Error while compiling Caffe

Question

I am trying to compile Caffe with OpenBLAS in Ubuntu 16.04. I had downloaded and compile OpenBLAS with make NO_AFFINITY=1 USE_OPENMP=1 OpenBLAS compilation is fine and all its tests are also run

OpenBLAS build complete. (BLAS CBLAS LAPACK LAPACKE)
 OS ... Linux 
 Architecture ... x86_64 
 BINARY ... 64bit 
 C compiler ... GCC (command line : gcc)
 Fortran compiler ... GFORTRAN (command line : gfortran)
 Library Name ... libopenblas_sandybridgep-r0.2.20.dev.a (Multi threaded; Max num-threads is 4)
 Use OpenMP in the multithreading. Because of ignoring OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS flags, 
 you should use OMP_NUM_THREADS environment variable to control the number of threads.

However linking with OpenBLAS libs in Caffe install is giving the following error

Linking CXX executable upgrade_net_proto_binary /opt/OpenBLAS/lib/libopenblas.so: undefined reference to `GOMP_parallel@GOMP_4.0' collect2: error: ld returned 1 exit status tools/CMakeFiles/upgrade_net_proto_binary.dir/build.make:129: recipe for target 'tools/upgrade_net_proto_binary' failed make[2]: * [tools/upgrade_net_proto_binary] Error 1 CMakeFiles/Makefile2:403: recipe for target 'tools/CMakeFiles/upgrade_net_proto_binary.dir/all' failed make[1]: * [tools/CMakeFiles/upgrade_net_proto_binary.dir/all] Error 2

• Alex Punnen: installing libatlas-base-dev and using this instead of BLAS helped in getting over above; still like to know why

Answer 1

Most likely the reason is that you're linking to the compiled OpenBLAS instead of installing it and linking to the installation. After you run make, you should run make install PREFIX=/path/to/install/OpenBLAS, and then you should link to the installed version.

• Alex Punnen: I had installed it via make install