How To: Referencing LAPACK library from FORTRAN 95 in Cygwin

Question

I have a FORTRAN 95 program that needs to make some calls to the LAPACK library. I recently found out that Cygwin because it can install LAPACK as an extra option.

Well, LAPACK exists in the /lib/lapack/ directory as "cyglapack.dll". Having only a very informal training in Fortran programming, I have no idea how to reference a .dll library as opposed to a .mod module.

Any suggestions or directions to articles answering my question are GREATLY appreciated! (P.S. I did search first.. I don't think I know the proper terms to get a useful article.)

Answer 1

Conceptually calling Lapack should be as easy as calling any other DLL. You just have to figure out what link flags and statements to include in your build statement(s).

From Fortran you would, probably, declare as EXTERNAL the functions from Lapack that you wan't to use. This tells the compiler not to bother looking for a definition of the function in your sources, or in a mod file, but that the definition will be provided at link time. This is where the fun begins, as you try to ensure that the signatures of your calls match the signatures expected by the DLL.

I might be able to provide more help if you provide more information. What is your Windows development environment ? What Fortran compiler are you using ? What compile and link tools are you using ? What does your current link statement look like ?

Answer 2

Search terms: dynamic linking fortran

Take a look at this page:

http://sources.redhat.com/ml/binutils/2001-12/msg00471.html

It mentions using dlltool to generate a .a file from a .dll file. Presumably you should be able to link to that in the normal way (usually a lib switch on the compile command).

Otherwise, consider running a linux Live CD for the sake of avoiding the problem in the first place! If you're a student or an academic, see if you can find a server with fortran installed (the IT staff are usually pretty helpful) where you can compile and run your program.