Merge pull request #9558 from typhoonzero/fix_dist_transpile_one_trainer

fix single pserver single trainer error

python/paddle/fluid/distribute_transpiler.py

@@ -276,20 +276,25 @@ class DistributeTranspiler:
             suff_idx = v.name.find(".trainer_")
             if suff_idx >= 0:
                 orig_var_name = v.name[:suff_idx]
-            pserver_program.global_block().create_var(
+            else:
+                orig_var_name = v.name
+            single_trainer_var = pserver_program.global_block().create_var(
                 name=orig_var_name,
                 persistable=True,
                 type=v.type,
                 dtype=v.dtype,
                 shape=v.shape)
-            for trainer_id in xrange(self.trainers):
-                var = pserver_program.global_block().create_var(
-                    name="%s.trainer_%d" % (orig_var_name, trainer_id),
-                    persistable=False,
-                    type=v.type,
-                    dtype=v.dtype,
-                    shape=v.shape)
-                recv_inputs.append(var)
+            if self.trainers > 1:
+                for trainer_id in xrange(self.trainers):
+                    var = pserver_program.global_block().create_var(
+                        name="%s.trainer_%d" % (orig_var_name, trainer_id),
+                        persistable=False,
+                        type=v.type,
+                        dtype=v.dtype,
+                        shape=v.shape)
+                    recv_inputs.append(var)
+            else:
+                recv_inputs.append(single_trainer_var)
 
         # step3
         optimize_block = pserver_program.create_block(0)
@@ -511,8 +516,11 @@ class DistributeTranspiler:
 
     def _append_split_op(self, program, gradblocks):
         # Split variables that need to be split and append respective ops
+        add_suffix = False
+        if self.trainers > 1:
+            add_suffix = True
         var_mapping = self._create_vars_from_blocklist(
-            program, gradblocks, add_trainer_suffix=True)
+            program, gradblocks, add_trainer_suffix=add_suffix)
         for varname, splited_vars in var_mapping.iteritems():
             # variable that don't need to split have empty splited_vars
             if len(splited_vars) <= 1: