Support DisposableNamedOnnxValue inputs in c# Run()

csharp/src/Microsoft.ML.OnnxRuntime/DisposableNamedOnnxValue.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using Microsoft.ML.OnnxRuntime.Tensors;
 using System.Runtime.InteropServices;
@@ -60,13 +61,48 @@ public void Dispose()
 
     public class DisposableNamedOnnxValue : NamedOnnxValue, IDisposable
     {
-        protected IDisposable _nativeMemoryManager;
-        protected DisposableNamedOnnxValue(string name, Object value, IDisposable nativeMemoryManager)
+        private NativeMemoryHandler _nativeMemoryManager;
+        private DisposableNamedOnnxValue(string name, Object value, NativeMemoryHandler nativeMemoryManager)
             : base(name, value)
         {
             _nativeMemoryManager = nativeMemoryManager;
         }
 
+        /// <summary>
+        /// Overrides the base class method. Since the instance already has access to the 
+        /// underlying OrtValue handle (if this instance hasn't been disposed), it just assigns
+        /// that to the output onnxValue. With respect to pinnedMemoryHandle, it has no operation
+        /// to do, as this class doesn't maintain a managed buffer. It doesn't have to maintain it
+        /// as it already is associated with the object of interest (native OrtValue)
+        /// </summary>
+        /// <param name="onnxValue"></param>
+        /// <param name="pinnedMemoryHandle"></param>
+        /// <param name="disposeOnnxValueAfterUse"></param>
+        internal override void ToNativeOnnxValue(out IntPtr onnxValue, 
+                                                 out MemoryHandle pinnedMemoryHandle)
+        {
+            // Make sure that this instance hasn't been disposed yet
+            if (disposedValue)
+            {
+                throw new ObjectDisposedException(nameof(DisposableNamedOnnxValue),
+                                                  "This instance of DisposableNamedOnnxValue has already been disposed");
+            }
+
+            // If not already disposed, _nativeMemoryManager can only be null
+            // for Maps and SequenceTensors
+            if (_nativeMemoryManager == null)
+            {
+                throw new NotSupportedException("Use of Maps and SequenceTensors is not yet supported");
+            }
+
+            // Assign the onnxValue by querying this instance's NativeOnnxTensorMemory instance
+            onnxValue = _nativeMemoryManager.Handle;
+
+            // PinnedMemoryHandle holds the default value as DisposableNamedOnnxValue
+            // doesn't hold any managed buffer (that needs to be pinned)
+            pinnedMemoryHandle = default;
+        }
+
         internal static DisposableNamedOnnxValue CreateTensorFromOnnxValue(string name, IntPtr nativeOnnxValue)
         {
             DisposableNamedOnnxValue result = null;

csharp/src/Microsoft.ML.OnnxRuntime/InferenceSession.cs

@@ -143,7 +143,8 @@ public IDisposableReadOnlyCollection<DisposableNamedOnnxValue> Run(IReadOnlyColl
                 inputNames[inputIndex] = input.Name;
 
                 // create Tensor from the input if feasible, else throw notsupported exception for now
-                input.ToNativeOnnxValue(out inputTensors[inputIndex], out pinnedBufferHandles[inputIndex]);
+                input.ToNativeOnnxValue(out inputTensors[inputIndex], 
+                                        out pinnedBufferHandles[inputIndex]);
 
                 inputIndex++;
             }
@@ -187,12 +188,19 @@ public IDisposableReadOnlyCollection<DisposableNamedOnnxValue> Run(IReadOnlyColl
             }
             finally
             {
-                // always unpin the input buffers, and delete the native Onnx value objects
-                for (int i = 0; i < inputs.Count; i++)
+                inputIndex = 0;
+                foreach (var input in inputs)
                 {
-                    NativeMethods.OrtReleaseValue(inputTensors[i]); // For elementary type Tensors, this should not release the buffer, but should delete the native tensor object.
-                                                                    // For string tensors, this releases the native memory allocated for the tensor, including the buffer
-                    pinnedBufferHandles[i].Dispose();
+                    // For NamedOnnxValue, always unpin the input buffers, and delete the native Onnx value objects
+                    // For DisposableNamedOnnxValue, the user needs to do this by invoking Dispose
+                    if (input.GetType() == typeof(NamedOnnxValue))
+                    {
+                        NativeMethods.OrtReleaseValue(inputTensors[inputIndex]); // For elementary type Tensors, this should not release the buffer, but should delete the native tensor object.
+                                                                                 // For string tensors, this releases the native memory allocated for the tensor, including the buffer
+                        pinnedBufferHandles[inputIndex].Dispose();
+                    }
+
+                    inputIndex++;
                 }
             }
 
@@ -429,7 +437,7 @@ internal static NodeMetadata GetMetadataFromTypeInfo(IntPtr typeInfo)
             }
             if (valueType != OnnxValueType.ONNX_TYPE_TENSOR && valueType != OnnxValueType.ONNX_TYPE_SPARSETENSOR)
             {
-                return new NodeMetadata(valueType, new int[] { }, new string[] { },  typeof(NamedOnnxValue));
+                return new NodeMetadata(valueType, new int[] { }, new string[] { }, typeof(NamedOnnxValue));
             }
 
             IntPtr tensorInfo;
@@ -467,7 +475,7 @@ internal static NodeMetadata GetMetadataFromTypeInfo(IntPtr typeInfo)
             {
                 symbolicDimensions[i] = Marshal.PtrToStringAnsi(dimensionNamePtrs[i]); //assumes charset = ANSI
             }
-          
+
             return new NodeMetadata(valueType, intDimensions, symbolicDimensions, dotnetType);
         }
 

csharp/src/Microsoft.ML.OnnxRuntime/NamedOnnxValue.cs

@@ -28,7 +28,7 @@ public static NamedOnnxValue CreateFromTensor<T>(string name, Tensor<T> value)
             return new NamedOnnxValue(name, value);
         }
 
-        public string Name { get { return _name; } }
+        public string Name { get { return _name; } set { _name = value; } }
 
         /// <summary>
         /// Try-get value as a Tensor&lt;T&gt;.
@@ -71,7 +71,9 @@ public IDictionary<K, V> AsDictionary<K, V>()
         /// </summary>
         /// <param name="onnxValue"></param>
         /// <param name="pinnedMemoryHandle"></param>
-        internal void ToNativeOnnxValue(out IntPtr onnxValue, out MemoryHandle pinnedMemoryHandle)
+        /// <param name="disposeOnnxValueAfterUse"></param>
+        internal virtual void ToNativeOnnxValue(out IntPtr onnxValue, 
+                                                out MemoryHandle pinnedMemoryHandle)
         {
             //try to cast _value to Tensor<T>
             TensorElementType nativeElementType = TensorElementType.DataTypeMax; //invalid

csharp/src/Microsoft.ML.OnnxRuntime/NativeOnnxTensorMemory.cs

@@ -12,7 +12,15 @@
 
 namespace Microsoft.ML.OnnxRuntime
 {
-    internal class NativeOnnxTensorMemory<T> : MemoryManager<T>
+    /// <summary>
+    /// A non-public interface detailing the contract to be honored by NativeOnnxTensorMemory
+    /// </summary>
+    internal interface NativeMemoryHandler : IDisposable
+    {
+        IntPtr Handle { get;}
+    }
+
+    internal class NativeOnnxTensorMemory<T> : MemoryManager<T>, NativeMemoryHandler 
     {
         private bool _disposed;
         private int _referenceCount;
@@ -122,6 +130,8 @@ public NativeOnnxTensorMemory(IntPtr onnxValueHandle)
             }
         }
 
+        public IntPtr Handle { get { return _onnxValueHandle; } }
+
         ~NativeOnnxTensorMemory()
         {
             Dispose(false);

csharp/test/Microsoft.ML.OnnxRuntime.Tests/InferenceTest.cs

@@ -731,6 +731,100 @@ private void TestModelInputBOOL()
             }
         }
 
+        [Fact]
+        private void TestReusingRunOutputNonStringType()
+        {
+            // model takes 1x5 input of fixed type, echoes back
+            string modelPath = Path.Combine(Directory.GetCurrentDirectory(), "test_types_BOOL.pb");
+            using (var session = new InferenceSession(modelPath))
+            {
+                var container = new List<NamedOnnxValue>();
+                var tensorIn = new DenseTensor<bool>(new bool[] { true, false, true, false, true }, new int[] { 1, 5 });
+                var nov = NamedOnnxValue.CreateFromTensor("input", tensorIn);
+                container.Add(nov);
+                var res1 = session.Run(container);
+
+                // change the name of the DisposableNamedOnnxValue
+                res1.First().Name = "input";
+
+                // Run inferencing 2 times using the output of the first Run()
+                for(int i=0; i<2; ++i)
+                { 
+                    using (var res2 = session.Run(res1))
+                    {
+                        var tensorOut = res2.First().AsTensor<bool>();
+                        Assert.True(tensorOut.SequenceEqual(tensorIn));
+                    }
+                }
+            }
+        }
+
+        [Fact]
+        private void TestReusingRunOutputStringType()
+        {
+            // model takes 1x5 input of fixed type, echoes back
+            string modelPath = Path.Combine(Directory.GetCurrentDirectory(), "test_types_STRING.pb");
+            using (var session = new InferenceSession(modelPath))
+            {
+                var container = new List<NamedOnnxValue>();
+                var tensorIn = new DenseTensor<string>(new string[] { "a", "b", "c", "d", "e" }, new int[] { 1, 5 });
+                var nov = NamedOnnxValue.CreateFromTensor("input", tensorIn);
+                container.Add(nov);
+                var res1 = session.Run(container);
+
+                // change the name of the DisposableNamedOnnxValue
+                res1.First().Name = "input";
+
+                // Run inferencing 2 times using the output of the first Run()
+                for (int i = 0; i < 2; ++i)
+                {
+                    using (var res2 = session.Run(res1))
+                    {
+                        var tensorOut = res2.First().AsTensor<string>();
+                        Assert.True(tensorOut.SequenceEqual(tensorIn));
+                    }
+                }
+            }
+        }
+
+        [Fact]
+        private void TestReusingDisposedRunOutput()
+        {
+            // model takes 1x5 input of fixed type, echoes back
+            string modelPath = Path.Combine(Directory.GetCurrentDirectory(), "test_types_BOOL.pb");
+            using (var session = new InferenceSession(modelPath))
+            {
+                var container = new List<NamedOnnxValue>();
+                var tensorIn = new DenseTensor<bool>(new bool[] { true, false, true, false, true }, new int[] { 1, 5 });
+                var nov = NamedOnnxValue.CreateFromTensor("input", tensorIn);
+                container.Add(nov);
+                var res1 = session.Run(container);
+
+                // Dispose the result tensor
+                res1.First().Dispose();
+
+                bool succeeded = false;
+
+                // Now try using the disposed output as input to another Run()
+                try
+                {
+                    // Run() should fail with a user friendly error message.
+                    session.Run(res1);
+                }
+
+                catch (ObjectDisposedException e)
+                {
+                    var errorString = "This instance of DisposableNamedOnnxValue has already been disposed";
+
+                    Assert.True(e.Message.Contains(errorString));
+
+                    succeeded = true;
+                }
+
+                Assert.True(succeeded);
+            }
+        }
+
         [Fact]
         private void TestModelInputINT32()
         {