add splice unittest

contrib/Python/cntk/ops/tests/reshaping_test.py

@@ -80,8 +80,6 @@ def test_op_slice(input_data, slice_params, expected_result, device_id, precisio
     # The second for batch of one sample.
 
     a = I([input_data])
-    def op_slice(x, beg_index, end_index, axis):
-        return x[beg_index:end_index]
 
     def _ax_slices(x, beg_index, end_index, axis):
         '''
@@ -232,6 +230,51 @@ def test_op_slice_overload(device_id, precision):
         result = a[1,object(),2]
 
 
+SPLICE_TEST_CASES = [
+    #(input_data1, input_data2, axis, expected_result)
+    ([1], [2], 0, [1,2]),
+    ([[1,2],[4,5]], [[10,20],[30, 40],[50, 60]], 0, [[1, 2],[4, 5],[10, 20],[30, 40],[50, 60]]),
+    ([[1,2],[4,5]], [[10,20,30],[40, 50, 60]], 1, [[1,2,10,20,30],[4,5,40,50,60]]),
+    ([[[1,2],[3,4]],[[5,6],[7,8]]], [[10,20],[30,40]], 0, [[[1,2],[3,4]],[[5,6],[7,8]],[[10,20],[30,40]]]),    
+]
+@pytest.mark.parametrize("input_data1, input_data2, axis, expected_result", SPLICE_TEST_CASES)
+def test_op_splice(input_data1, input_data2, axis, expected_result, device_id, precision):
+    # Forward pass test
+    #==================
+    # We compute the expected output for the forward pass.
+    # We need two surrounding brackets:
+    # The first for sequences (length=1, since we have dynamic_axis='').
+    # The second for batch of one sample.
+
+    a = I([input_data1])
+    b = I([input_data2])
+    
+    def op_splice(x, y, axis):
+        return np.concatenate((x,y), axis)
+
+    # splice using the operator
+    result = C.splice((a, b), axis)
+
+    unittest_helper(result, None, [[expected_result]], device_id=device_id, 
+                precision=precision, clean_up=True, backward_pass=False)
+
+    # Backward pass test
+    # ==================
+    # The gradient of the splice operator is all ones in the shape of the input
+
+    def grad_slice(x):
+        return np.ones_like(x)
+
+    expected_gradient1 = grad_slice(np.asarray(input_data1))
+    expected_gradient2 = grad_slice(np.asarray(input_data2))
+    
+    unittest_helper(result, None, [[expected_gradient1]], device_id = device_id,
+                    precision=precision, clean_up=True, backward_pass=True, input_node=a)
+
+    unittest_helper(result, None, [[expected_gradient2]], device_id = device_id,
+                    precision=precision, clean_up=True, backward_pass=True, input_node=b)
+
+
 TRANSPOSE_DIMS_TEST_CASES = [
     #(input_shape, axis1, axis2, expected_output_shape)
     ([2, 3],     0, 1, [3, 2]),