Temporally disable zero_copy (#27248)

* temporally disable zero_copy

* add test

* follow comments

python/paddle/fluid/dygraph/base.py

@@ -25,6 +25,7 @@ from .tracer import Tracer
 import logging
 import objgraph
 from ..data_feeder import convert_dtype
+import warnings
 
 __all__ = [
     'no_grad', 'no_grad_', 'grad', 'guard', 'enable_dygraph', 'disable_dygraph',
@@ -612,7 +613,7 @@ def to_variable(value, name=None, zero_copy=None, dtype=None):
             refer to :ref:`api_guide_Name` . 
         zero_copy(bool, optional): Whether to share memory with the input numpy 
             array. This parameter only works with CPUPlace and will be set to 
-            True when it is None. Default: None.
+            True when it is None. Default: None. (Note: zero_copy is discarded temporally for some reason.)
         dtype(str, optional): The desired data type of returned ``Variable`` .
             Can be 'bool' , 'float16' , 'float32' , 'float64' , 'int8' , 'int16' , 
             'int32' , 'int64' , 'uint8' . Default: None.
@@ -665,8 +666,17 @@ def to_variable(value, name=None, zero_copy=None, dtype=None):
     else:
         if isinstance(framework._current_expected_place(),
                       framework.core.CPUPlace):
-            if zero_copy is None:
-                zero_copy = True
+            #TODO(zhiqiu): we found two problems when enable zero_copy on CPUPlace.
+            # (1): eigen requires 16-bytes alignments, but the data of numpy array may not statisfy. 
+            # Details: https://eigen.tuxfamily.org/dox/group__TopicUnalignedArrayAssert.html
+            # (2): when used in flask framework, it may result in hang.
+            # Details: https://github.com/PaddlePaddle/Paddle/issues/26635
+            # So, we temporally diable the zero_copy strategy.
+            if zero_copy == True:
+                warnings.warn(
+                    "Currently, zero_copy is not supported, and it will be discarded."
+                )
+                zero_copy = False
         else:
             assert not zero_copy, "zero_copy mode can only be used with CPUPlace"
 

python/paddle/fluid/tests/unittests/test_imperative_numpy_bridge.py

@@ -15,18 +15,26 @@
 import unittest
 import numpy as np
 import paddle.fluid as fluid
+import warnings
 
 
 class TestImperativeNumpyBridge(unittest.TestCase):
     def test_tensor_from_numpy(self):
         data_np = np.array([[2, 3, 1]]).astype('float32')
         with fluid.dygraph.guard(fluid.CPUPlace()):
-            var = fluid.dygraph.to_variable(data_np, zero_copy=True)
-            self.assertTrue(np.array_equal(var.numpy(), data_np))
-            data_np[0][0] = 4
-            self.assertEqual(data_np[0][0], 4)
-            self.assertEqual(var[0][0].numpy()[0], 4)
-            self.assertTrue(np.array_equal(var.numpy(), data_np))
+            with warnings.catch_warnings(record=True) as w:
+                warnings.simplefilter("always")
+                var = fluid.dygraph.to_variable(data_np, zero_copy=True)
+                assert "Currently, zero_copy is not supported, and it will be discarded." in str(
+                    w[-1].message)
+            # Temporally diable zero_copy
+            # var = fluid.dygraph.to_variable(data_np, zero_copy=True)
+            # self.assertTrue(np.array_equal(var.numpy(), data_np))
+            # data_np[0][0] = 4
+            # self.assertEqual(data_np[0][0], 4)
+            # self.assertEqual(var[0][0].numpy()[0], 4)
+            # self.assertTrue(np.array_equal(var.numpy(), data_np))
+
             var2 = fluid.dygraph.to_variable(data_np, zero_copy=False)
             self.assertTrue(np.array_equal(var2.numpy(), data_np))
             data_np[0][0] = -1

python/paddle/tensor/creation.py

@@ -63,8 +63,7 @@ def to_tensor(data, dtype=None, place=None, stop_gradient=True):
 
     If the ``data`` is already a tensor, and ``dtype`` or ``place`` does't change, no copy 
     will be performed and return origin tensor, otherwise a new tensor will be constructed
-    and returned. Similarly, if the data is an numpy\.ndarray of with the same ``dtype`` 
-    and the current place is cpu, no copy will be performed.
+    and returned. 
 
     The ``ComplexTensor`` is a unique type of paddle. If x is ``ComplexTensor``, then 
     ``x.real`` is the real part, and ``x.imag`` is the imaginary part.
@@ -209,20 +208,20 @@ def to_tensor(data, dtype=None, place=None, stop_gradient=True):
             value=data,
             place=place,
             persistable=False,
-            zero_copy=True,
+            zero_copy=False,
             stop_gradient=stop_gradient)
     else:
         name = unique_name.generate('generated_tensor')
         real_tensor = paddle.Tensor(
             value=data.real,
             place=place,
-            zero_copy=True,
+            zero_copy=False,
             name=name + ".real",
             stop_gradient=stop_gradient)
         imag_tensor = paddle.Tensor(
             value=data.imag,
             place=place,
-            zero_copy=True,
+            zero_copy=False,
             name=name + ".imag",
             stop_gradient=stop_gradient)
         return paddle.ComplexTensor(real_tensor, imag_tensor)