Add concatenate in dataset.

Author: Oceania2018

src/TensorFlowNET.Core/Data/ConcatenateDataset.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Tensorflow.Framework;
+using Tensorflow.Framework.Models;
+using static Tensorflow.Binding;
+
+namespace Tensorflow.Data
+{
+    /// <summary>
+    /// A `Dataset` that concatenates its input with given dataset.
+    /// </summary>
+    public class ConcatenateDataset : DatasetV2
+    {
+        IDatasetV2 _input_dataset;
+        IDatasetV2 _dataset_to_concatenate;
+        public ConcatenateDataset(IDatasetV2 input_dataset, IDatasetV2 dataset_to_concatenate)
+        {
+            _input_dataset = input_dataset;
+            _dataset_to_concatenate = dataset_to_concatenate;
+            var _structure = new List<TensorSpec>();
+            foreach(var (i, spec) in enumerate(dataset_to_concatenate.element_spec))
+            {
+                var shape = _input_dataset.output_shapes[i].most_specific_compatible_shape(spec.shape);
+                _structure.Add(new TensorSpec(shape, dtype: spec.dtype));
+            }
+            structure = _structure.ToArray();
+
+            variant_tensor = ops.concatenate_dataset(input_dataset.variant_tensor, 
+                    dataset_to_concatenate.variant_tensor,
+                    output_types, output_shapes);
+        }
+    }
+}

src/TensorFlowNET.Core/Data/DatasetV2.cs

@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using Tensorflow.Data;
 using Tensorflow.Framework.Models;
 using static Tensorflow.Binding;
 
@@ -26,6 +27,9 @@ public class DatasetV2 : IDatasetV2
         public IDatasetV2 cache(string filename = "")
             => new CacheDataset(this, filename: filename);
 
+        public IDatasetV2 concatenate(IDatasetV2 dataset)
+            => new ConcatenateDataset(this, dataset);
+
         public IDatasetV2 take(int count = -1)
             => new TakeDataset(this, count: count);
 

src/TensorFlowNET.Core/Data/IDatasetV2.cs

@@ -23,6 +23,13 @@ public interface IDatasetV2 : IEnumerable<(Tensor, Tensor)>
         /// <returns></returns>
         IDatasetV2 cache(string filename = "");
 
+        /// <summary>
+        /// Creates a `Dataset` by concatenating the given dataset with this dataset.
+        /// </summary>
+        /// <param name="dataset"></param>
+        /// <returns></returns>
+        IDatasetV2 concatenate(IDatasetV2 dataset);
+
         /// <summary>
         /// 
         /// </summary>

src/TensorFlowNET.Core/Data/OwnedIterator.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Linq;
 using Tensorflow.Framework.Models;
+using static Tensorflow.Binding;
 
 namespace Tensorflow
 {
@@ -36,7 +38,10 @@ public Tensor[] next()
         {
             try
             {
-                return ops.iterator_get_next(_iterator_resource, _dataset.output_types, _dataset.output_shapes);
+                var results = ops.iterator_get_next(_iterator_resource, _dataset.output_types, _dataset.output_shapes);
+                foreach(var (i, tensor) in enumerate(results))
+                    tensor.set_shape(_element_spec[i].shape);
+                return results;
             }
             catch (OutOfRangeError ex)
             {