add trainer.stop and fix a bug for train_by_parallel_executor (#10762)

python/paddle/fluid/tests/book/high-level-api/fit_a_line/test_fit_a_line.py

@@ -57,22 +57,20 @@ def train(use_cuda, train_program, save_dirname):
         optimizer=fluid.optimizer.SGD(learning_rate=0.001))
 
     def event_handler(event):
-        if isinstance(event, fluid.EndEpochEvent):
-            test_metrics = trainer.test(
-                reader=test_reader, feed_order=['x', 'y'])
-            print test_metrics
-            '''
-            
-            ...
-            ['25.768919467926025']
-            ['15.343549569447836']
-            ...
-            
-            '''
-            if float(test_metrics[0]) < 20.0:
+        if isinstance(event, fluid.EndStepEvent):
+            if event.step == 10:
+                test_metrics = trainer.test(
+                    reader=test_reader, feed_order=['x', 'y'])
+                print test_metrics
+                '''
+                ...
+                ['25.768919467926025']
+                ['15.343549569447836']
+                ...
+                '''
                 if save_dirname is not None:
                     trainer.save_params(save_dirname)
-            return
+                trainer.stop()
 
     trainer.train(
         reader=train_reader,

python/paddle/fluid/trainer.py

@@ -100,6 +100,7 @@ class Trainer(object):
                  param_path=None,
                  place=None,
                  parallel=False):
+        self.__stop = False
         self.parallel = parallel
         # 1. we need to generate a framework.Program by calling
         # program_func. Reference: fluid.program_guard in
@@ -210,6 +211,12 @@ class Trainer(object):
                     'TRAINING_ROLE environment variable must be either TRAINER or PSERVER'
                 )
 
+    def stop(self):
+        """
+        stop training
+        """
+        self.__stop = True
+
     def train(self, num_epochs, event_handler, reader=None, feed_order=None):
         """
         Train the model.
@@ -289,6 +296,8 @@ class Trainer(object):
         for epoch_id in range(num_epochs):
             event_handler(BeginEpochEvent(epoch_id))
             for step_id, data in enumerate(reader()):
+                if self.__stop:
+                    return
                 begin_event = BeginStepEvent(epoch_id, step_id)
                 event_handler(begin_event)
                 if begin_event.fetch_metrics:
@@ -327,9 +336,7 @@ class Trainer(object):
             feeder = data_feeder.DataFeeder(
                 feed_list=feed_var_list, place=self.place)
             reader = feeder.decorate_reader(reader, multi_devices=True)
-            for epoch_id in range(num_epochs):
-                self._train_by_any_executor(event_handler, pe, num_epochs,
-                                            reader)
+            self._train_by_any_executor(event_handler, pe, num_epochs, reader)
 
     def _get_parallel_executor(self):
         return getattr(self, 'parallel_executor', None)