fix dist sparse l2 decay

test=develop

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

@@ -235,7 +235,6 @@ class DistSeResneXt2x2(TestDistRunnerBase):
 
         bd = [step * e for e in epochs]
         base_lr = 0.1
-        lr = []
         lr = [base_lr * (0.1**i) for i in range(len(bd) + 1)]
 
         optimizer = fluid.optimizer.Momentum(

python/paddle/fluid/transpiler/distribute_transpiler.py

@@ -744,12 +744,6 @@ class DistributeTranspiler(object):
             elif op not in lr_ops:
                 self._append_pserver_non_opt_ops(block, op)
 
-        def __op_have_grad_input__(op):
-            for varname in op.input_arg_names:
-                if varname.find("@GRAD") >= 0:
-                    return varname
-            return ""
-
         def __clone_lr_op_sub_block__(op, program, lr_block):
             if not op.has_attr('sub_block'):
                 return
@@ -800,7 +794,7 @@ class DistributeTranspiler(object):
             merged_var = None
             for _, op in enumerate(self.optimize_ops):
                 # find the origin grad var before clipping/L2Decay,
-                # merged_var should be the input var name of L2Decaybuil
+                # merged_var should be the input var name of L2Decay
                 grad_varname_for_block = op.attr(OP_ROLE_VAR_ATTR_NAME)[1]
                 if op.attr(OP_ROLE_VAR_ATTR_NAME)[
                         0] == optimize_target_param_name:
@@ -1278,9 +1272,8 @@ class DistributeTranspiler(object):
         # create table param and grad var in pserver program
         # create table optimize block in pserver program
         table_opt_op = [
-            op for op in self.optimize_ops
-            if 'Param' in op.input_names and op.input("Param")[0] ==
-            self.table_name
+            op for op in self.optimize_ops if 'Param' in op.input_names and
+            op.input("Param")[0] == self.table_name
         ][0]
 
         origin_param_var = self.origin_program.global_block().vars[
@@ -1675,6 +1668,15 @@ class DistributeTranspiler(object):
             if key == "Grad":
                 if self.config.enable_dc_asgd:
                     new_inputs[key] = dc
+                else:
+                    # Note!! This is for l2decay on sparse gradient, because it will create a new tensor for
+                    # decayed gradient but not inplace modify the origin one
+                    origin_grad_name = opt_op.input(key)[0]
+                    if core.kNewGradSuffix(
+                    ) in origin_grad_name and pserver_block.has_var(
+                            origin_grad_name):
+                        new_grad = pserver_block.var(origin_grad_name)
+                        new_inputs[key] = new_grad
                     else:
                         new_inputs[key] = merged_var
             elif key == "Param":