Shortcut zero-size storeChunk calls without breaking collectivity

Author: franzpoeschel

include/openPMD/RecordComponent.tpp

@@ -115,14 +115,6 @@ RecordComponent::storeChunk(Offset o, Extent e, F &&createBuffer)
         IOHandler()->enqueue(IOTask(this, dCreate));
     }
 
-    if (size == 0)
-    {
-        // Don't forward this operation to the backend as it might create ugly
-        // zero-blocks in ADIOS2
-        setDirtyRecursive(true);
-        return DynamicMemoryView<T>();
-    }
-
     Parameter<Operation::GET_BUFFER_VIEW> getBufferView;
     getBufferView.offset = o;
     getBufferView.extent = e;
@@ -136,7 +128,10 @@ RecordComponent::storeChunk(Offset o, Extent e, F &&createBuffer)
         // type shared_ptr<T> or shared_ptr<T[]>
         auto data = std::forward<F>(createBuffer)(size);
         out.ptr = static_cast<void *>(data.get());
-        storeChunk(std::move(data), std::move(o), std::move(e));
+        if (size > 0)
+        {
+            storeChunk(std::move(data), std::move(o), std::move(e));
+        }
     }
     setDirtyRecursive(true);
     return DynamicMemoryView<T>{std::move(getBufferView), size, *this};

src/IO/ADIOS/ADIOS2IOHandler.cpp

@@ -1299,6 +1299,17 @@ void ADIOS2IOHandlerImpl::getBufferView(
     auto file = refreshFileFromParent(writable, /* preferParentFile = */ false);
     detail::ADIOS2File &ba = getFileData(file, IfFileNotOpen::ThrowError);
 
+    if (std::any_of(
+            parameters.extent.begin(), parameters.extent.end(), [](auto val) {
+                return val == 0;
+            }))
+    {
+        // Refuse empty operations, ADIOS2 creates ugly zero blocks for them,
+        // tell the frontend to do sth about it instead
+        parameters.out->backendManagedBuffer = false;
+        return;
+    }
+
     std::string name = nameOfVariable(writable);
     switch (m_useSpanBasedPutByDefault)
     {