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Re: [igraph] Trouble with arpack

From: Gabor Csardi
Subject: Re: [igraph] Trouble with arpack
Date: Thu, 17 Apr 2008 08:59:25 +0200
User-agent: Mutt/1.5.13 (2006-08-11)


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. 


ps. if you don't write from the address you used to sign up, 
then your mails will be delayed.... you can sign up for both 
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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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> igraph-help mailing list
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Csardi Gabor <address@hidden>    UNIL DGM

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