Re: Issues with eigs

[Manav Bhatia]

Please see the discussion here: https://github.com/opencollab/arpack-ng/issues/149#issuecomment-419715128

We were able to identify this to be a bug in lapack that was fixed in lapack v 3.6.

System lapack on Mac provided through the Accelerate framework is an older version of lapack and still has the bug. So, the solution is to replace it with a newer version of lapack. 

I replaced this with arpack that links to lapack v 3.8 and am able to get expected results. 

On a related note, is the macport build of octave handled by someone on this mailing list? 

If so, I would recommend creating a variant to use lapack installed via macports. Currently the only two variants that exist are accelerate and atlas. Even with atlas, I suspect that the routines not provided by atlas will come from system lapack. 

-Manav

On Sep 7, 2018, at 9:16 AM, Manav Bhatia <address@hidden> wrote:

Thanks for looking into this. I am running on Mac OS with octave installed through macports. 

Following are the outputs on my machine. 

octave:4> eigs(m1, m0)

error: __eigs__: eigs: error -8 in dnaupd

error: called from

    eigs at line 285 column 18

octave:4> version

ans = 4.4.1

octave:5> which eigs

'eigs' is a function from the file /opt/local/share/octave/4.4.1/m/sparse/eigs.m

octave:6> 

Thanks,

Manav

On Sep 7, 2018, at 8:13 AM, Juan Pablo Carbajal <address@hidden> wrote:

Hi,

I can't reproduce in 4.4.0, which Octave version are you using? What OS?

eigs(m1,m0)

ans =

        0.00032 - 2672312.38464i
        0.00032 + 2672312.38464i
        0.00004 - 2639857.10699i
        0.00004 + 2639857.10699i
        0.00010 + 2587664.34543i
        0.00010 - 2587664.34543i

version

ans = 4.4.0

which eigs

'eigs' is a function from the file /usr/local/share/octave/4.4.0/m/sparse/eigs.m

On Fri, Sep 7, 2018 at 3:02 PM Manav Bhatia <address@hidden> wrote:

Hi,

  I have a set of matrices, M0 and M1 (attached), obtained from numerical discretization of a beam problem.

  I am attempting to solve the eigenproblem    M1 x = lambda M0 x .

  Computing this with the following works fine:

m0 = load(‘M0.txt’); m1 = load(‘M1.txt’);
eig( m1, m0)

   However, using eigs( m1, m0) throws the following error:
error: __eigs__: eigs: error -8 in dnaupd
error: called from
   eigs at line 285 column 18

   I am not sure what could be causing this. Any guidance will be appreciated.

Thanks,
Manav