Added the batch_dot22 function.

theano/tensor/basic.py

@@ -4325,6 +4325,23 @@ def set_subtensor(x, y, inplace=False,
     return inc_subtensor(x, y, inplace, set_instead_of_inc=True,
             tolerate_inplace_aliasing=tolerate_inplace_aliasing)
 
+def batched_dot22(x, y):
+    """
+    :param x: A 3D Tensor with sizes (dim1, dim2, dim3)
+    :param y: A 3D Tensor with sizes (dim1, dim2, dim4)
+    This function computes the dot product between the two 3D tensors, by iterating
+    over the first dimension using scan.
+    Returns a 3D tensor of size (dim1, dim3, dim4)
+    Example:
+    >>> first = T.tensor3('first')
+    >>> second = T.tensor3('second')
+    >>> result = batched_dot22(first, second)
+    """
+    result, updates = theano.scan(fn=lambda x_mat, y_mat: T.dot(x_mat.T, y_mat),
+            outputs_info=None,
+            sequences=[x_mat, y_mat],
+            non_sequences=None)
+    return result
 
 def inc_subtensor(x, y, inplace=False, set_instead_of_inc=False,
         tolerate_inplace_aliasing=False):