[GitHub] piiswrong commented on a change in pull request #11566: [MXNET-626] Add while_loop

[GitBox <gi...@apache.org>]

piiswrong commented on a change in pull request #11566: [MXNET-626] Add while_loop
URL: https://github.com/apache/incubator-mxnet/pull/11566#discussion_r201175882
 
 

 ##########
 File path: python/mxnet/ndarray/contrib.py
 ##########
 @@ -191,3 +191,128 @@ def check_input(inputs, in_type, msg):
     if not_data_list and len(outputs) == 1:
         outputs = outputs[0]
     return (outputs, states)
+
+
+def while_loop(loop_vars, cond, func, max_iterations):
+    """Run a while loop with user-defined computation and loop condition.
+
+    This operator simulates a while loop which iterately does customized computation
+    as long as the condition is satisfied.
+
+    `loop_vars` is a list of NDArrays on which the computation uses.
+
+    `cond` is a user-defined function as the loop condition.
+    It consumes `loop_vars`, and produces a scalar MXNet NDArray,
+    indicating the termination of the loop.
+    The loop ends when `cond` returns false (zero).
+    The `cond` is variadic, and its signature should be
+    `cond(*loop_vars) => NDArray`.
+
+    `func` is a user-defined function as the loop body.
+    It also consumes `loop_vars`, and produces `step_output` and `new_loop_vars` at each step.
+    The number of elements, shape, dtype of each element in `step_output` should be consistent.
 
 Review comment:
   what does consistent mean?

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