add disposetensor in dataset

Author: yueyinqiu

src/TorchSharp/DataLoader.cs

@@ -352,6 +352,10 @@ public bool MoveNext()
                             Current = collate_fn(items, device);
                         }
 
+                        foreach (var item in items) {
+                            dataset.DisposeTensor(item);
+                        }
+
                         return true;
 
                         void ProcessPendingBatches()

src/TorchSharp/Dataset.cs

@@ -15,13 +15,25 @@ public static partial class data
                 /// </summary>
                 public abstract class Dataset : Dataset<Dictionary<string, torch.Tensor>>
                 {
+                    public override void DisposeTensor(Dictionary<string, Tensor> tensor)
+                    {
+                        foreach (var t in tensor.Values) {
+                            t.Dispose();
+                        }
+                    }
                 }
 
                 /// <summary>
                 /// Iterable-style data sets
                 /// </summary>
                 public abstract class IterableDataset : Dataset<IList<Tensor>>
                 {
+                    public override void DisposeTensor(IList<Tensor> tensor)
+                    {
+                        foreach (var t in tensor) {
+                            t.Dispose();
+                        }
+                    }
                 }
 
                 /// <summary>
@@ -47,6 +59,8 @@ public void Dispose()
                     /// <returns>Tensors of index. DataLoader will catenate these tensors into batches.</returns>
                     public abstract T GetTensor(long index);
 
+                    public abstract void DisposeTensor(T tensor);
+
                     protected virtual void Dispose(bool disposing)
                     {
                     }

src/TorchSharp/Utils/TensorDataset.cs

@@ -37,7 +37,7 @@ internal TensorDataset(torch.Tensor[] tensors)
                 long size1 = tensors[0].shape[0];
                 if (!tensors.All(t => t.shape[0] == size1)) throw new ArgumentException("All tensors must have the same first dimension size.", nameof(tensors));
 
-                _tensors.AddRange(tensors);
+                _tensors = tensors.Select(x => x.alias()).ToArray();
             }
 
             /// <summary>
@@ -62,8 +62,16 @@ public override long Count {
                 return this[index];
             }
 
-            private List<torch.Tensor> _tensors = new List<torch.Tensor>();
-        }
+            private torch.Tensor[] _tensors;
 
+            protected override void Dispose(bool disposing)
+            {
+                if (disposing) {
+                    foreach (var tensor in _tensors) {
+                        tensor.Dispose();
+                    }
+                }
+            }
+        }
     }
 }