chore: import upstream snapshot with attribution

python/paddle/nn/initializer/lazy_init.py

@@ -0,0 +1,144 @@
+# Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from ...base import framework
+
+if TYPE_CHECKING:
+    from types import TracebackType
+
+
+__all__ = ["LazyGuard"]
+
+
+class LazyInitHelper:
+    """
+    A Helper Context to trigger switching mode between dygraph and static graph mode,
+    and holds the startup program resource.
+    """
+
+    def __init__(self):
+        self._state = False
+        self._tracer = None
+        self._in_guard = False
+
+    def enable(self):
+        """
+        Switch into lazy mode.
+
+        NOTE(dev): This is a very low level API and not exposed for user.
+        """
+        if self._state:
+            return
+        assert framework.in_dygraph_mode(), (
+            "LazyInit.enable() is only available in dygraph mode."
+        )
+        self._state = True
+
+    def disable(self):
+        """
+        Exit from lazy mode.
+
+        NOTE(dev): This is a very low level API and not exposed for user.
+        """
+        if not self._state:
+            return
+        self._state = False
+
+    def __enter__(self):
+        """
+        Switch into lazy mode and set _dygraph_tracer_ with None to convert
+        dygraph mode into static graph mode.
+        """
+        self.enable()
+        if self._in_guard:
+            return
+        self._tracer = framework.global_var._dygraph_tracer_
+        framework.global_var._dygraph_tracer_ = None
+        self._in_guard = True
+
+    def __exit__(self, *args, **kwargs):
+        """
+        Exit from lazy mode and recover _dygraph_tracer_.
+        """
+        self.disable()
+        if not self._in_guard:
+            return
+        assert self._tracer is not None
+        framework.global_var._dygraph_tracer_ = self._tracer
+        self._tracer = None
+        self._in_guard = False
+
+    @property
+    def state(self):
+        return self._state
+
+
+_lazy_init_helper = LazyInitHelper()
+
+
+def lazy_init_helper():
+    global _lazy_init_helper
+    return _lazy_init_helper
+
+
+class LazyGuard:
+    """
+    LazyGuard is a wrapper interface for nn.Layer, it forwards the construct
+    process of user defined Layer. Meanwhile, it provides necessary API to
+    trigger EagerParamBase Lazy Initialization and get startup Program.
+
+    Examples:
+
+        .. code-block:: pycon
+
+            >>> from paddle import LazyGuard
+            >>> from paddle.nn import Linear
+
+            >>> with LazyGuard():
+            ...     # w and b are initialized lazily and have no memory.
+            ...     net = Linear(10, 10)
+            >>> for param in net.parameters():
+            ...     # Initialize param and allocate memory explicitly.
+            ...     param.initialize()
+    """
+
+    def __enter__(self) -> None:
+        """
+        Construct instance from class_obj by Lazy Initializing parameters.
+
+        Examples:
+
+            .. code-block:: pycon
+
+                >>> from paddle import LazyGuard
+                >>> from paddle.nn import Linear
+
+                >>> with LazyGuard():
+                ...     fc = LazyInit(Linear)(10, 10)
+                >>> for param in fc.parameters():
+                ...     param.initialize()
+        """
+        lazy_init_helper().enable()
+
+    def __exit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> None:
+        lazy_init_helper().disable()