fix drop_last not work on IterableDataset (#34801)

* fix drop_last not work in IterableDataset. test=develop

python/paddle/fluid/dataloader/dataloader_iter.py

@@ -59,6 +59,7 @@ class _DataLoaderIterBase(object):
         self._places = loader.places
         self._return_list = loader.return_list
         self._batch_sampler = loader.batch_sampler
+        self._drop_last = loader.drop_last
         self._auto_collate_batch = loader.auto_collate_batch
         self._num_workers = loader.num_workers
         self._use_buffer_reader = loader.use_buffer_reader
@@ -111,7 +112,7 @@ class _DataLoaderIterSingleProcess(_DataLoaderIterBase):
 
         self._dataset_fetcher = _DatasetKind.create_fetcher(
             self._dataset_kind, self._dataset, self._auto_collate_batch,
-            self._collate_fn, True)
+            self._collate_fn, self._drop_last)
 
         # NOTE: _structrue_infos used to record the data structure of
         # batch to restore batch structure after reading Tensor
@@ -309,8 +310,8 @@ class _DataLoaderIterMultiProcess(_DataLoaderIterBase):
                 args=(self._dataset, self._dataset_kind, indices_queue,
                       self._data_queue, self._workers_done_event,
                       self._auto_collate_batch, self._collate_fn,
-                      self._worker_init_fn, i, self._num_workers,
-                      self._use_shared_memory))
+                      self._drop_last, self._worker_init_fn, i,
+                      self._num_workers, self._use_shared_memory))
             worker.daemon = True
             worker.start()
             self._workers.append(worker)

python/paddle/fluid/dataloader/worker.py

@@ -253,7 +253,7 @@ def _generate_states(base_seed=0, worker_id=0):
 
 
 def _worker_loop(dataset, dataset_kind, indices_queue, out_queue, done_event,
-                 auto_collate_batch, collate_fn, init_fn, worker_id,
+                 auto_collate_batch, collate_fn, drop_last, init_fn, worker_id,
                  num_workers, use_shared_memory):
     try:
         # NOTE: [ mmap files clear ] When the child process exits unexpectedly,
@@ -282,8 +282,9 @@ def _worker_loop(dataset, dataset_kind, indices_queue, out_queue, done_event,
         try:
             if init_fn is not None:
                 init_fn(worker_id)
-            fetcher = _DatasetKind.create_fetcher(
-                dataset_kind, dataset, auto_collate_batch, collate_fn, True)
+            fetcher = _DatasetKind.create_fetcher(dataset_kind, dataset,
+                                                  auto_collate_batch,
+                                                  collate_fn, drop_last)
         except:
             init_exception = _WorkerException(worker_id)
 

python/paddle/fluid/reader.py

@@ -401,6 +401,7 @@ class DataLoader(object):
                     shuffle=shuffle,
                     drop_last=drop_last)
 
+        self.drop_last = drop_last
         self.auto_collate_batch = self.batch_sampler is not None
 
         self.pin_memory = False

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

@@ -397,5 +397,30 @@ class TestDataLoaderGenerateStates(unittest.TestCase):
             assert out == outp
 
 
+class TestDatasetWithDropLast(unittest.TestCase):
+    def run_main(self, dataset, num_samples, batch_size):
+        for num_workers in [0, 1]:
+            for drop_last in [True, False]:
+                steps = (num_samples + (1 - int(drop_last)) * \
+                        (batch_size - 1)) // batch_size
+                dataloader = DataLoader(
+                    dataset,
+                    batch_size=batch_size,
+                    drop_last=drop_last,
+                    num_workers=num_workers)
+                datas = []
+                for data in dataloader:
+                    datas.append(data)
+                assert len(datas) == steps
+
+    def test_map_dataset(self):
+        dataset = RandomDataset(10)
+        self.run_main(dataset, 10, 3)
+
+    def test_iterable_dataset(self):
+        dataset = RandomIterableDataset(10)
+        self.run_main(dataset, 10, 3)
+
+
 if __name__ == '__main__':
     unittest.main()

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

@@ -180,7 +180,7 @@ class TestDataLoaderWorkerLoop(unittest.TestCase):
                 indices_queue.put(None)
                 _worker_loop(loader._dataset, 0, indices_queue,
                              loader._data_queue, loader._workers_done_event,
-                             True, _collate_fn, _init_fn, 0, 1,
+                             True, _collate_fn, True, _init_fn, 0, 1,
                              loader._use_shared_memory)
                 self.assertTrue(False)
         except AssertionError:
@@ -224,7 +224,7 @@ class TestDataLoaderWorkerLoop(unittest.TestCase):
                 loader._workers_done_event.set()
                 _worker_loop(loader._dataset, 0, indices_queue,
                              loader._data_queue, loader._workers_done_event,
-                             True, _collate_fn, _init_fn, 0, 1,
+                             True, _collate_fn, True, _init_fn, 0, 1,
                              loader._use_shared_memory)
                 self.assertTrue(True)
         except AssertionError: