implement math_ops.real, reduce_variance, reduce_std

* implement math_ops.real, reduce_variance, reduce_std

* add dtype.real_dtype()

* add outward-facing api functions

src/TensorFlowNET.Core/APIs/tf.math.cs

@@ -422,6 +422,9 @@ namespace Tensorflow
         public Tensor range(object start, object limit = null, object delta = null, TF_DataType dtype = TF_DataType.DtInvalid, string name = "range")
             => math_ops.range(start, limit: limit, delta: delta, dtype: dtype, name: name);
 
+        public Tensor real(Tensor input, string name = null)
+            => math_ops.real(input, name);
+       
         /// <summary>
         /// Computes the "logical or" of elements across dimensions of a tensor.
         /// </summary>
@@ -509,6 +512,12 @@ namespace Tensorflow
         public Tensor reduce_min(Tensor input_tensor, int[] axis = null, bool keepdims = false, string name = null)
             => math_ops.reduce_min(input_tensor, axis, keepdims, name);
 
+        public Tensor reduce_std(Tensor input_tensor, int[] axis = null, bool keepdims = false, string name = null)
+            => math_ops.reduce_std(input_tensor, axis, keepdims, name);
+
+        public Tensor reduce_variance(Tensor input_tensor, int[] axis = null, bool keepdims = false, string name = null)
+            => math_ops.reduce_variance(input_tensor, axis, keepdims, name);
+       
         public Tensor sigmoid<T>(T x, string name = null)
             => math_ops.sigmoid(x, name: name);
 

src/TensorFlowNET.Core/Operations/math_ops.cs

@@ -229,6 +229,22 @@ namespace Tensorflow
 
         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 real(Tensor input, string name = null)
+        {
+            using (var name_ = ops.name_scope(name, "Real", new [] {input}))
+            {
+                input = ops.convert_to_tensor(input, name: "input");
+                if (input.dtype.is_complex())
+                {
+                    var real_dtype = input.dtype.real_dtype();
+                    return real(input, name: name);
+                } else
+                {
+                    return input;
+                }
+            }
+        }
 
         /// <summary>
         /// Computes the mean of elements across dimensions of a tensor.
@@ -295,6 +311,46 @@ namespace Tensorflow
             }
         }
 
+        public static Tensor reduce_std(Tensor input_tensor, int[] axis = null, bool keepdims = false, string name = null)
+        {
+            if (name == null)
+                name = "reduce_std";
+            // else {name = name;}
+
+            using (ops.name_scope(name))
+            {
+                var variance = reduce_variance(input_tensor, axis: axis, keepdims: keepdims);
+                return gen_math_ops.sqrt(variance);
+            }
+        }
+       
+        public static Tensor reduce_variance(Tensor input_tensor, int[] axis = null, bool keepdims = false, string name = null)
+        {
+            if (name == null)
+                name = "reduce_variance";
+            // else {name = name;}
+
+            using (ops.name_scope(name))
+            {
+                var means = reduce_mean(input_tensor, axis: axis, keepdims: true);
+                if (means.dtype.is_integer())
+                    throw new TypeError("Input must be either real or complex");
+                var diff = input_tensor - means;
+                
+                Tensor squared_deviations;
+                if (diff.dtype.is_complex())
+                {
+                    var real_dtype = diff.dtype.real_dtype();
+                    squared_deviations = real(
+                        gen_math_ops.mul(conj(diff), diff));
+                } else
+                {
+                    squared_deviations = gen_math_ops.square(diff);
+                }
+                return reduce_mean(squared_deviations, axis: axis, keepdims: keepdims);
+            }
+        }
+
         public static Tensor sigmoid<T>(T x, string name = null)
             => tf_with(ops.name_scope(name, "Sigmoid", x), scope =>
             {

src/TensorFlowNET.Core/Tensors/dtypes.cs

@@ -278,5 +278,16 @@ namespace Tensorflow
         {
             return self.as_datatype_enum() == other.as_datatype_enum();
         }
+       
+        public static TF_DataType real_dtype(this TF_DataType self)
+        {
+            TF_DataType base_ = self.as_base_dtype();
+            if (base_ == complex64)
+                return float32;
+            else if (base_ == complex128)
+                return float64;
+            else
+                return self;
+        }
     }
 }