Adding `Cumsum` operation (#322)

Unit testing the operation too.

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

@@ -348,6 +348,9 @@ namespace Tensorflow
         public static Tensor cast(Tensor x, TF_DataType dtype = TF_DataType.DtInvalid, string name = null) 
             => math_ops.cast(x, dtype, name);
 
+        public static Tensor cumsum(Tensor x, int axis = 0, bool exclusive = false, bool reverse = false, string name = null)
+            => math_ops.cumsum(x, axis: axis, exclusive: exclusive, reverse: reverse, name: name);
+
         public static Tensor argmax(Tensor input, int axis = -1, string name = null, int? dimension = null, TF_DataType output_type = TF_DataType.TF_INT64)
             => gen_math_ops.arg_max(input, axis, name: name, output_type: output_type);
 

src/TensorFlowNET.Core/Operations/gen_math_ops.cs

@@ -238,6 +238,13 @@ namespace Tensorflow
             return _op.outputs[0];
         }
 
+        public static Tensor cumsum(Tensor x, int axis = 0, bool exclusive = false, bool reverse = false, string name = null)
+        {
+            var _op = _op_def_lib._apply_op_helper("Cumsum", name, args: new { x, axis, exclusive, reverse });
+
+            return _op.outputs[0];
+        }
+
         /// <summary>
         /// Computes the sum along segments of a tensor.
         /// </summary>

src/TensorFlowNET.Core/Operations/math_ops.cs

@@ -80,6 +80,17 @@ namespace Tensorflow
             });
         }
 
+        public static Tensor cumsum(Tensor x, int axis = 0, bool exclusive = false, bool reverse = false, string name = null)
+        {
+            return with(ops.name_scope(name, "Cumsum", new {x}), scope =>
+            {
+                name = scope;
+                x = ops.convert_to_tensor(x, name: "x");
+
+                return gen_math_ops.cumsum(x, axis: axis, exclusive: exclusive, reverse: reverse, name: name);
+            });
+        }
+
         /// <summary>
         /// Computes Psi, the derivative of Lgamma (the log of the absolute value of
         /// `Gamma(x)`), element-wise.

test/TensorFlowNET.UnitTest/OperationsTest.cs

@@ -89,6 +89,47 @@ namespace TensorFlowNET.UnitTest
             }
         }
 
+        [TestMethod]
+        public void cumSumTest()
+        {
+            var a = tf.constant(new[] { 1, 1, 2, 3, 4, 5 });
+            var b = tf.cumsum(a);
+            var check = np.array(1, 2, 4, 7, 11, 16);
+
+            using (var sess = tf.Session())
+            {
+                var o = sess.run(b);
+                Assert.IsTrue(o.array_equal(check));
+            }
+
+            b = tf.cumsum(a, exclusive: true);
+            check = np.array(0, 1, 2, 4, 7, 11);
+
+            using (var sess = tf.Session())
+            {
+                var o = sess.run(b);
+                Assert.IsTrue(o.array_equal(check));
+            }
+
+            b = tf.cumsum(a, reverse: true);
+            check = np.array(16, 15, 14, 12, 9, 5);
+
+            using (var sess = tf.Session())
+            {
+                var o = sess.run(b);
+                Assert.IsTrue(o.array_equal(check));
+            }
+
+            b = tf.cumsum(a, exclusive:true, reverse: true);
+            check = np.array(15, 14, 12, 9, 5, 0);
+
+            using (var sess = tf.Session())
+            {
+                var o = sess.run(b);
+                Assert.IsTrue(o.array_equal(check));
+            }
+        }
+
         [TestMethod]
         public void addOpTests()
         {