Add PersistentTape unit test.

src/TensorFlowNET.Core/APIs/tf.gradients.cs

@@ -1,5 +1,5 @@
 /*****************************************************************************
-   Copyright 2018 The TensorFlow.NET Authors. All Rights Reserved.
+   Copyright 2020 The TensorFlow.NET Authors. All Rights Reserved.
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
@@ -20,9 +20,15 @@ namespace Tensorflow
 {
     public partial class tensorflow
     {
+        /// <summary>
+        /// Record operations for automatic differentiation.
+        /// </summary>
+        /// <param name="persistent"></param>
+        /// <param name="watch_accessed_variables"></param>
+        /// <returns></returns>
         public GradientTape GradientTape(bool persistent = false,
-            bool watch_accessed_variables = true) 
-            => new GradientTape(persistent: persistent, 
+            bool watch_accessed_variables = true)
+            => new GradientTape(persistent: persistent,
                 watch_accessed_variables: watch_accessed_variables);
 
         public Tensor[] gradients(Tensor[] ys,

src/TensorFlowNET.Core/Eager/c_api.eager.cs

@@ -389,42 +389,6 @@ namespace Tensorflow
         [DllImport(TensorFlowLibName)]
         public static extern TFE_Executor TFE_ContextGetExecutorForThread(SafeContextHandle ctx);
 
-        /// <summary>
-        /// 
-        /// </summary>
-        /// <param name="ctx"></param>
-        /// <param name="device_name"></param>
-        /// <param name="op_name"></param>
-        /// <param name="name"></param>
-        /// <param name="args"></param>
-        /// <param name="input_size"></param>
-        /// <param name="set_op_attrs"></param>
-        /// <param name="status"></param>
-        /// <returns>EagerTensorHandle</returns>
-        [DllImport(TensorFlowLibName)]
-        public static extern SafeStatusHandle TFE_FastPathExecute(SafeContextHandle ctx, 
-            string device_name, 
-            string op_name,
-            string name,
-            IntPtr[] inputs,
-            int input_size,
-            string attrs_string,
-            TFE_FastPathExecute_SetOpAttrs set_op_attrs,
-            IntPtr[] outputs,
-            int output_size);
-        [UnmanagedFunctionPointer(CallingConvention.StdCall)]
-        public delegate void TFE_FastPathExecute_SetOpAttrs(IntPtr op);
-
-        [DllImport(TensorFlowLibName)]
-        public static extern SafeStatusHandle TFE_QuickExecute(SafeContextHandle ctx,
-            string device_name,
-            string op_name,
-            IntPtr[] inputs, 
-            int input_size,
-            TFE_FastPathExecute_SetOpAttrs set_op_attrs,
-            IntPtr[] outputs,
-            int output_size);
-
         [DllImport(TensorFlowLibName)]
         public static extern IntPtr TFE_TapeSetNew(bool persistent, bool watch_accessed_variables);
 

src/TensorFlowNET.Core/Gradients/GradientTape.cs

@@ -142,6 +142,14 @@ namespace Tensorflow.Gradients
             return results;
         }
 
+        /// <summary>
+        /// Temporarily stops recording operations on this tape.
+        /// </summary>
+        public void stop_recording()
+        {
+            _pop_tape();
+        }
+
         public void Dispose()
         {
             if (_recording)

src/TensorFlowNET.Core/Operations/array_ops.cs

@@ -328,7 +328,7 @@ namespace Tensorflow
             {
                 dtype = dtype.as_base_dtype();
                 name = scope;
-                var shape_tensor = constant_op._tensor_shape_tensor_conversion_function(shape);
+                
                 Tensor ones = null;
                 switch (dtype)
                 {
@@ -342,6 +342,11 @@ namespace Tensorflow
                         ones = constant(1);
                         break;
                 }
+
+                if (shape.ndim == 0)
+                    return ones;
+                
+                var shape_tensor = constant_op._tensor_shape_tensor_conversion_function(shape);
                 return fill(shape_tensor, ones, name: name);
             });
 

test/TensorFlowNET.UnitTest/NativeAPI/Eager/GradientEagerTest.cs

@@ -46,15 +46,15 @@ namespace TensorFlowNET.UnitTest.Gradient
             tape.watch(x);
             var y = tf.reduce_sum(x);
             var z = tf.multiply(y, y);
+            tape.Dispose();
+
             var dz_dx = tape.gradient(z, x);
 
             var expected = new float[] { 8.0f, 8.0f, 8.0f, 8.0f };
             Assert.IsTrue(Enumerable.SequenceEqual(dz_dx.ToArray<float>(), expected));
 
             var dz_dy = tape.gradient(z, y);
-
-            expected = new float[] { 8.0f, 8.0f, 8.0f, 8.0f };
-            Assert.IsTrue(Enumerable.SequenceEqual(dz_dx.ToArray<float>(), expected));
+            Assert.AreEqual((float)dz_dy, 8.0f);
         }
     }
 }