theano_backend.py 文件源码

def pool2d(x, pool_size, strides=(1, 1), padding='valid',
           data_format=None, pool_mode='max'):
    if data_format is None:
        data_format = image_data_format()
    if data_format not in {'channels_first', 'channels_last'}:
        raise ValueError('Unknown data_format:', data_format)

    assert pool_size[0] >= 1 and pool_size[1] >= 1

    if padding == 'same':
        w_pad = pool_size[0] - 2 if pool_size[0] > 2 and pool_size[0] % 2 == 1 else pool_size[0] - 1
        h_pad = pool_size[1] - 2 if pool_size[1] > 2 and pool_size[1] % 2 == 1 else pool_size[1] - 1
        pad = (w_pad, h_pad)
    elif padding == 'valid':
        pad = (0, 0)
    else:
        raise ValueError('Invalid border mode:', padding)

    if data_format not in {'channels_first', 'channels_last'}:
        raise ValueError('Unknown data_format:', data_format)

    if data_format == 'channels_last':
        x = x.dimshuffle((0, 3, 1, 2))

    if pool_mode == 'max':
        pool_out = pool.pool_2d(x, ws=pool_size, stride=strides,
                                ignore_border=True,
                                pad=pad,
                                mode='max')
    elif pool_mode == 'avg':
        pool_out = pool.pool_2d(x, ws=pool_size, stride=strides,
                                ignore_border=True,
                                pad=pad,
                                mode='average_exc_pad')
    else:
        raise ValueError('Invalid pooling mode:', pool_mode)
    if padding == '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 data_format == 'channels_last':
        pool_out = pool_out.dimshuffle((0, 2, 3, 1))
    return pool_out