From 61d7027776f7bd4a16cbb4931fd70599cab22186 Mon Sep 17 00:00:00 2001
From: Chen Weihang <chenweihang@baidu.com>
Date: Wed, 16 Dec 2020 20:15:02 -0600
Subject: [PATCH] [Cherry-pick][bug fix] fix train eval set error in static
 mode (#29540) (#29571)

Fix Layer train eval setting failed in static mode, more details please see #29540
---
 python/paddle/fluid/dygraph/layers.py           | 14 ++++++++++----
 .../paddle/fluid/tests/unittests/test_layers.py | 17 +++++++++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/python/paddle/fluid/dygraph/layers.py b/python/paddle/fluid/dygraph/layers.py
index fe60c24ff36..fd824de3a1e 100644
--- a/python/paddle/fluid/dygraph/layers.py
+++ b/python/paddle/fluid/dygraph/layers.py
@@ -132,8 +132,11 @@ class Layer(core.Layer):
                 out = mylayer(x)
 
         """
-        # global setting
-        framework._dygraph_tracer().train_mode()
+        # global setting in dygraph
+        # NOTE(chenweihang): nn.Layer also can be used in static mode,
+        # but _dygraph_tracer() can not be called in static mode
+        if in_dygraph_mode():
+            framework._dygraph_tracer().train_mode()
         # Layer-level setting
         self.training = True
         for layer in self.sublayers():
@@ -170,8 +173,11 @@ class Layer(core.Layer):
                 print(out)
 
         """
-        # global setting
-        framework._dygraph_tracer().eval_mode()
+        # global setting in dygraph
+        # NOTE(chenweihang): nn.Layer also can be used in static mode,
+        # but _dygraph_tracer() can not be called in static mode
+        if in_dygraph_mode():
+            framework._dygraph_tracer().eval_mode()
         # Layer-level setting
         self.training = False
         for layer in self.sublayers():
diff --git a/python/paddle/fluid/tests/unittests/test_layers.py b/python/paddle/fluid/tests/unittests/test_layers.py
index 8ae5264381e..35ecbd6bf10 100644
--- a/python/paddle/fluid/tests/unittests/test_layers.py
+++ b/python/paddle/fluid/tests/unittests/test_layers.py
@@ -3701,6 +3701,23 @@ class TestLayerParameterTrainableSet(unittest.TestCase):
             self.assertFalse(net.weight.trainable)
 
 
+class TestLayerTrainingAttribute(unittest.TestCase):
+    def test_set_train_eval_in_dynamic_mode(self):
+        with fluid.dygraph.guard():
+            net = paddle.nn.Dropout()
+            net.train()
+            self.assertTrue(net.training)
+            net.eval()
+            self.assertFalse(net.training)
+
+    def test_set_train_eval_in_static_mode(self):
+        net = paddle.nn.Dropout()
+        net.train()
+        self.assertTrue(net.training)
+        net.eval()
+        self.assertFalse(net.training)
+
+
 if __name__ == '__main__':
     paddle.enable_static()
     unittest.main()
-- 
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