Fix gradient of squared_difference SciSharp#787

Oceania2018 · Oceania2018 · commit f55650d9e181 · 2021-03-27T20:02:40.000-05:00
diff --git a/src/TensorFlowNET.Core/Gradients/nn_grad.cs b/src/TensorFlowNET.Core/Gradients/nn_grad.cs
@@ -122,13 +122,14 @@ public static Tensor[] _SparseSoftmaxCrossEntropyWithLogitsGrad(Operation op, Te
         [RegisterGradient("SquaredDifference")]
         public static Tensor[] _SquaredDifferenceGrad(Operation op, Tensor[] grads)
         {
-           //"""Returns the gradient for (x-y)^2."""
             Tensor x = op.inputs[0];
             Tensor y = op.inputs[1];
+            var scale = ops.convert_to_tensor(2.0f, dtype: x.dtype);
+            var x_grad = math_ops.scalar_mul(scale, grads[0]) * (x - y);
             return new Tensor[]
             {
-                x,
-                y
+                x_grad,
+                -x_grad
             };
         }
         /// <summary>
diff --git a/src/TensorFlowNET.Core/Operations/math_ops.cs b/src/TensorFlowNET.Core/Operations/math_ops.cs
@@ -272,6 +272,9 @@ public static Tensor not_equal<Tx, Ty>(Tx x, Ty y, string name = null)
         public static Tensor mul_no_nan<Tx, Ty>(Tx x, Ty y, string name = null)
             => gen_math_ops.mul_no_nan(x, y, name: name);
 
+        public static Tensor scalar_mul<Tscale, Tx>(Tscale scale, Tx x, string name = null)
+            => tf.Context.ExecuteOp("Mul", name, new ExecuteOpArgs(scale, x));
+
         public static Tensor real(Tensor input, string name = null)
         {
             return tf_with(ops.name_scope(name, "Real", new[] { input }), scope =>
diff --git a/src/TensorFlowNET.Core/tensorflow.cs b/src/TensorFlowNET.Core/tensorflow.cs
@@ -48,7 +48,7 @@ public partial class tensorflow : ITensorFlowObject
         public tensorflow()
         {
             Logger = new LoggerConfiguration()
-                .MinimumLevel.Error()
+                .MinimumLevel.Debug()
                 .WriteTo.Console()
                 .CreateLogger();
 
diff --git a/test/TensorFlowNET.UnitTest/GradientTest/GradientEagerTest.cs b/test/TensorFlowNET.UnitTest/GradientTest/GradientEagerTest.cs
@@ -25,7 +25,6 @@ public void ConstantSquare()
             Assert.AreEqual((float)grad, 3.0f);
         }
 
-        [Ignore]
         [TestMethod]
         public void SquaredDifference_Constant()
         {

Original file line number	Diff line number	Diff line change
`@@ -122,13 +122,14 @@ public static Tensor[] _SparseSoftmaxCrossEntropyWithLogitsGrad(Operation op, Te`
`122`	`122`	`[RegisterGradient("SquaredDifference")]`
`123`	`123`	`public static Tensor[] _SquaredDifferenceGrad(Operation op, Tensor[] grads)`
`124`	`124`	`{`
`125`		`- //"""Returns the gradient for (x-y)^2."""`
`126`	`125`	`Tensor x = op.inputs[0];`
`127`	`126`	`Tensor y = op.inputs[1];`
	`127`	`+ var scale = ops.convert_to_tensor(2.0f, dtype: x.dtype);`
	`128`	`+ var x_grad = math_ops.scalar_mul(scale, grads[0]) * (x - y);`
`128`	`129`	`return new Tensor[]`
`129`	`130`	`{`
`130`		`- x,`
`131`		`- y`
	`131`	`+ x_grad,`
	`132`	`+ -x_grad`
`132`	`133`	`};`
`133`	`134`	`}`
`134`	`135`	`/// <summary>`
Original file line number	Diff line number	Diff line change
`@@ -272,6 +272,9 @@ public static Tensor not_equal<Tx, Ty>(Tx x, Ty y, string name = null)`
`272`	`272`	`public static Tensor mul_no_nan<Tx, Ty>(Tx x, Ty y, string name = null)`
`273`	`273`	`=> gen_math_ops.mul_no_nan(x, y, name: name);`
`274`	`274`
	`275`	`+ public static Tensor scalar_mul<Tscale, Tx>(Tscale scale, Tx x, string name = null)`
	`276`	`+ => tf.Context.ExecuteOp("Mul", name, new ExecuteOpArgs(scale, x));`
	`277`	`+`
`275`	`278`	`public static Tensor real(Tensor input, string name = null)`
`276`	`279`	`{`
`277`	`280`	`return tf_with(ops.name_scope(name, "Real", new[] { input }), scope =>`
Original file line number	Diff line number	Diff line change
`@@ -48,7 +48,7 @@ public partial class tensorflow : ITensorFlowObject`
`48`	`48`	`public tensorflow()`
`49`	`49`	`{`
`50`	`50`	`Logger = new LoggerConfiguration()`
`51`		`- .MinimumLevel.Error()`
	`51`	`+ .MinimumLevel.Debug()`
`52`	`52`	`.WriteTo.Console()`
`53`	`53`	`.CreateLogger();`
`54`	`54`
Original file line number	Diff line number	Diff line change
`@@ -25,7 +25,6 @@ public void ConstantSquare()`
`25`	`25`	`Assert.AreEqual((float)grad, 3.0f);`
`26`	`26`	`}`
`27`	`27`
`28`		`- [Ignore]`
`29`	`28`	`[TestMethod]`
`30`	`29`	`public void SquaredDifference_Constant()`
`31`	`30`	`{`