CODEWITHSUNDEEP
c++compilationlinkerlapack
physiker
physiker

Reputation: 919

c++ and link to lapack

I have several files which I need to compile together as following in my makefile (names are dummy now):

compile:
        g++ prog1.cpp func1.cpp func2.cpp func3.cpp -L/usr/lib/ -lmkl_lapack64 -lmkl 
        -lguide -lpthread -o output_ready.out

When I do make compile, then I get the following errors:

/usr/bin/ld: cannot find -lmkl_lapack64                                                                                                                                                
/usr/bin/ld: cannot find -lmkl                                                                                                                                                         
/usr/bin/ld: cannot find -lguide                                                                                                                                                       
collect2: ld returned 1 exit status                                                                                                                                                    
make: *** [compile] Error 1

This program was correctly compiled in another machine previously.

Q: How can I check the path for lapack lib if they are correct? How should I fix them? The libraries are installed (not sure if with the right path).

Any helpful comment is highly appreciated. R

Upvotes: 1

Views: 3191

Answers (4)

Ehsan
Ehsan

Reputation: 400

An excellent way to find the correct compiler and linker flags based on your OS, architecture, etc. is using the Intel online tool, which you can find here:

https://software.intel.com/en-us/articles/intel-mkl-link-line-advisor.

To access it, you need to login to the Intel website.

Upvotes: 0

Eugene B
Eugene B

Reputation: 1013

First of all I would have suggested you to check if libraries are installed in correct directories, as you planned yourself. An obvious way to do this is just to cd /usr/lib and see whether there are any lapack libraries (you will notice them at once).

If everything is installed where it should have been, I would suggest you to compile with

-I /usr/local/include/lapackpp/

for headers, and

-L /usr/local/lib -llapackpp

for libraries, as all lapack libraries should be accessed through it.

Also, are you sure you want to look for libraries in /usr/lib, but not in /usr/local/lib? I guess this is OS/settings specific, though.

Finally, some time ago I have had similar problem to the one you have and found a good and explicit explanation on this website. :-)

Upvotes: 1

Dave Rager
Dave Rager

Reputation: 8160

I don't think you need -L/usr/lib as I believe the compiler already knows to look there for libraries. That said, you do need -L<path to where lapack libraries are> if they were not installed in a standard location.

Upvotes: 1

Arne Mertz
Arne Mertz

Reputation: 24626

The only path where he looks for the lapack libs is /usr/lib - since that's the only dircetory you specified for the linker. If the libs are installed in another location you will have to find it out and

  • provide that location to the linker via another -L parameter,
  • or move the libs to /usr/lib

so the linker can find the libs.

Upvotes: 1

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