diff --git a/demo/mnist/api_train.py b/demo/mnist/api_train.py
index 425c5f897a9c254bdae2aa1a6e91a4ce7a69874e..52cc13c5a3eaeece68d4198ee7ebd41d572f8b11 100644
--- a/demo/mnist/api_train.py
+++ b/demo/mnist/api_train.py
@@ -62,14 +62,14 @@ def main():
         train_data_generator = input_order_converter(
             read_from_mnist(train_file))
         for batch_id, data_batch in enumerate(
-                generator_to_batch(train_data_generator, 256)):
+                generator_to_batch(train_data_generator, 2048)):
             trainRole = updater.startBatch(len(data_batch))
 
-            def update_callback(param):
+            def updater_callback(param):
                 updater.update(param)
 
             m.forwardBackward(
-                converter(data_batch), outArgs, trainRole, update_callback)
+                converter(data_batch), outArgs, trainRole, updater_callback)
 
             cost_vec = outArgs.getSlotValue(0)
             cost_vec = cost_vec.copyToNumpyMat()
diff --git a/paddle/api/CMakeLists.txt b/paddle/api/CMakeLists.txt
index 39fe43556595ccfccb6190314ff43d323dc5c2e9..a7f17e186bf6b452628a24ab514c8e9aa2658e9d 100644
--- a/paddle/api/CMakeLists.txt
+++ b/paddle/api/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(API_SOURCES
     Arguments.cpp
     ConfigParser.cpp
+    Evaluator.cpp
     GradientMachine.cpp
     Matrix.cpp
     Parameter.cpp
@@ -63,6 +64,15 @@ install(DIRECTORY ${PROJ_ROOT}/paddle/dist/
 
 add_custom_target(python_api_wheel ALL DEPENDS
   ${PROJ_ROOT}/paddle/dist/.timestamp)
+add_dependencies(python_api_wheel python_swig_sources
+  paddle_parameter
+  paddle_math
+  paddle_utils
+  paddle_gserver
+  paddle_pserver
+  paddle_trainer
+  paddle_api
+  paddle_cuda)
 
 if(WITH_TESTING)
     add_subdirectory(test)
diff --git a/paddle/api/Evaluator.cpp b/paddle/api/Evaluator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..c30e09876397e37ef9ed4ec3200d1aa372ceb609
--- /dev/null
+++ b/paddle/api/Evaluator.cpp
@@ -0,0 +1,29 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+#include <sstream>
+#include "PaddleAPI.h"
+#include "PaddleAPIPrivate.h"
+
+Evaluator::Evaluator() : m(new EvaluatorPrivate()) {}
+Evaluator::~Evaluator() { delete m; }
+
+void Evaluator::start() { m->rawPtr->start(); }
+
+void Evaluator::finish() { m->rawPtr->finish(); }
+
+std::string Evaluator::toString() {
+  std::ostringstream sout;
+  m->rawPtr->printStats(sout);
+  return sout.str();
+}
diff --git a/paddle/api/GradientMachine.cpp b/paddle/api/GradientMachine.cpp
index 2cece2109795a986966d2decfdde27b2759e51cc..0d1e17529611d11136914cb810b0633e0afccedf 100644
--- a/paddle/api/GradientMachine.cpp
+++ b/paddle/api/GradientMachine.cpp
@@ -162,3 +162,13 @@ SequenceGenerator* GradientMachine::asSequenceGenerator(
   r->setBeamSize(beam_size);
   return r;
 }
+
+Evaluator* GradientMachine::makeEvaluator() {
+  auto ev = new Evaluator();
+  ev->m->rawPtr = m->machine->makeEvaluator();
+  return ev;
+}
+
+void GradientMachine::eval(Evaluator* evaluator) {
+  m->machine->eval(evaluator->m->rawPtr);
+}
diff --git a/paddle/api/Paddle.swig b/paddle/api/Paddle.swig
index b0fa8beb166b3438d2b6cbf7afd46791979f41bb..7a110a90b84fcbbabd32639a97977322c2aecc2a 100644
--- a/paddle/api/Paddle.swig
+++ b/paddle/api/Paddle.swig
@@ -97,6 +97,7 @@ namespace std {
 %rename(__setitem__) Vector::set;
 %rename(__len__) Vector::getSize;
 %rename(__call__) ParameterTraverseCallback::apply;
+%rename(__repr__) Evaluator::toString;
 
 %apply (float* INPLACE_ARRAY2, int DIM1, int DIM2) { 
   (float* data, int dim1, int dim2) 
@@ -167,6 +168,7 @@ namespace std {
 %newobject GradientMachine::asSequenceGenerator;
 %newobject GradientMachine::getParameter;
 %newobject GradientMachine::getLayerOutput;
+%newobject GradientMachine::makeEvaluator;
 %newobject TrainerConfig::createFromTrainerConfigFile;
 %newobject TrainerConfig::getModelConfig;
 %newobject TrainerConfig::getOptimizationConfig;
diff --git a/paddle/api/PaddleAPI.h b/paddle/api/PaddleAPI.h
index cc49e6a09d5dee41ff47606025fcc492559aa958..413c38514646211befc18a83a2d7ce70644b5183 100644
--- a/paddle/api/PaddleAPI.h
+++ b/paddle/api/PaddleAPI.h
@@ -685,7 +685,7 @@ private:
 };
 
 class SequenceGenerator;
-
+class Evaluator;
 struct GradientMachinePrivate;
 class GradientMachine {
 private:
@@ -770,6 +770,10 @@ public:
       size_t max_length = 100UL,
       size_t beam_size = -1UL);
 
+  Evaluator* makeEvaluator();
+
+  void eval(Evaluator* evaluator);
+
 private:
   GradientMachinePrivate* m;
 
@@ -809,6 +813,27 @@ private:
   ParameterUpdaterPrivate* m;
 };
 
+struct EvaluatorPrivate;
+class Evaluator {
+private:
+  Evaluator();
+  DISABLE_COPY_AND_ASSIGN(Evaluator);
+
+public:
+  ~Evaluator();
+
+  void start();
+
+  void finish();
+
+  std::string toString();
+
+private:
+  EvaluatorPrivate* m;
+
+  friend class GradientMachine;
+};
+
 struct TrainerPrivate;
 class Trainer {
 private:
diff --git a/paddle/api/PaddleAPIPrivate.h b/paddle/api/PaddleAPIPrivate.h
index 905668a62f24fbd8db4a8833d92df2fe43b6d0c1..f41352bfec7c3333bde9509957aba8c5f373b9f2 100644
--- a/paddle/api/PaddleAPIPrivate.h
+++ b/paddle/api/PaddleAPIPrivate.h
@@ -14,10 +14,10 @@ limitations under the License. */
 #pragma once
 #include <memory>
 #include "PaddleAPI.h"
+#include "paddle/gserver/evaluators/Evaluator.h"
 #include "paddle/gserver/gradientmachines/GradientMachine.h"
-#include "paddle/trainer/TrainerConfigHelper.h"
-
 #include "paddle/parameter/ParameterUpdaterBase.h"
+#include "paddle/trainer/TrainerConfigHelper.h"
 
 struct GradientMachinePrivate {
   std::shared_ptr<paddle::GradientMachine> machine;
@@ -88,3 +88,10 @@ struct ParameterPrivate {
     }
   }
 };
+
+struct EvaluatorPrivate {
+  paddle::Evaluator* rawPtr;
+
+  EvaluatorPrivate() : rawPtr(nullptr) {}
+  ~EvaluatorPrivate() { delete rawPtr; }
+};
diff --git a/paddle/api/ParameterUpdater.cpp b/paddle/api/ParameterUpdater.cpp
index fba47620249dbc7543678b3e7e969a21ff32647a..91c839276280804bc9decc87c245728e0893de51 100644
--- a/paddle/api/ParameterUpdater.cpp
+++ b/paddle/api/ParameterUpdater.cpp
@@ -29,7 +29,7 @@ ParameterUpdater *ParameterUpdater::createLocalUpdater(
 ParameterUpdater::~ParameterUpdater() { delete m; }
 
 void ParameterUpdater::init(const GradientMachine &gm) {
-  m->updater->init(gm.m->machine->getParameters());
+  m->updater->init(gm.m->machine->getNonStaticParameters());
 }
 
 void ParameterUpdater::startPass() { m->updater->startPass(); }