ControlFlowState.PostProcessing

src/TensorFlowNET.Core/Operations/ControlFlows/ControlFlowState.cs

@@ -290,7 +290,35 @@ namespace Tensorflow.Operations.ControlFlows
 
         public void PostProcessing()
         {
-            throw new NotImplementedException("PostProcessing");
+            foreach(var grad_state in _map.Values)
+            {
+                foreach(var b_merge in grad_state.switch_map.Values)
+                {
+                    if(b_merge.op.inputs[0] == b_merge.op.inputs[1])
+                    {
+                        Tensor next_grad_val = null;
+                        // The value of this loop variable at iteration i+1 doesn't
+                        // depend on its value at iteration i. So use zeros as the
+                        // gradients for all iterations > 0.
+                        var dtype = b_merge.op.inputs[0].dtype;
+                        var shape = b_merge.op.inputs[0].TensorShape;
+                        if (shape.is_fully_defined())
+                        {
+                            grad_state.grad_context.Enter();
+                            // Create a zeros and use it for iterations > 0.
+                            var grad_val = constant_op.constant(0, dtype: dtype, shape: shape);
+                            next_grad_val = control_flow_ops._NextIteration(grad_val);
+                            grad_state.grad_context.Exit();
+                        }
+                        else
+                        {
+                            throw new NotImplementedException("PostProcessing shape is not fully defined.");
+                        }
+
+                        b_merge.op._update_input(1, next_grad_val);
+                    }
+                }
+            }
         }
     }
 }