diff --git a/paddle/fluid/lite/CMakeLists.txt b/paddle/fluid/lite/CMakeLists.txt
index 15f2f30ba4bd2cf24b5a2007f0ef8ee784e856e7..0af924424ac1c37953e2667e3322f0e27859fd7c 100644
--- a/paddle/fluid/lite/CMakeLists.txt
+++ b/paddle/fluid/lite/CMakeLists.txt
@@ -1,17 +1,6 @@
-cc_library(executor_lite SRCS executor.cc)
-cc_library(op_lite SRCS op_lite.cc)
-cc_library(memory_lite SRCS memory.cc)
-cc_library(tensor_lite SRCS tensor.cc DEPS memory_lite)
-cc_library(variable_lite SRCS variable.cc)
-cc_library(op_registry_lite SRCS op_registry.cc)
-cc_library(scope_lite SRCS scope.cc)
-
+add_subdirectory(core)
 add_subdirectory(x86)
 add_subdirectory(cuda)
 add_subdirectory(operators)
 add_subdirectory(kernels)
 add_subdirectory(model_parser)
-
-
-# tests
-cc_test(test_scope_lite SRCS scope_test.cc DEPS scope_lite)
diff --git a/paddle/fluid/lite/core/CMakeLists.txt b/paddle/fluid/lite/core/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ddfbc83f6cbe71df7c64e226cfccd1fd73e416fa
--- /dev/null
+++ b/paddle/fluid/lite/core/CMakeLists.txt
@@ -0,0 +1,9 @@
+cc_library(executor_lite SRCS executor.cc)
+cc_library(op_lite SRCS op_lite.cc)
+cc_library(memory_lite SRCS memory.cc)
+cc_library(tensor_lite SRCS tensor.cc DEPS memory_lite)
+cc_library(variable_lite SRCS variable.cc)
+cc_library(op_registry_lite SRCS op_registry.cc)
+cc_library(scope_lite SRCS scope.cc)
+
+cc_test(test_scope_lite SRCS scope_test.cc DEPS scope_lite)
diff --git a/paddle/fluid/lite/context.cc b/paddle/fluid/lite/core/context.cc
similarity index 100%
rename from paddle/fluid/lite/context.cc
rename to paddle/fluid/lite/core/context.cc
diff --git a/paddle/fluid/lite/context.h b/paddle/fluid/lite/core/context.h
similarity index 88%
rename from paddle/fluid/lite/context.h
rename to paddle/fluid/lite/core/context.h
index 38ad0f80cdd1d835ce94362be3b2c5fa66e22127..a9908922bd8f3f277b97b7aab7de2ebc2c36989c 100644
--- a/paddle/fluid/lite/context.h
+++ b/paddle/fluid/lite/core/context.h
@@ -25,6 +25,7 @@ class Context {
  public:
   using target_wrapper_t = TargetWrapper<Target>;
   using stream_t = typename TargetWrapper<Target>::stream_t;
+  using event_t = typename TargetWrapper<Target>::event_t;
 
   Context() = default;
   Context(int device_id, stream_t compute_stream, stream_t data_stream)
@@ -35,15 +36,20 @@ class Context {
   void SetDeviceId(int device_id) { device_id_ = device_id; }
   void SetComputeStream(stream_t x) { compute_stream_ = x; }
   void SetDataStream(stream_t x) { data_stream_ = x; }
+  void SetDependEvents(const std::vector<event_t>& events) {
+    depend_events_ = events;
+  }
 
   int device_id() const { return device_id_; }
   stream_t compute_stream() const { return compute_stream_; }
   stream_t data_stream() const { return data_stream_; }
+  const std::vector<event_t>& depend_events() const { return depend_events_; }
 
  private:
-  int device_id_;
+  int device_id_{0};
   stream_t compute_stream_;
   stream_t data_stream_;
+  std::vector<event_t> depend_events_;
 };
 
 class OpContext final {
diff --git a/paddle/fluid/lite/executor.cc b/paddle/fluid/lite/core/executor.cc
similarity index 100%
rename from paddle/fluid/lite/executor.cc
rename to paddle/fluid/lite/core/executor.cc
diff --git a/paddle/fluid/lite/executor.h b/paddle/fluid/lite/core/executor.h
similarity index 100%
rename from paddle/fluid/lite/executor.h
rename to paddle/fluid/lite/core/executor.h
diff --git a/paddle/fluid/lite/op_kernel.h b/paddle/fluid/lite/core/kernel.h
similarity index 94%
rename from paddle/fluid/lite/op_kernel.h
rename to paddle/fluid/lite/core/kernel.h
index 832a257fb150cd3c0310264303aa3575b8f8cbe8..1808a0ddcd8e9397632e96959ccca2b8ae373f1b 100644
--- a/paddle/fluid/lite/op_kernel.h
+++ b/paddle/fluid/lite/core/kernel.h
@@ -19,8 +19,8 @@
 #include <map>
 #include <string>
 #include "paddle/fluid/framework/op_desc.h"
-#include "paddle/fluid/lite/context.h"
-#include "paddle/fluid/lite/target_wrapper.h"
+#include "context.h"
+#include "target_wrapper.h"
 #include "paddle/fluid/lite/utils/all.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/memory.cc b/paddle/fluid/lite/core/memory.cc
similarity index 95%
rename from paddle/fluid/lite/memory.cc
rename to paddle/fluid/lite/core/memory.cc
index 2b85d763da6b31d27a2d8c9fec30ab9a7dfbaed0..f84eeec2c09ab9983c5c9f8080e559957d174e96 100644
--- a/paddle/fluid/lite/memory.cc
+++ b/paddle/fluid/lite/core/memory.cc
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "paddle/fluid/lite/memory.h"
+#include "memory.h"
 
 namespace paddle {
 namespace framework {
diff --git a/paddle/fluid/lite/memory.h b/paddle/fluid/lite/core/memory.h
similarity index 100%
rename from paddle/fluid/lite/memory.h
rename to paddle/fluid/lite/core/memory.h
diff --git a/paddle/fluid/lite/op_lite.cc b/paddle/fluid/lite/core/op_lite.cc
similarity index 100%
rename from paddle/fluid/lite/op_lite.cc
rename to paddle/fluid/lite/core/op_lite.cc
diff --git a/paddle/fluid/lite/op_lite.h b/paddle/fluid/lite/core/op_lite.h
similarity index 78%
rename from paddle/fluid/lite/op_lite.h
rename to paddle/fluid/lite/core/op_lite.h
index 2e58dec354ceaea08c294402dcdb4e1a9d46b70c..a540fc8c83caad0fe9b64001c8556ec1c9b696ae 100644
--- a/paddle/fluid/lite/op_lite.h
+++ b/paddle/fluid/lite/core/op_lite.h
@@ -19,7 +19,7 @@
 #include <map>
 #include <string>
 #include "context.h"
-#include "op_kernel.h"
+#include "kernel.h"
 #include "paddle/fluid/framework/lod_tensor.h"
 #include "paddle/fluid/framework/op_desc.h"
 #include "paddle/fluid/framework/variable.h"
@@ -40,11 +40,13 @@ struct Registry {
  * to eliminate overhead of some operations in current framework.
  *
  * The Operator are designed as follows:
- * - it can has some members to hold the argument addresses,
- * - it should act just like a function call, no more logic should included.
+ * - it can has some members to hold the argument and some other computation
+ * resources,
+ * - it should act like a function call, no more logic included.
  */
 class OpLite : public Registry {
  public:
+  // The strategies to pick a kernel from candidates.
   enum class KernelStrategy {
     // Return the user specified one.
     kStatic = 0,
@@ -57,18 +59,25 @@ class OpLite : public Registry {
   OpLite() {}
   OpLite(std::unique_ptr<OpContext> &&x) : op_context_(std::move(x)) {}
 
+  // Check the shape.
   virtual bool CheckShape() const { return true; }
+  // Inference the outputs' shape.
   virtual bool InferShape() const { return true; }
+  // Run this operator.
   virtual bool Run() = 0;
+  // Build the operator, attach it with the runtime environment.
   virtual bool Build(const framework::OpDesc &opdesc,
                      framework::Scope *scope) = 0;
+  // Human-readable information.
   virtual std::string DebugString() const = 0;
 
+ protected:
+  // Specify the kernel to run by default.
   virtual void StaticPickKernel(
       const std::vector<TargetType> &valid_targets) = 0;
 
-  void PickBestKernel(const std::vector<TargetType> &valid_places,
-                      KernelStrategy kernel_strategy = KernelStrategy::kStatic);
+  void PickKernel(const std::vector<TargetType> &valid_places,
+                  KernelStrategy kernel_strategy = KernelStrategy::kStatic);
 
   // Create all the kernels for the valid targets.
   void CreateKernels();
diff --git a/paddle/fluid/lite/op_registry.cc b/paddle/fluid/lite/core/op_registry.cc
similarity index 100%
rename from paddle/fluid/lite/op_registry.cc
rename to paddle/fluid/lite/core/op_registry.cc
diff --git a/paddle/fluid/lite/op_registry.h b/paddle/fluid/lite/core/op_registry.h
similarity index 97%
rename from paddle/fluid/lite/op_registry.h
rename to paddle/fluid/lite/core/op_registry.h
index 1e23d58604561b1e12a3d653c74768857004ced0..3be1ee5a6d34bf53921195864aa7724de6844ac1 100644
--- a/paddle/fluid/lite/op_registry.h
+++ b/paddle/fluid/lite/core/op_registry.h
@@ -15,9 +15,9 @@
 #include <memory>
 #include <string>
 #include <unordered_map>
-#include "paddle/fluid/lite/op_kernel.h"
-#include "paddle/fluid/lite/op_lite.h"
-#include "paddle/fluid/lite/target_wrapper.h"
+#include "kernel.h"
+#include "op_lite.h"
+#include "target_wrapper.h"
 #include "paddle/fluid/lite/utils/all.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/scope.cc b/paddle/fluid/lite/core/scope.cc
similarity index 97%
rename from paddle/fluid/lite/scope.cc
rename to paddle/fluid/lite/core/scope.cc
index 1c405464e5c0497a213325beaaae056db2e52d85..6e36f72e32c7d53625d558fda6a6e3c3c8ccf4ba 100644
--- a/paddle/fluid/lite/scope.cc
+++ b/paddle/fluid/lite/core/scope.cc
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "paddle/fluid/lite/scope.h"
+#include "scope.h"
 #include "scope.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/scope.h b/paddle/fluid/lite/core/scope.h
similarity index 97%
rename from paddle/fluid/lite/scope.h
rename to paddle/fluid/lite/core/scope.h
index 11b3f23484e654c27ca73c213e0e359d93b8f9a7..56ded2b65d2f129484cfa79b64083f25560b3570 100644
--- a/paddle/fluid/lite/scope.h
+++ b/paddle/fluid/lite/core/scope.h
@@ -19,7 +19,7 @@
 #include <unordered_map>
 #include <utility>
 #include <vector>
-#include "paddle/fluid/lite/variable.h"
+#include "variable.h"
 
 namespace paddle {
 namespace lite {
diff --git a/paddle/fluid/lite/scope_test.cc b/paddle/fluid/lite/core/scope_test.cc
similarity index 96%
rename from paddle/fluid/lite/scope_test.cc
rename to paddle/fluid/lite/core/scope_test.cc
index 3e1c23172b5d5377ec81ce4a2eae8140c185799e..63c8c2f58a34680731110eb22eb144ae64ac4de8 100644
--- a/paddle/fluid/lite/scope_test.cc
+++ b/paddle/fluid/lite/core/scope_test.cc
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "paddle/fluid/lite/scope.h"
+#include "scope.h"
 #include <gtest/gtest.h>
 
 namespace paddle {
diff --git a/paddle/fluid/lite/target_wrapper.h b/paddle/fluid/lite/core/target_wrapper.h
similarity index 91%
rename from paddle/fluid/lite/target_wrapper.h
rename to paddle/fluid/lite/core/target_wrapper.h
index f7bcd3793aea04e285f026c6d691b97bac05e9bf..60de8c224db223727f62fff8f8220493af301ec7 100644
--- a/paddle/fluid/lite/target_wrapper.h
+++ b/paddle/fluid/lite/core/target_wrapper.h
@@ -19,6 +19,7 @@ namespace paddle {
 namespace lite {
 
 enum class TargetType { kHost = 0, kX86, kCUDA, kARM, kLastAsPlaceHolder };
+// Some helper macro to get a specific TargetType.
 #define TARGET(item__) paddle::lite::TargetType::item__
 #define TARGET_VAL(item__) static_cast<int>(TARGET(item__))
 
@@ -36,20 +37,22 @@ using ARM = Target<TargetType::kARM>;
 
 enum class PrecisionType { kFloat = 0, kInt8, kLastAsPlaceHolder };
 
+// Some helper macro to get a specific PrecisionType.
 #define PRECISION(item__) paddle::lite::PrecisionType::item__
 #define PRECISION_VAL(item__) static_cast<int>(PRECISION(item__))
 constexpr int kNumPrecisions =
     PRECISION_VAL(kLastAsPlaceHolder) - PRECISION_VAL(kFloat);
 
 // Event sync for multi-stream devices like CUDA and OpenCL.
+// For the devices without support of stream, leave it empty.
 template <TargetType Target>
 class Event {};
 
 // Memory copy directions.
 enum class IoDirection {
-  HtoH = 0,
-  HtoD,
-  DtoH,
+  HtoH = 0,  // Host to host
+  HtoD,      // Host to device
+  DtoH,      // Device to host
 };
 
 // This interface should be specified by each kind of target.
diff --git a/paddle/fluid/lite/tensor.cc b/paddle/fluid/lite/core/tensor.cc
similarity index 100%
rename from paddle/fluid/lite/tensor.cc
rename to paddle/fluid/lite/core/tensor.cc
diff --git a/paddle/fluid/lite/tensor.h b/paddle/fluid/lite/core/tensor.h
similarity index 100%
rename from paddle/fluid/lite/tensor.h
rename to paddle/fluid/lite/core/tensor.h
diff --git a/paddle/fluid/lite/variable.cc b/paddle/fluid/lite/core/variable.cc
similarity index 94%
rename from paddle/fluid/lite/variable.cc
rename to paddle/fluid/lite/core/variable.cc
index d086a0c7971ec7a4320d87acb0758e16fff87b9d..3ef5001f49ec70ac489431cee311f161f73fbe2e 100644
--- a/paddle/fluid/lite/variable.cc
+++ b/paddle/fluid/lite/core/variable.cc
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "paddle/fluid/lite/variable.h"
+#include "variable.h"
 
 namespace paddle {
 namespace lite {}  // namespace lite
diff --git a/paddle/fluid/lite/variable.h b/paddle/fluid/lite/core/variable.h
similarity index 96%
rename from paddle/fluid/lite/variable.h
rename to paddle/fluid/lite/core/variable.h
index bcff0aeef8b11e34571bdfc9f9d83a8024a61ef2..b7eaa9957884beadc5863b32bb4e776d7660f822 100644
--- a/paddle/fluid/lite/variable.h
+++ b/paddle/fluid/lite/core/variable.h
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #pragma once
-#include "paddle/fluid/lite/tensor.h"
+#include "paddle/fluid/lite/core/tensor.h"
 #include "paddle/fluid/lite/utils/all.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/kernels/host/fc_compute.cc b/paddle/fluid/lite/kernels/host/fc_compute.cc
index dda42ba3e1ce1a7ab83a728d66a667a4f260f763..ef0fed843c2512d132e1e02922b2f41a8559d1b0 100644
--- a/paddle/fluid/lite/kernels/host/fc_compute.cc
+++ b/paddle/fluid/lite/kernels/host/fc_compute.cc
@@ -14,7 +14,7 @@
 
 #include "paddle/fluid/lite/kernels/host/fc_compute.h"
 #include <Eigen/Core>
-#include "paddle/fluid/lite/op_registry.h"
+#include "paddle/fluid/lite/core/op_registry.h"
 
 namespace paddle {
 namespace lite {
diff --git a/paddle/fluid/lite/kernels/host/fc_compute.h b/paddle/fluid/lite/kernels/host/fc_compute.h
index 1a7e8ae74db1b93a489a7e1ac513e09918a67685..37316feba14ef1667e667a8bd572ece35a5cd79b 100644
--- a/paddle/fluid/lite/kernels/host/fc_compute.h
+++ b/paddle/fluid/lite/kernels/host/fc_compute.h
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #pragma once
-#include "paddle/fluid/lite/op_kernel.h"
+#include "paddle/fluid/lite/core/kernel.h"
 #include "paddle/fluid/lite/operators/fc_op.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/kernels/host/relu_compute.cc b/paddle/fluid/lite/kernels/host/relu_compute.cc
index e352e493877cda87cbe6c38f59d0d57358bacec7..59b9ccd836410fb3c7cfc15df924222aa767cf7c 100644
--- a/paddle/fluid/lite/kernels/host/relu_compute.cc
+++ b/paddle/fluid/lite/kernels/host/relu_compute.cc
@@ -12,4 +12,4 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "paddle/fluid/lite/kernels/relu_compute.h"
+#include "paddle/fluid/lite/kernels/host/relu_compute.h"
diff --git a/paddle/fluid/lite/kernels/host/relu_compute.h b/paddle/fluid/lite/kernels/host/relu_compute.h
index 70e19e3898b112b2e0ada2d72b362b223e8a7326..e4130e36097249c6e098017f5b6d471adcbf6bd4 100644
--- a/paddle/fluid/lite/kernels/host/relu_compute.h
+++ b/paddle/fluid/lite/kernels/host/relu_compute.h
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #pragma once
-#include "paddle/fluid/lite/op_kernel.h"
+#include "paddle/fluid/lite/core/kernel.h"
 
 namespace paddle {
 namespace lite {
diff --git a/paddle/fluid/lite/model_parser/model_parser.cc b/paddle/fluid/lite/model_parser/model_parser.cc
index 59b518fb28069fc91395a8571653f7ab2315adcc..9b5e676fa12396238b45ad90a5169c681f9eceb2 100644
--- a/paddle/fluid/lite/model_parser/model_parser.cc
+++ b/paddle/fluid/lite/model_parser/model_parser.cc
@@ -14,9 +14,9 @@
 
 #include "paddle/fluid/lite/model_parser/model_parser.h"
 #include <fstream>
-#include "paddle/fluid/lite/scope.h"
-#include "paddle/fluid/lite/tensor.h"
-#include "paddle/fluid/lite/variable.h"
+#include "paddle/fluid/lite/core/scope.h"
+#include "paddle/fluid/lite/core/tensor.h"
+#include "paddle/fluid/lite/core/variable.h"
 
 namespace paddle {
 namespace lite {
diff --git a/paddle/fluid/lite/operators/fc_op.cc b/paddle/fluid/lite/operators/fc_op.cc
index 245941832b2f725afde0803383154c6a7fa2f8a3..827e921bb8fd0673a5061c48bbc72c19658dadda 100644
--- a/paddle/fluid/lite/operators/fc_op.cc
+++ b/paddle/fluid/lite/operators/fc_op.cc
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #include "fc_op.h"
-#include "paddle/fluid/lite/op_registry.h"
+#include "paddle/fluid/lite/core/op_registry.h"
 
 namespace paddle {
 namespace lite {
diff --git a/paddle/fluid/lite/operators/fc_op.h b/paddle/fluid/lite/operators/fc_op.h
index 1f07f434f5ba2d728dcb1fe3d7946cd7ccff88db..f3a1eaca92b3d5f40c4f0ce7b83cef8b36e846a3 100644
--- a/paddle/fluid/lite/operators/fc_op.h
+++ b/paddle/fluid/lite/operators/fc_op.h
@@ -14,8 +14,8 @@
 
 #include <string>
 #include <vector>
-#include "paddle/fluid/lite/op_lite.h"
-#include "paddle/fluid/lite/tensor.h"
+#include "paddle/fluid/lite/core/op_lite.h"
+#include "paddle/fluid/lite/core/tensor.h"
 #include "paddle/fluid/lite/utils/all.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/operators/relu_op.cc b/paddle/fluid/lite/operators/relu_op.cc
index 675acf61d130df7cc78ceba8574f8a5deb73e49a..189cc16b1c6c151a3dc5bc12c91876475def53d9 100644
--- a/paddle/fluid/lite/operators/relu_op.cc
+++ b/paddle/fluid/lite/operators/relu_op.cc
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #include "paddle/fluid/lite/operators/relu_op.h"
-#include "paddle/fluid/lite/op_registry.h"
+#include "paddle/fluid/lite/core/op_registry.h"
 
 namespace paddle {
 namespace lite {
diff --git a/paddle/fluid/lite/operators/relu_op.h b/paddle/fluid/lite/operators/relu_op.h
index 0a9a6c9399c3ce1e5eb32cc34586b3c705fafce7..b2c32f530fdada81aa97e08a3777c95a93a5a6b0 100644
--- a/paddle/fluid/lite/operators/relu_op.h
+++ b/paddle/fluid/lite/operators/relu_op.h
@@ -14,8 +14,8 @@
 
 #include <string>
 #include <vector>
-#include "paddle/fluid/lite/op_lite.h"
-#include "paddle/fluid/lite/tensor.h"
+#include "paddle/fluid/lite/core/op_lite.h"
+#include "paddle/fluid/lite/core/tensor.h"
 #include "paddle/fluid/lite/utils/all.h"
 
 namespace paddle {
diff --git a/paddle/fluid/lite/x86/target_wrapper.h b/paddle/fluid/lite/x86/target_wrapper.h
index f105f4af83b76520e664e76ff567bbffa968c11f..222eb80f7f39ce42d9ff2a5cf5e4a9b7c1b4e364 100644
--- a/paddle/fluid/lite/x86/target_wrapper.h
+++ b/paddle/fluid/lite/x86/target_wrapper.h
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #pragma once
-#include "paddle/fluid/lite/target_wrapper.h"
+#include "paddle/fluid/lite/core/target_wrapper.h"
 
 namespace paddle {
 namespace framework {