Re: [igraph] Trouble with arpack

[Gabor Csardi]

David,

you're right, this is a bug. I don't know how much testing 
will be done before the next release, but i'll correct the classic 
eigenvalue solver for sure (i.e. the mode=1 case). It seems to be 
a small bug, we don't copy the output of the internal ARPACK 
solver correctly if the eigenvalue is complex. 

Thanks,
G.

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On Wed, Apr 16, 2008 at 06:17:47PM +0200, David Morton wrote:
> Hi,
> I ran into trouble using arpack
> with non-symmetric matrices. E.g.
> 
>   A <- matrix(runif(16,-1,1),4) 
>   fct <- function(x,extra=NULL)A %*% x
>   arpack(fct, options=list(n=ncol(A), nev=1, ncv=3), sym=FALSE)
> 
> generaly outputs eigenvectors that don't solve the aigenvalue equation Av=lv,
> where l seems to correspond to the results obtained with eigen().
> Is a full testing of arpack() planned in a near future?
> 
> Anyway, igraph is just a great piece of software!
> Bravo!
> 
> 
> --
> David Morton de Lachapelle

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-- 
Csardi Gabor <address@hidden>    UNIL DGM