reduction keep dim edge cases

Author: liqunfu

Source/CNTKv2LibraryDll/proto/onnx/CNTKToONNX.cpp

@@ -7070,21 +7070,27 @@ void CNTKToONNXHelper::SetReduceElementsAttributes(const FunctionPtr src, Node *
         reductionOpName = src->Attributes()[L"reductionOpName"].Value<wstring>();
     }
 
+    std::vector<Axis> reductionAxes;
+    if (src->Attributes().Contains(L"axisVec"))
+        reductionAxes = AsVector<Axis>(src->Attributes()[L"axisVec"].Value<std::vector<DictionaryValue>>());
+    else if (src->Attributes().Contains(L"axis"))
+        reductionAxes.push_back((Axis)(src->Attributes()[L"axis"].Value<Axis>()));
+
     //
     int64_t keepReducedDimensions = 0;
     if (src->Attributes().Contains(L"reductionKeepDimensions"))
         keepReducedDimensions = (int64_t)((bool)src->Attributes()[L"reductionKeepDimensions"].Value<bool>() ? 1 : 0);
-    else if (src->Inputs()[0].DynamicAxes().size() == src->Outputs()[0].DynamicAxes().size() &&
+    
+    // there are cases where reductionKeepDimensions attribute does not take effect.    
+    if((reductionAxes.size() == 1 && (reductionAxes[0] == Axis::DefaultBatchAxis() || reductionAxes[0] == Axis::AllStaticAxes() || reductionAxes[0] == Axis::AllAxes())))     // Reduction on batch axis in CNTK removes the batch axis, even if keepdims is true.
+        // For ONNX export we need to make sure we export keepdims as 0 (false).
+        // The same applies for AllStaticAxes.
+        keepReducedDimensions = 0;
+
+    if (src->Inputs()[0].DynamicAxes().size() == src->Outputs()[0].DynamicAxes().size() &&
         src->Inputs()[0].Shape().Rank() == src->Outputs()[0].Shape().Rank())
         keepReducedDimensions = 1;
 
-
-    std::vector<Axis> reductionAxes;
-    if (src->Attributes().Contains(L"axisVec"))
-        reductionAxes = AsVector<Axis>(src->Attributes()[L"axisVec"].Value<std::vector<DictionaryValue>>());
-    else if (src->Attributes().Contains(L"axis"))
-        reductionAxes.push_back((Axis)(src->Attributes()[L"axis"].Value<Axis>()));
-
     std::vector<int64_t> axes = ConvertAxesToOnnx(reductionAxes, src->Inputs()[0]);
 
     if (isSequenceReduceElement && axes.size() == 1 && axes[0] == 1 && src->Inputs()[0].DynamicAxes().size() == 1)