# Copyright (c) Facebook, Inc. and its affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.
from contextlib import contextmanager

from torch._C._functorch import _vmap_add_layers, _vmap_remove_layers

_enabled = False


@contextmanager
def _enable_layers(dims):
    global _enabled
    assert not _enabled
    input = sorted((d._level, d.size) for d in dims if not isinstance(d, int))
    n = len(input)
    try:
        _vmap_add_layers(input)
        _enabled = True
        yield
    finally:
        _enabled = False
        _vmap_remove_layers(n)
