topic Quote:Jing X. (Intel) wrote: in Intel® oneAPI Math Kernel Library

Undefined references to mkl objects

Sresht__Vishnu — Sun, 12 Feb 2017 17:10:30 GMT

I'm attempting to compile OpenCV with Intel MKL 2017.0 on Ubuntu 16.04.1 with , but I keep running up against the following errors at compile time:

/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_spblas_lp64_ccsr0ttluc__svout_seq'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_intel_lp64.so: undefined reference to `mkl_lapack_zlantp'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_spblas_sdia1ttluf__mvout_par'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_spblas_lp64_ccsr1ntuuf__mvout_par'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_blas_xdgemv'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_spblas_ccsr1ntuuf__smout_par'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_sparse_d_csr_ng_n_spmmd_ker_i4'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_spblas_ccoo0nhluc__mvout_par'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_sequential.so: undefined reference to `mkl_spblas_lp64_dcsr1ttluf__svout_seq'
/opt/intel/compilers_and_libraries_2017.1.132/linux/mkl/lib/intel64_lin/libmkl_intel_lp64.so: undefined reference to `mkl_lapack_dgelsd'

I have installed Intel MKL and I have the following in my zsh startup script:

source /opt/intel/mkl/bin/mklvars.sh intel64

I also have the following in /etc/ld.so.conf.d/intel_mkl.conf :

/opt/intel/lib/intel64
/opt/intel/mkl/lib/intel64

CMake manages to find MKL and reports:

-- Found MKL 2017.0.1 at: /opt/intel/mkl
-- LAPACK(MKL): LAPACK_LIBRARIES: /opt/intel/mkl/lib/intel64/libmkl_core.so;/opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so;/opt/intel/mkl/lib/intel64/libmkl_sequential.so;/opt/intel/mkl/lib/intel64/libmkl_core.so;/opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so;/opt/intel/mkl/lib/intel64/libmkl_sequential.so;/opt/intel/mkl/lib/intel64/libmkl_core.so;/opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so;/opt/intel/mkl/lib/intel64/libmkl_sequential.so;-lpthread;-lm;-ldl
-- LAPACK(MKL): Support is enabled.

CMake also lists:

--     Use Intel VA-API/OpenCL:     NO
--     Use Lapack:                  YES (/opt/intel/mkl/lib/intel64/libmkl_core.so /opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so /opt/intel/mkl/lib/intel64/libmkl_sequential.so /opt/intel/mkl/lib/intel64/libmkl_core.so /opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so /opt/intel/mkl/lib/intel64/libmkl_sequential.so /opt/intel/mkl/lib/intel64/libmkl_core.so /opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so /opt/intel/mkl/lib/intel64/libmkl_sequential.so -lpthread -lm -ldl)
--     Use Eigen:                   NO
--     Use Cuda:                    YES (ver 8.0)
--     Use OpenCL:                  YES

What am I missing? Are there any additional compile flags I should be specifying?

Hi,

Jing_Xu — Mon, 13 Feb 2017 06:21:33 GMT

Hi,

Could you store the following 3 when compiling OpenCV against MKL, and then share with us?

1. history of commands, step-by-step.

2. environment variables (before execution of cmake). They could be exported to file with the following command on Linux: env > filename.

3. cmake history. They could be redirected to file with the following command on Linux: cmake ......... 2>&1 | tee filename.

Hi

kobe_y_ — Tue, 14 Feb 2017 07:32:21 GMT

I have the same problem, I just workaround by add flag "-D WITH_LAPACK=OFF".

Quote:Jing X. (Intel) wrote:

Sresht__Vishnu — Fri, 17 Feb 2017 04:48:58 GMT

Jing X. (Intel) wrote:

Hi,

Could you store the following 3 when compiling OpenCV against MKL, and then share with us?

1. history of commands, step-by-step.

2. environment variables (before execution of cmake). They could be exported to file with the following command on Linux: env > filename.

3. cmake history. They could be redirected to file with the following command on Linux: cmake ......... 2>&1 | tee filename.

Hi Jing,

Here's what I did:

Installed MKL using the instructions here: https://software.intel.com/en-us/articles/intel-mkl-113-install-guide
Added the following to (a new) file /etc/ld.so.conf.d/intel_mkl.conf:
/opt/intel/lib/intel64
/opt/intel/mkl/lib/intel64
Added the following to my .zshrc file:
source /opt/intel/mkl/bin/mklvars.sh intel64
Clone the OpenCL repository at https://github.com/opencv/opencv.git
Clone the OpenCL extras repository at https://github.com/opencv/opencv_contrib.git
Run CMAKE from within a freshly created 'release' directory within the cloned opencv repository:

cd opencv

mkdir release

cd release

cmake -D CMAKE_BUILD_TYPE=RELEASE \

      -D CMAKE_INSTALL_PREFIX=/opt/opencv \

      -D WITH_CUDA=ON \

      -D ENABLE_FAST_MATH=1 \

      -D CUDA_FAST_MATH=1 \

      -D WITH_CUBLAS=1 .. \

      -D INSTALL_PYTHON_EXAMPLES=ON \

      -D WITH_OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib/modules \

      -D WITH_TBB=ON \

      -D BUILD_NEW_PYTHON_SUPPORT=ON \

      -D WITH_V4L=ON \

      -D INSTALL_C_EXAMPLES=ON \

      -D BUILD_EXAMPLES=ON \

      -D WITH_QT=ON \

      -D WITH_OPENGL=ON \

      .. 2>&1 | tee build_output.log
make -j8 > >(tee make_output.log) 2> >(tee make_errors.log >&2)
ERROR

I have attached files listing my environment variables, cmake output, build output and build errors to this post. I hope they help you help me figure out what's going on!

Quote:kobe yu wrote:

Sresht__Vishnu — Fri, 17 Feb 2017 05:24:48 GMT

kobe yu wrote:

Hi

I have the same problem, I just workaround by add flag "-D WITH_LAPACK=OFF".

Hi Kobe,

That's an excellent idea and it totally works! However, I would still like to know why I'm unable to link Intel's lapack to OpenCV and I'm hoping you, or someone else, can help me figure this out.

I found a fix that allows you

Sresht__Vishnu — Mon, 20 Feb 2017 04:00:00 GMT

I found a fix that allows you to compile OpenCV using MKL.

All of those undefined references were references to objects in libmkl_core.so. Even though this library is specified in the link line, gcc on Ubuntu 16.04 doesn't look inside it when searching for these items.

The fix was to specify -Wl,--no-as-needed in the link line before the Intel MKL libraries. This can be accomplished in a CMAKE-based project by setting the variable CMAKE_SHARED_LINKER_FLAGS_RELEASE:STRING=-Wl,--no-as-needed in CMakeCache.txt

Great to hear that.

Jing_Xu — Mon, 20 Feb 2017 05:08:12 GMT

Great to hear that.

Thank you for sharing the solution.

Hi Vishnu,

Ying_H_Intel — Mon, 20 Feb 2017 05:12:00 GMT

Hi Vishnu,

thanks much for the sharing. We can't reproduce the problem under Linux. But the issue do related to the system and mkl library.

all unreferenced symbols like mkl_lapack_zlantp are defined in libmkl_core.so

[yhu5_new@hsw-ep01 cmake]$ nm /opt/intel/mkl/lib/intel64/libmkl_core.so |grep mkl_lapack_zlantp
0000000000a14d20 T mkl_lapack_zlantp

"libmkl_intel_lp64 libmkl_sequential libmkl_core " are supposed to be used together and here in the link line, the combination were repeated several times, but miss mkl_core at last one.

opt/intel/mkl/lib/intel64/libmkl_core.so;/opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so;/opt/intel/mkl/lib/intel64/libmkl_sequential.so;/opt/intel/mkl/lib/intel64/libmkl_core.so;/opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so;/opt/intel/mkl/lib/intel64/libmkl_sequential.so;/opt/intel/mkl/lib/intel64/libmkl_core.so;/opt/intel/mkl/lib/intel64/libmkl_intel_lp64.so;/opt/intel/mkl/lib/intel64/libmkl_sequential.so;-lpthread;-lm;-ldl

So It seems there is some problem in FINDLAPACK.cmake processing( OpenCVFindMKL.cmake). the fix is CMAKE_SHARED_LINKER_FLAGS_RELEASE:STRING=-Wl,--no-as-needed

or like the article https://software.intel.com/en-us/articles/symbol-lookup-error-when-linking-intel-mkl-with-gcc-on-ubuntu

If possible, could you please try Set environment variable >export LD_PRELOAD=/path/to/libmkl_core.so and see if it can work around?

Thanks

Ying

Hi Ying,

Sresht__Vishnu — Sun, 26 Feb 2017 02:02:09 GMT

Hi Ying,

Thank you for that alternate solution. Yes, setting LD_PRELOAD=/path/to/libmkl_core.so also works. So apparently, there is some issue when it comes to the combination of gcc, mkl, and ubuntu. Fortunately the two workarounds above seem to work.