Speedup reader check_input_array when item is array (#25395) (#25848)

Author: wangxicoding

python/paddle/fluid/reader.py

@@ -96,6 +96,18 @@ def __iter__(self):
     def __next__(self):
         raise NotImplementedError()
 
+    @classmethod
+    def _check_input_array(cls, item):
+        arr = np.asarray(item)
+        if arr.dtype == np.object:
+            raise TypeError(
+                "\n\tFaild to convert input data to a regular ndarray :\n\t* Usually "
+                "this means the input data contains nested lists with different lengths. "
+                "\n\t* Check the reader function passed to 'decorate_batch_generator'"
+                " to locate the data causes this issue.\n\t* Please consider using "
+                "'fluid.create_lod_tensor' to convert it to a LoD-Tensor.")
+        return arr
+
 
 class DataLoader(object):
     """
@@ -806,17 +818,6 @@ def __next__(self):
             self._reset()
             six.reraise(*sys.exc_info())
 
-    @classmethod
-    def _check_input_array(cls, item):
-        arr = np.array(item)
-        if arr.dtype == np.object:
-            raise TypeError(
-                "\n\tFaild to convert input data to a regular ndarray :\n\t* Usually "
-                "this means the input data contains nested lists with different lengths. "
-                "\n\t* Check the reader function passed to 'decorate_batch_generator'"
-                " to locate the data causes this issue.\n\t* Please consider using "
-                "'fluid.create_lod_tensor' to convert it to a LoD-Tensor.")
-
     def _exit_thread_expectedly(self):
         self._thread_done_event.set()
         self._blocking_queue.close()
@@ -893,7 +894,7 @@ def _reader_thread_loop_for_singleprocess(self):
                 array = core.LoDTensorArray()
                 for item in sample:
                     if not isinstance(item, core.LoDTensor):
-                        self._check_input_array(item)
+                        item = self._check_input_array(item)
                         tmp = core.LoDTensor()
                         tmp.set(item, core.CPUPlace())
                         item = tmp
@@ -1114,19 +1115,6 @@ def reset(self):
         assert not self._iterable, "reset() cannot be called when DataLoader is iterable"
         self._reset()
 
-    @classmethod
-    def _check_input_array(cls, item):
-        arr = np.array(item)
-        if arr.dtype == np.object:
-            raise TypeError((
-                "\n\tFaild to convert input data to a regular ndarray :\n\t* Usually "
-                "this means the input data contains nested lists with different lengths. "
-                "\n\t* Check the reader function passed to 'decorate_batch_generator'"
-                " to locate the data causes this issue.\n\t* Please consider using "
-                "'fluid.create_lod_tensor' to convert it to a LoD-Tensor."))
-
-        return arr
-
     def _start(self):
         def __thread_main__():
             try: