Prepare for multi-framework support in NAS (#4976)

docs/source/reference/others.rst

 Uncategorized Modules
 =====================
 
+nni.common.framework
+--------------------
+
+.. automodule:: nni.common.framework
+    :members:
+
 nni.common.serializer
 ---------------------
 

nni/__init__.py

@@ -9,6 +9,7 @@ except ModuleNotFoundError:
 from .runtime.log import _init_logger
 _init_logger()
 
+from .common.framework import *
 from .common.serializer import trace, dump, load
 from .experiment import Experiment
 from .runtime.env_vars import dispatcher_env_vars

nni/common/blob_utils.py

@@ -15,7 +15,6 @@ import tqdm
 
 __all__ = ['NNI_BLOB', 'load_or_download_file', 'upload_file', 'nni_cache_home']
 
-
 # Blob that contains some downloadable files.
 NNI_BLOB = 'https://nni.blob.core.windows.net'
 

nni/common/framework.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+__all__ = ['set_default_framework', 'get_default_framework', 'shortcut_module', 'shortcut_framework']
+
+import importlib
+import os
+import sys
+from typing import Optional, cast
+
+from typing_extensions import Literal
+
+framework_type = Literal['pytorch', 'tensorflow', 'mxnet', 'none']
+"""Supported framework types."""
+
+ENV_NNI_FRAMEWORK = 'NNI_FRAMEWORK'
+
+def framework_from_env() -> framework_type:
+    framework = os.getenv(ENV_NNI_FRAMEWORK, 'pytorch')
+    if framework not in framework_type.__args__:  # type: ignore
+        raise ValueError(f'{framework} does not belong to {framework_type.__args__}')  # type: ignore
+    return cast(framework_type, framework)
+
+
+DEFAULT_FRAMEWORK = framework_from_env()
+
+
+def set_default_framework(framework: framework_type) -> None:
+    """Set default deep learning framework to simplify imports.
+
+    Some functionalities in NNI (e.g., NAS / Compression), relies on an underlying DL framework.
+    For different DL frameworks, the implementation of NNI can be very different.
+    Thus, users need import things tailored for their own framework. For example: ::
+
+        from nni.nas.xxx.pytorch import yyy
+
+    rather than: ::
+
+        from nni.nas.xxx import yyy
+
+    By setting a default framework, shortcuts will be made. As such ``nni.nas.xxx`` will be equivalent to ``nni.nas.xxx.pytorch``.
+
+    Another way to setting it is through environment variable ``NNI_FRAMEWORK``,
+    which needs to be set before the whole process starts.
+
+    If you set the framework with :func:`set_default_framework`,
+    it should be done before all imports (except nni itself) happen,
+    because it will affect other import's behaviors.
+    And the behavior is undefined if the framework is "re"-set in the middle.
+
+    The supported frameworks here are listed below.
+    It doesn't mean that they are fully supported by NAS / Compression in NNI.
+
+    * ``pytorch`` (default)
+    * ``tensorflow``
+    * ``mxnet``
+    * ``none`` (to disable the shortcut-import behavior).
+
+    Examples
+    --------
+    >>> import nni
+    >>> nni.set_default_framework('tensorflow')
+    >>> # then other imports
+    >>> from nni.nas.xxx import yyy
+    """
+
+    # In case 'none' is written as None.
+    if framework is None:
+        framework = 'none'
+
+    global DEFAULT_FRAMEWORK
+    DEFAULT_FRAMEWORK = framework
+
+
+def get_default_framework() -> framework_type:
+    """Retrieve default deep learning framework set either with env variables or manually."""
+    return DEFAULT_FRAMEWORK
+
+
+def shortcut_module(current: str, target: str, package: Optional[str] = None) -> None:
+    """Make ``current`` module an alias of ``target`` module in ``package``."""
+    # Reference: https://github.com/dmlc/dgl/blob/d70a362dba8d46fd9838c79d76998a5e33f22cb7/python/dgl/nn/__init__.py#L27
+    mod = importlib.import_module(target, package)
+    thismod = sys.modules[current]
+    for api, obj in mod.__dict__.items():
+        setattr(thismod, api, obj)
+
+
+def shortcut_framework(current: str) -> None:
+    """Make ``current`` a shortcut of ``current.framework``."""
+    if get_default_framework() != 'none':
+        # Throw ModuleNotFoundError if framework is not supported
+        shortcut_module(current, '.' + get_default_framework(), current)

nni/retiarii/codegen/__init__.py

 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
-from .pytorch import model_to_pytorch_script
+from nni.common.framework import shortcut_framework
+
+shortcut_framework(__name__)
+
+del shortcut_framework

nni/retiarii/codegen/pytorch.py

 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
+__all__ = ['model_to_pytorch_script']
+
 import logging
 import re
 from typing import Dict, List, Tuple, Any, cast

nni/retiarii/evaluator/__init__.py

 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
+from nni.common.framework import shortcut_framework
+
 from .functional import FunctionalEvaluator
+
+shortcut_framework(__name__)
+
+del shortcut_framework

nni/retiarii/execution/base.py

@@ -146,7 +146,7 @@ class BaseExecutionEngine(AbstractExecutionEngine):
     def pack_model_data(cls, model: Model) -> Any:
         mutation_summary = get_mutation_summary(model)
         assert model.evaluator is not None, 'Model evaluator can not be None'
-        return BaseGraphData(codegen.model_to_pytorch_script(model), model.evaluator, mutation_summary)
+        return BaseGraphData(codegen.pytorch.model_to_pytorch_script(model), model.evaluator, mutation_summary)  # type: ignore
 
     @classmethod
     def trial_execute_graph(cls) -> None:

nni/retiarii/experiment/__init__.py

 # Copyright (c) Microsoft Corporation.
-# Licensed under the MIT license.
\ No newline at end of file
+# Licensed under the MIT license.
+
+from nni.common.framework import shortcut_framework
+
+shortcut_framework(__name__)
+
+del shortcut_framework

nni/retiarii/experiment/pytorch.py

@@ -20,7 +20,7 @@ from .config import (
     RetiariiExeConfig, OneshotEngineConfig, BaseEngineConfig,
     PyEngineConfig, CgoEngineConfig, BenchmarkEngineConfig
 )
-from ..codegen import model_to_pytorch_script
+from ..codegen.pytorch import model_to_pytorch_script
 from ..converter import convert_to_graph
 from ..converter.graph_gen import GraphConverterWithShape
 from ..execution import list_models, set_execution_engine
@@ -97,7 +97,7 @@ def debug_mutated_model(base_model, evaluator, applied_mutators):
         a list of mutators that will be applied on the base model for generating a new model
     """
     base_model_ir, applied_mutators = preprocess_model(base_model, evaluator, applied_mutators)
-    from ..strategy import _LocalDebugStrategy
+    from ..strategy.local_debug_strategy import _LocalDebugStrategy
     strategy = _LocalDebugStrategy()
     strategy.run(base_model_ir, applied_mutators)
     _logger.info('local debug completed!')

nni/retiarii/experiment/tensorflow.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.

nni/retiarii/hub/__init__.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+from nni.common.framework import shortcut_framework
+
+shortcut_framework(__name__)
+
+del shortcut_framework

nni/retiarii/nn/__init__.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+from nni.common.framework import shortcut_framework
+
+shortcut_framework(__name__)
+
+del shortcut_framework

nni/retiarii/nn/tensorflow/api.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+from __future__ import annotations
+
+import tensorflow as tf
+
+
+class LayerChoice(tf.keras.Layer):
+    # FIXME: This is only a draft to test multi-framework support, it's not unimplemented at all.
+    pass

nni/retiarii/oneshot/__init__.py

 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
+from nni.common.framework import shortcut_framework
+
 from .interface import BaseOneShotTrainer
+
+shortcut_framework(__name__)
+
+del shortcut_framework

nni/retiarii/strategy/__init__.py

@@ -5,6 +5,5 @@ from .base import BaseStrategy
 from .bruteforce import Random, GridSearch
 from .evolution import RegularizedEvolution
 from .tpe_strategy import TPEStrategy, TPE
-from .local_debug_strategy import _LocalDebugStrategy
 from .rl import PolicyBasedRL
 from .oneshot import DARTS, Proxyless, GumbelDARTS, ENAS, RandomOneShot

nni/retiarii/strategy/local_debug_strategy.py

@@ -24,7 +24,7 @@ class _LocalDebugStrategy(BaseStrategy):
 
     def run_one_model(self, model):
         mutation_summary = get_mutation_summary(model)
-        graph_data = BaseGraphData(codegen.model_to_pytorch_script(model), model.evaluator, mutation_summary)
+        graph_data = BaseGraphData(codegen.pytorch.model_to_pytorch_script(model), model.evaluator, mutation_summary)  # type: ignore
         random_str = ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(6))
         file_name = f'_generated_model/{random_str}.py'
         os.makedirs(os.path.dirname(file_name), exist_ok=True)

test/ut/nas/test_import_nodep.py

+"""To test the cases of importing NAS without certain DL libraries installed."""
+
+import argparse
+import subprocess
+import sys
+
+import pytest
+
+
+def import_related(mask_out):
+    import nni
+    nni.set_default_framework(mask_out)
+    import nni.retiarii
+    import nni.retiarii.evaluator
+    import nni.retiarii.hub
+    import nni.retiarii.strategy  # FIXME: this doesn't work yet
+    import nni.retiarii.experiment
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('masked', choices=['torch', 'torch_none', 'tensorflow'])
+    args = parser.parse_args()
+    if args.masked == 'torch':
+        # https://stackoverflow.com/questions/1350466/preventing-python-code-from-importing-certain-modules
+        sys.modules['torch'] = None
+        import_related('tensorflow')
+    if args.masked == 'torch_none':
+        sys.modules['torch'] = None
+        import_related('none')
+    elif args.masked == 'tensorflow':
+        sys.modules['tensorflow'] = None
+        import_related('pytorch')
+
+
+@pytest.mark.parametrize('framework', ['torch', 'torch_none', 'tensorflow'])
+def test_import_without_framework(framework):
+    subprocess.run([sys.executable, __file__, framework], check=True)
+
+
+if __name__ == '__main__':
+    main()