Added MNIST loader.

Author: interesaaat

Test/TorchSharp.cs

@@ -1,4 +1,5 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System.Linq;
 using TorchSharp.Tensor;
 
 namespace TorchSharp.Test
@@ -316,5 +317,17 @@ public void TestTrainingAdam()
                 optimizer.Step();
             }
         }
+
+        [TestMethod]
+        public void TestMNISTLoader()
+        {
+            var train = Data.Loader.MNIST(@"E:/Source/Repos/LibTorchSharp/MNIST", 64);
+
+            foreach (var (data, target) in train.Take(10))
+            {
+                CollectionAssert.AreEqual(data.Shape, new long[] { 64, 1, 28, 28 });
+                CollectionAssert.AreEqual(target.Shape, new long[] { 64 });
+            }
+        }
     }
 }

TorchSharp/Data/Loader.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
+using TorchSharp.Tensor;
+
+namespace TorchSharp.Data
+{
+    public class Loader
+    {
+        [DllImport("LibTorchSharp")]
+        extern static void Data_LoaderMNIST(
+            string filename, 
+            long batchSize, 
+            bool isTrain,
+            AllocatePinnedArray dataAllocator, 
+            AllocatePinnedArray targetAllocator);
+
+        static public IEnumerable<(ITorchTensor<float> data, ITorchTensor<float> target)> MNIST(string filename, long batchSize, bool isTrain = true)
+        {
+            IntPtr[] dataPtrArray;
+            IntPtr[] targetPtrArray;
+
+            using (var data = new PinnedArray<IntPtr>())
+            using (var target = new PinnedArray<IntPtr>())
+            {
+                Data_LoaderMNIST(filename, batchSize, isTrain, data.CreateArray, target.CreateArray);
+                dataPtrArray = data.Array;
+                targetPtrArray = target.Array;
+            }
+
+            return dataPtrArray
+                .Zip(
+                    targetPtrArray, 
+                    (d, t) => (
+                        (ITorchTensor<float>)new FloatTensor(new FloatTensor.HType(d, true)), 
+                        (ITorchTensor<float>)new FloatTensor(new FloatTensor.HType(t, true))));
+        }
+    }
+}

TorchSharp/NN/Module.cs

@@ -111,14 +111,14 @@ public virtual void ZeroGrad()
 
         public virtual IEnumerable<ITorchTensor<float>> Parameters()
         {
-            IntPtr[] ros;
+            IntPtr[] ptrArray;
 
             using (var pa = new PinnedArray<IntPtr>())
             {
                 NN_GetParameters(handle, pa.CreateArray);
-                ros = pa.Array;
+                ptrArray = pa.Array;
             }
-            return ros.Select(x => new FloatTensor(new FloatTensor.HType(x, true)));
+            return ptrArray.Select(x => new FloatTensor(new FloatTensor.HType(x, true)));
         }
 
         [DllImport("LibTorchSharp")]