Add ConcreteFunction to support dataset map.

src/TensorFlowNET.Core/Data/DatasetV2.cs

@@ -52,7 +52,7 @@ namespace Tensorflow
 
         public IDatasetV2 map(Func<Tensor, Tensor> map_func,
             bool use_inter_op_parallelism = true,
-            bool preserve_cardinality = false,
+            bool preserve_cardinality = true,
             bool use_legacy_function = false)
             => new MapDataset(this, 
                 map_func,

src/TensorFlowNET.Core/Data/MapDataset.cs

@@ -1,6 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text;
+using Tensorflow.Functions;
+using Tensorflow.Graphs;
+using static Tensorflow.Binding;
 
 namespace Tensorflow
 {
@@ -15,12 +19,10 @@ namespace Tensorflow
             bool preserve_cardinality = false,
             bool use_legacy_function = false) : base(input_dataset)
         {
-            foreach(var input in input_dataset)
-            {
-                var data = map_func(input.Item1);
-            }
+            var func = new ConcreteFunction(map_func, input_dataset.element_spec[0].dtype);
 
             variant_tensor = ops.map_dataset(input_dataset.variant_tensor,
+                func,
                 output_types,
                 output_shapes);
         }

src/TensorFlowNET.Core/Eager/EagerRunner.TFE_FastPathExecute.cs

@@ -6,6 +6,7 @@ using static Tensorflow.Binding;
 using Tensorflow.Util;
 using System.Runtime.InteropServices;
 using Tensorflow.Contexts;
+using Tensorflow.Functions;
 
 namespace Tensorflow.Eager
 {
@@ -385,7 +386,10 @@ namespace Tensorflow.Eager
                     status.Check(true);
                     break;
                 case TF_AttrType.TF_ATTR_FUNC:
-                    c_api.TFE_OpSetAttrFunctionName(op, key, value.ToString(), value.ToString().Length);
+                    if (value is ConcreteFunction func)
+                        c_api.TFE_OpSetAttrFunctionName(op, key, func.Name, func.Name.Length);
+                    else
+                        throw new NotImplementedException("TF_AttrType.TF_ATTR_FUNC"); 
                     break;
                 default:
                     throw new NotImplementedException($"SetOpAttrScalar for {type}");

src/TensorFlowNET.Core/Functions/ConcreteFunction.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Tensorflow.Graphs;
+using static Tensorflow.Binding;
+
+namespace Tensorflow.Functions
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    public class ConcreteFunction : IDisposable
+    {
+        public string Name => _handle == IntPtr.Zero ? string.Empty : c_api.StringPiece(c_api.TF_FunctionName(_handle));
+        IntPtr _handle;
+
+        public ConcreteFunction(Func<Tensor, Tensor> func, TF_DataType dtype)
+        {
+            string func_name = $"autograph_{Guid.NewGuid()}_{func.Method.Name}";
+
+            tf.compat.v1.disable_eager_execution();
+
+            // IntPtr func_handle;
+            using (var graph = new FuncGraph(func_name))
+            {
+                graph.as_default();
+                var input = tf.placeholder(dtype);
+                var output = func(input);
+
+                var opers = graph._nodes_by_name.Values.Select(x => x as Operation).ToArray();
+                _handle = graph.ToGraph(opers,
+                    new Operation[] { input },
+                    new Operation[] { output },
+                    null);
+
+                c_api.TFE_ContextAddFunction(tf.Context.Handle, _handle, tf.Status.Handle);
+            }
+
+            tf.enable_eager_execution();
+        }
+
+        public Tensor Execute(Tensor arg)
+        {
+            var result = tf.Runner.TFE_Execute(tf.Context,
+                tf.Context.DeviceName,
+                Name,
+                new[] { arg },
+                null,
+                1);
+            return result[0];
+        }
+
+        public void Dispose()
+        {
+            c_api.TFE_ContextRemoveFunction(tf.Context.Handle, Name, tf.Status.Handle);
+        }
+    }
+}

src/TensorFlowNET.Core/Functions/c_api.function.cs

@@ -21,6 +21,9 @@ namespace Tensorflow
 {
     public partial class c_api
     {
+        [DllImport(TensorFlowLibName)]
+        public static extern void TF_DeleteFunction(IntPtr handle);
+
         /// <summary>
         /// Write out a serialized representation of `func` (as a FunctionDef protocol
         /// message) to `output_func_def` (allocated by TF_NewBuffer()).

src/TensorFlowNET.Core/Graphs/FuncGraph.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Text;
+using Tensorflow.Functions;
 using static Tensorflow.Binding;
 
 namespace Tensorflow.Graphs

src/TensorFlowNET.Core/Operations/dataset_ops.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Text;
 using Tensorflow.Framework.Models;
+using Tensorflow.Functions;
 using static Tensorflow.Binding;
 
 namespace Tensorflow
@@ -419,7 +420,7 @@ namespace Tensorflow
         /// <param name="iterator"></param>
         /// <param name="name"></param>
         /// <returns></returns>
-        public Tensor map_dataset(Tensor dataset, TF_DataType[] output_types, TensorShape[] output_shapes, 
+        public Tensor map_dataset(Tensor dataset, ConcreteFunction f, TF_DataType[] output_types, TensorShape[] output_shapes, 
             bool use_inter_op_parallelism = true, bool preserve_cardinality = false, string name = null)
         {
             if (tf.Context.executing_eagerly())
@@ -428,7 +429,7 @@ namespace Tensorflow
                     "MapDataset", name,
                     null,
                     dataset, new Tensor[0],
-                    "f", "MapDataset",
+                    "f", f,
                     "output_types", output_types, 
                     "output_shapes", output_shapes,
                     "use_inter_op_parallelism", use_inter_op_parallelism,

test/TensorFlowNET.UnitTest/Dataset/DatasetTest.cs

@@ -118,17 +118,17 @@ namespace TensorFlowNET.UnitTest.Dataset
             }
         }
 
-        [TestMethod, Ignore]
+        [TestMethod]
         public void Map()
         {
             long value = 0;
 
-            var dataset = tf.data.Dataset.range(3);
-            var dataset1 = dataset.map(x => x);
+            var dataset = tf.data.Dataset.range(0, 2);
+            dataset = dataset.map(x => x + 10);
 
             foreach (var item in dataset)
             {
-                Assert.AreEqual(value, (long)item.Item1);
+                Assert.AreEqual(value + 10, (long)item.Item1);
                 value++;
             }
         }

test/TensorFlowNET.UnitTest/NativeAPI/c_test_util.cs

@@ -2,6 +2,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using Tensorflow;
+using Tensorflow.Functions;
 using Tensorflow.Util;
 using Buffer = Tensorflow.Buffer;