def pool2d(x, pool_size, strides=(1, 1),
           border_mode='valid', dim_ordering='th', pool_mode='max'):
    if border_mode == 'same':
        padding = 'SAME'
    elif border_mode == 'valid':
        padding = 'VALID'
    else:
        raise Exception('Invalid border mode: ' + str(border_mode))

    strides = (1,) + strides + (1,)
    pool_size = (1,) + pool_size + (1,)

    if _FLOATX == 'float64':
        # tf max_pool only supports float32
        x = tf.cast(x, 'float32')

    if dim_ordering in {'tf', 'th'}:
        if dim_ordering == 'th':
            # TF uses the last dimension as channel dimension,
            # instead of the 2nd one.
            # TH input shape: (samples, input_depth, rows, cols)
            # TF input shape: (samples, rows, cols, input_depth)
            # TH kernel shape: (depth, input_depth, rows, cols)
            # TF kernel shape: (rows, cols, input_depth, depth)
            x = tf.transpose(x, (0, 2, 3, 1))
        if pool_mode == 'max':
            x = tf.nn.max_pool(x, pool_size, strides, padding=padding)
        elif pool_mode == 'avg':
            x = tf.nn.avg_pool(x, pool_size, strides, padding=padding)
        else:
            raise Exception('Invalid pooling mode: ' + str(pool_mode))
        if dim_ordering == 'th':
            x = tf.transpose(x, (0, 3, 1, 2))
    else:
        raise Exception('Unknown dim_ordering: ' + str(dim_ordering))

    if _FLOATX == 'float64':
        x = tf.cast(x, 'float64')
    return x


# RANDOMNESS
2D Pooling.
dataset/ETHPy150Open fchollet/keras/keras/backend/tensorflow_backend.py/pool2d