Enable fastseq generate CLI to handle the empty shard correctly (#82)

* Handle the empty shard

* Remove unused variable

fastseq/optimizer/fairseq/generate.py

@@ -60,7 +60,7 @@ class IOProcess(Process):
 
         self.args = args
         self.message_queue = message_queue
-        self.has_target = True
+        self.has_target = False
 
     def run(self):
         while True:
@@ -71,6 +71,7 @@ class IOProcess(Process):
                     self.scorer.add_string(t, h)
                 else:
                     self.scorer.add(t, h)
+                self.has_target = True
             elif msg == GENERATE_FINISHED:
                 if self.has_target:
                     print('| Generate {} with beam={}: {}'.format(
@@ -124,7 +125,6 @@ class PostProcess(Process):
         self.task = task
         self.data_queue = data_queue
         self.message_queue = message_queue
-        self.has_target = True
         if args.decode_hypothesis:
             self.tokenizer = encoders.build_tokenizer(args)
             self.bpe = encoders.build_bpe(args)
@@ -402,10 +402,13 @@ def main_v1(args):
     for p in p_list:
         p.join()
 
+    sent_throught = num_sentences / gen_timer.sum if num_sentences > 0 else 0
+    tokens_throught = 1. / gen_timer.avg if num_sentences > 0 else 0
+
     message_queue.put(
         '| Translated {} sentences ({} tokens) in {:.1f}s ({:.2f} sentences/s, {:.2f} tokens/s)'. # pylint: disable=line-too-long
-        format(num_sentences, gen_timer.n, gen_timer.sum,
-               num_sentences / gen_timer.sum, 1. / gen_timer.avg))
+        format(num_sentences, gen_timer.n, gen_timer.sum, sent_throught,
+               tokens_throught))
 
     message_queue.put(GENERATE_FINISHED)
     io_process.join()