Using ARPACK in Julia

[Christopher Wong]

Hi, I'm just starting out in Julia. Is there any documentation currently on how to use Julia's implementations of ARPACK? I was recently told I don't need to load the LinAlg libraries, so I tried calling a typical function in ARPACK like "saupd" but it didn't recognize it.

Can anybody step me through how to use those lirbaries?

Thanks again.

[Steven G. Johnson]

You would normally call the high-level "eigs" function (similar to Matlab), which is a wrapper around ARPACK:

    http://docs.julialang.org/en/release-0.1/stdlib/linalg/?highlight=eigs#eigs

The documentation for this function isn't very good right now, unfortunately, but it is modeled after the Matlab eigs function:

    http://www.mathworks.com/help/matlab/ref/eigs.html

The eigs function automatically detects if the matrix is real-symmetric and calls saupd in that case (see the source code in julia/base/linalg/arpack.jl and julia/base/linalg/arnoldi.jl)

[Viral Shah]

That's right. The eigs and svds functions are wrappers around ARPACK. The implementations are not complete, but it is fairly easy to finish the rest of the functionality.

https://github.com/JuliaLang/julia/issues/2956

The ARPACK functions are all wrapped in julia. See base/linalg/arpack.jl for the wrappers, and base/linalg/arnoldi.jl for example usage. They are accessible as Base.LinAlg.dnaupd and such. If you are familiar with ARPACK, it would be great to have contributions to complete the eigs and svds interfaces in #2956.

-viral