Add is_test for while_op (#12874)

* add is_test for while_op

* Change API

paddle/fluid/API.spec

@@ -191,7 +191,7 @@ paddle.fluid.layers.argsort ArgSpec(args=['input', 'axis', 'name'], varargs=None
 paddle.fluid.layers.ones ArgSpec(args=['shape', 'dtype', 'force_cpu'], varargs=None, keywords=None, defaults=(False,))
 paddle.fluid.layers.zeros ArgSpec(args=['shape', 'dtype', 'force_cpu'], varargs=None, keywords=None, defaults=(False,))
 paddle.fluid.layers.reverse ArgSpec(args=['x', 'axis'], varargs=None, keywords=None, defaults=None)
-paddle.fluid.layers.While.__init__ ArgSpec(args=['self', 'cond', 'name'], varargs=None, keywords=None, defaults=(None,))
+paddle.fluid.layers.While.__init__ ArgSpec(args=['self', 'cond', 'is_test', 'name'], varargs=None, keywords=None, defaults=(False, None))
 paddle.fluid.layers.While.block ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None)
 paddle.fluid.layers.Switch.__init__ ArgSpec(args=['self', 'name'], varargs=None, keywords=None, defaults=(None,))
 paddle.fluid.layers.Switch.case ArgSpec(args=['self', 'condition'], varargs=None, keywords=None, defaults=None)

paddle/fluid/operators/while_op.cc

@@ -58,11 +58,15 @@ class WhileOp : public framework::OperatorBase {
     PADDLE_ENFORCE(platform::is_cpu_place(cond.place()),
                    "Condition of while op must in CPU memory.");
 
+    bool is_test = Attr<bool>("is_test");
     auto ctx = executor.Prepare(*program, block->ID());
     while (cond.data<bool>()[0]) {
       auto &current_scope = scope.NewScope();
       step_scopes->push_back(&current_scope);
       executor.RunPreparedContext(ctx.get(), &current_scope, false);
+      if (is_test) {
+        scope.DeleteScope(&current_scope);
+      }
     }
   }
 };
@@ -88,6 +92,7 @@ class WhileOpMaker : public framework::OpProtoAndCheckerMaker {
               "variables generated in the i'th step.");
     AddAttr<framework::BlockDesc *>(kStepBlock,
                                     "The step block inside WhileOp");
+    AddAttr<bool>("is_test", "True if in test phase.").SetDefault(false);
     AddComment(R"DOC(
 )DOC");
   }
@@ -103,6 +108,8 @@ class WhileGradOp : public framework::OperatorBase {
  private:
   void RunImpl(const framework::Scope &scope,
                const platform::Place &dev_place) const override {
+    PADDLE_ENFORCE(!Attr<bool>("is_test"),
+                   "GradOp is only callable when is_test is false");
     // get device context from pool
     platform::DeviceContextPool &pool = platform::DeviceContextPool::Instance();
     auto &dev_ctx = *pool.Get(dev_place);

python/paddle/fluid/layers/control_flow.py

@@ -661,6 +661,7 @@ class While(object):
 
     Args:
         cond (Variable): condition used to compare.
+        is_test(bool): A flag indicating whether execution is in test phase.
         name (str): The name of this layer.
 
     Examples:
@@ -683,7 +684,7 @@ class While(object):
     IN_WHILE_BLOCK = 1
     AFTER_WHILE_BLOCK = 2
 
-    def __init__(self, cond, name=None):
+    def __init__(self, cond, is_test=False, name=None):
         self.helper = LayerHelper("while", name=name)
         self.status = While.BEFORE_WHILE_BLOCK
         if not isinstance(cond, Variable):
@@ -694,6 +695,7 @@ class While(object):
         if reduce(lambda a, b: a * b, cond.shape, 1) != 1:
             raise TypeError("condition should be a bool scalar")
         self.cond_var = cond
+        self.is_test = is_test
 
     def block(self):
         return WhileGuard(self)
@@ -735,7 +737,8 @@ class While(object):
             },
             outputs={'Out': out_vars,
                      'StepScopes': [step_scope]},
-            attrs={'sub_block': while_block})
+            attrs={'sub_block': while_block,
+                   "is_test": self.is_test})
 
 
 def lod_rank_table(x, level=0):