I am trying to run Eigen in parallel.
I have usual sequential code with Eigen which is compiled and works perfectly. I am trying to test it with "-fopenmp" flag (I don't have any parallel loops inside my code, just want to test Eigen with OpenMP): but then the compiler gives me a linker error:

Code: Select all

Undefined symbols for architecture x86_64:

Additional info: GCC 4.8.2 and Os X 10.9.2.
flags which I am using are: "-std=c++11 -g -fopenmp -Wall -Wextra -pthread -Wno-missing-field-initializers"
also "Eigen/Core" is included.

Thank you in advance.

What are the undefined symbols?

ggael wrote:What are the undefined symbols?

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Undefined symbols for architecture x86_64:
  "_GOMP_parallel", referenced from:
      void Eigen::internal::parallelize_gemm<true, Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> >, long>(Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> > const&, long, long, bool) in LinearSolver.cpp.o
  "_omp_get_max_threads", referenced from:
      Eigen::internal::manage_multi_threading(Eigen::Action, int*) in LinearSolver.cpp.o
  "_omp_get_num_threads", referenced from:
      void Eigen::internal::parallelize_gemm<true, Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> >, long>(Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> > const&, long, long, bool) [clone ._omp_fn.0] in LinearSolver.cpp.o
      void Eigen::internal::parallelize_gemm<true, Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> >, long>(Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> > const&, long, long, bool) in LinearSolver.cpp.o
      Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>::run(long, long, long, double const*, long, double const*, long, double*, long, double, Eigen::internal::level3_blocking<double, double>&, Eigen::internal::GemmParallelInfo<long>*) in LinearSolver.cpp.o
  "_omp_get_thread_num", referenced from:
      void Eigen::internal::parallelize_gemm<true, Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> >, long>(Eigen::internal::gemm_functor<double, long, Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1> const, 0, Eigen::OuterStride<-1> >, Eigen::Map<Eigen::Matrix<double, -1, -1, 0, -1, -1>, 0, Eigen::OuterStride<-1> >, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::internal::gemm_blocking_space<0, double, double, -1, -1, -1, 1, false> > const&, long, long, bool) [clone ._omp_fn.0] in LinearSolver.cpp.o
      Eigen::internal::general_matrix_matrix_product<long, double, 0, false, double, 0, false, 0>::run(long, long, long, double const*, long, double const*, long, double*, long, double, Eigen::internal::level3_blocking<double, double>&, Eigen::internal::GemmParallelInfo<long>*) in LinearSolver.cpp.o
ld: symbol(s) not found for architecture x86_64

Also I updated GCC to 4.9

You need to add -fopenmp to the linker flags too.