[GitHub] jeremiedb commented on issue #10928: Optimizers memory usage

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jeremiedb commented on issue #10928: Optimizers memory usage
URL: https://github.com/apache/incubator-mxnet/issues/10928#issuecomment-396429822
 
 
   As an additional pointer, the issue seems tied to R's NDArray being set to read only after an initial mutation. https://github.com/apache/incubator-mxnet/blob/master/R-package/src/ndarray.h#L86 @tqchen ? 
   
   Basic comparative example between R and Python: 
   
   R: 
   ```
   > state <- mx.nd.array(c(1,2,3,3))
   > grad <- mx.nd.array(1:4)
   > weight <- mx.nd.array(1:4)
   > mx.nd.sgd.mom.update(weight, grad, state, lr = 0.1, momentum = 0.5, out = weight)
   [1] 1.4 2.8 4.2 5.1
   > mx.nd.sgd.mom.update(weight, grad, state, lr = 0.1, momentum = 0.5, out = weight)
   Error in mx.nd.sgd.mom.update(weight, grad, state, lr = 0.1, momentum = 0.5,  : 
     ./ndarray.h:87: RCheck failed: ptr_->writable && !ptr_->moved Passing a read only NDArray to mutate function
   
   ```
   
   Python:
   
   ```
   state  = mx.nd.array([1, 2, 3, 3])
   grad  = mx.nd.array([1,2,3,4])
   weight = mx.nd.array([1,2,3,4])
   print(nd.sgd_mom_update(weight, grad, state, momentum = 0.5, lr=0.1, out=weight))
   print(nd.sgd_mom_update(weight, grad, state, momentum = 0.5, lr=0.1, out=weight))
   
   [1.4 2.8 4.2 5.1]
   <NDArray 4 @cpu(0)>
   
   [1.5  3.   4.5  5.25]
   <NDArray 4 @cpu(0)>
   ```

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