[GitHub] ArmageddonKnight opened a new issue #13312: Forward/BackwardResource in OperatorProperty Interface

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ArmageddonKnight opened a new issue #13312: Forward/BackwardResource in OperatorProperty Interface
URL: https://github.com/apache/incubator-mxnet/issues/13312
 
 
   Hi,
   
   Sorry but I have a question regarding the `OperatorProperty` interface. Let us take the `RNNProp` as an example:
   
   ```C++
   class RNNProp : public OperatorProperty
   {
     ...
     std::vector<ResourceRequest> ForwardResource(
         const std::vector<TShape> &in_shape) const override {
       return {ResourceRequest::kTempSpace};
     }
   
     std::vector<ResourceRequest> BackwardResource(
         const std::vector<TShape> &in_shape) const override {
       return {ResourceRequest::kTempSpace};
     }
     ...
   ```
   
   I noticed we do not declare ahead of time the shape or the size of temporary workspace that we need. It was not until the actual forward/backward propagation when we say:
   
   ```C++
       Tensor<gpu, 1, DType> temp_space =
         ctx.requested[rnn_enum::kTempSpace].get_space_typed<gpu, 1, DType>(
                                 mshadow::Shape1(temp_size), s);
   ```
   
   I have two questions regarding the temporary workspace management:
   
   - Am I right in saying that **the length of the vector returned by the `ForwardResource` and `BackwardResource` method is equal to the number of temporary workspace tensors I can use in the forward and backward propagation, respectively?**
   - **Why don't the `ForwardResource` and `BackwardResource` return a list of _shapes_ that indicate the shapes of the workspace**? IMHO this information can be helpful in managing the workspace (allocation/deallocation/reuse) ahead of time.

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