChunkInfo::extent   )
-        .def_readwrite("mpi_rank", &WrittenChunkInfo::mpi_rank )
+        .def_readwrite("source_id", &WrittenChunkInfo::sourceID )
     ;
 }
 

test/ParallelIOTest.cpp

@@ -343,9 +343,9 @@ available_chunks_test( std::string file_ending )
         {
             REQUIRE(
                 chunk.offset ==
-                Offset{ static_cast< unsigned >( chunk.mpi_rank ), 0 } );
+                Offset{ static_cast< unsigned >( chunk.sourceID ), 0 } );
             REQUIRE( chunk.extent == Extent{ 1, 4 } );
-            ranks.emplace_back( chunk.mpi_rank );
+            ranks.emplace_back( chunk.sourceID );
         }
         std::sort( ranks.begin(), ranks.end() );
         for( size_t i = 0; i < ranks.size(); ++i )

test/python/unittest/API/APITest.py

@@ -1609,6 +1609,8 @@ def makeAvailableChunksRoundTrip(self, ext):
 
         chunks = read.iterations[0].meshes["E"]["x"].available_chunks()
         chunks = sorted(chunks, key=lambda chunk: chunk.offset)
+        for chunk in chunks:
+            self.assertEqual(chunk.source_id, 0)
         # print("EXTENSION:", ext)
         # for chunk in chunks:
         #     print("{} -- {}".format(chunk.offset, chunk.extent))