add cmake external project for eigen

CMakeLists.txt

@@ -92,6 +92,7 @@ include(external/openblas)  # download, build, install openblas
 include(external/swig)      # download, build, install swig
 include(external/warpctc)   # download, build, install warpctc
 include(external/any)       # download libn::any
+include(external/eigen)     # download eigen3
 
 include(generic)            # simplify cmake module
 include(package)            # set paddle packages

cmake/external/eigen.cmake

@@ -0,0 +1,20 @@
+INCLUDE(ExternalProject)
+
+SET(EIGEN_SOURCE_DIR ${THIRD_PARTY_PATH}/eigen3)
+
+INCLUDE_DIRECTORIES(${EIGEN_SOURCE_DIR}/src/)
+
+ExternalProject_Add(
+    eigen3
+    ${EXTERNAL_PROJECT_LOG_ARGS}
+    URL            "https://bitbucket.org/eigen/eigen/get/f3a22f35b044.tar.gz"
+    URL_MD5        "4645c66075982da6fa0bcf6b20f3e8f7"
+    PREFIX          ${EIGEN_SOURCE_DIR}
+    UPDATE_COMMAND  ""
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND     ""
+    INSTALL_COMMAND   ""
+    TEST_COMMAND      ""
+)
+
+LIST(APPEND external_project_dependencies eigen3)

paddle/framework/ddim_test.cc

@@ -1,6 +1,9 @@
 #include <sstream>
 #include <vector>
 
+#include "eigen3/Eigen/Core"
+#include "eigen3/Eigen/Dense"
+#include "eigen3/unsupported/Eigen/CXX11/Tensor"
 #include "gtest/gtest.h"
 #include "paddle/framework/ddim.h"
 
@@ -61,3 +64,44 @@ TEST(DDim, Print) {
   ss << ddim;
   EXPECT_EQ("2, 3, 4", ss.str());
 }
+
+template <typename T>
+using Vec =
+    Eigen::TensorMap<Eigen::Tensor<T, 1, Eigen::RowMajor, Eigen::DenseIndex>,
+                     Eigen::Aligned>;
+
+template <typename T>
+using Matrix =
+    Eigen::TensorMap<Eigen::Tensor<T, 2, Eigen::RowMajor, Eigen::DenseIndex>,
+                     Eigen::Aligned>;
+
+template <typename T>
+void print(T* input, int size) {
+  for (int i = 0; i < size; i++) {
+    std::cout << input[i] << " ";
+  }
+  std::cout << std::endl;
+}
+
+TEST(Eigen, start) {
+  int size = 4;
+
+  float* t_a = (float*)malloc(size * sizeof(float));
+  float* t_b = (float*)malloc(size * sizeof(float));
+  float* t_c = (float*)malloc(size * sizeof(float));
+  for (int i = 0; i < size; i++) {
+    t_a[i] = i;
+    t_b[i] = i;
+  }
+  Vec<float> a(t_a, size);
+  Vec<float> b(t_b, size);
+  Vec<float> c(t_c, size);
+
+  Eigen::DefaultDevice dd;
+  c.device(dd) = a + b;
+  print<float>(t_c, size);
+
+  free(t_a);
+  free(t_b);
+  free(t_c);
+}