c ++并链接到lapack

Question

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

Answer 1

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.

Answer 2

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.

Answer 3

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. :-)

Answer 4

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.