theano_backend.py 文件源码

def pool2d(x, pool_size, strides=(1, 1), border_mode='valid',
           dim_ordering='th', pool_mode='max'):
    if border_mode == 'same':
        w_pad = pool_size[0] - 2 if pool_size[0] % 2 == 1 else pool_size[0] - 1
        h_pad = pool_size[1] - 2 if pool_size[1] % 2 == 1 else pool_size[1] - 1
        padding = (w_pad, h_pad)
    elif border_mode == 'valid':
        padding = (0, 0)
    else:
        raise Exception('Invalid border mode: ' + str(border_mode))

    if dim_ordering not in {'th', 'tf'}:
        raise Exception('Unknown dim_ordering ' + str(dim_ordering))

    if dim_ordering == 'tf':
        x = x.dimshuffle((0, 3, 1, 2))

    if pool_mode == 'max':
        pool_out = pool.pool_2d(x, ds=pool_size, st=strides,
                                ignore_border=True,
                                padding=padding,
                                mode='max')
    elif pool_mode == 'avg':
        pool_out = pool.pool_2d(x, ds=pool_size, st=strides,
                                ignore_border=True,
                                padding=padding,
                                mode='average_exc_pad')
    else:
        raise Exception('Invalid pooling mode: ' + str(pool_mode))

    if border_mode == 'same':
        expected_width = (x.shape[2] + strides[0] - 1) // strides[0]
        expected_height = (x.shape[3] + strides[1] - 1) // strides[1]

        pool_out = pool_out[:, :,
                            : expected_width,
                            : expected_height]

    if dim_ordering == 'tf':
        pool_out = pool_out.dimshuffle((0, 2, 3, 1))
    return pool_out