extra_ops.py 文件源码

def grad(self, inp, cost_grad):
        """
        Notes
        -----
        The gradient is currently implemented for matrices only.
        """
        a, val, offset = inp
        grad = cost_grad[0]
        height, width = grad.shape

        if (a.dtype.startswith('complex')):
            return [None, None]

        # only valid for matrices
        wr_a = fill_diagonal_offset(grad, 0, offset)

        offset_abs = basic.abs_(offset)
        pos_offset_flag = basic.ge(offset, 0)
        neg_offset_flag = basic.lt(offset, 0)
        min_wh = basic.minimum(width, height)

        start = offset * pos_offset_flag + offset_abs * width * neg_offset_flag
        num_of_step = basic.minimum(min_wh, width * pos_offset_flag +
                                    height * neg_offset_flag - offset_abs)

        step = a.shape[1] + 1
        end = start + step * num_of_step

        # input of slice should be integer
        start = basic.cast(start, 'int32')
        step = basic.cast(step, 'int32')
        end = basic.cast(end, 'int32')

        wr_val = grad.flatten()[start:end:step].sum()

        wr_offset = theano.gradient.grad_undefined(
            self, 2, offset,
            "offset is not defined for non-integer offset so"
            " fill_diagonal_offset(a,val,offset+eps) is undefined")

        return [wr_a, wr_val, wr_offset]