shared_ptr<IMASGD<ElemType>> _GetBlockMomentumSGD(const MPIWrapperPtr& mpi, size_t traceLevel, DEVICEID_TYPE devID, bool useNesterovBlockMomentum, bool resetSGDMomentum, double blockLearningRate, double blockMomentumAsTimeConstant, size_t modelAggregationBlockSize)
