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Thread Subject:
Error in using eigs function

Subject: Error in using eigs function

From: Payel Chatterjee

Date: 21 Dec, 2012 21:25:19

Message: 1 of 5

I am trying to find only those eigenvalues for sparse matrix which are not infinte in values. For this purpose I used eigs function and did an inverse iteration to get only first few eigenvalues.
However, I am getting this error:
Error with ARPACK routine dsaupd: info = -9999
Am I doing anything wrong somewhere conceptually. What does this error mean?
Please suggest.
Thanks

Subject: Error in using eigs function

From: Nasser M. Abbasi

Date: 22 Dec, 2012 00:46:14

Message: 2 of 5

On 12/21/2012 3:25 PM, Payel Chatterjee wrote:
> I am trying to find only those eigenvalues for sparse matrix which are not infinte
>in values. For this purpose I used eigs function and did an inverse iteration to get
>only first few eigenvalues.
> However, I am getting this error:
> Error with ARPACK routine dsaupd: info = -9999
> Am I doing anything wrong somewhere conceptually. What does this error mean?
> Please suggest.
> Thanks
>

from:

http://www.caam.rice.edu/software/ARPACK/UG/node136.html

c = -9999: Could not build an Arnoldi factorization.
c IPARAM(5) returns the size of the current Arnoldi
c factorization. The user is advised to check that
c enough workspace and array storage has been allocated.



--Nasser

Subject: Error in using eigs function

From: Roger Stafford

Date: 22 Dec, 2012 00:50:22

Message: 3 of 5

"Payel Chatterjee" wrote in message <kb2k3v$3ml$1@newscl01ah.mathworks.com>...
> I am trying to find only those eigenvalues for sparse matrix which are not infinte in values. For this purpose I used eigs function and did an inverse iteration to get only first few eigenvalues.
> However, I am getting this error:
> Error with ARPACK routine dsaupd: info = -9999
> Am I doing anything wrong somewhere conceptually. What does this error mean?
> Please suggest.
> Thanks
- - - - - - - - - - -
  The eigenvalues of a matrix are the roots of its characteristic polynomial. These polynomials may have complex-valued roots or repeated roots, but never infinite roots, and hence a matrix (with finite elements) cannot have infinite eigenvalues. It is true that a singular matrix will have one or more zero eigenvalues, but its inverse does not exist, so it is meaningless to speak of its inverse's infinite-valued eigenvalues. Therefore I do not understand what you mean by "an inverse iteration". If you start with a matrix which possesses an inverse, the matrix can have neither zero eigenvalues nor infinite eigenvalues and therefore neither can its inverse.

Roger Stafford

Subject: Error in using eigs function

From: Bruno Luong

Date: 22 Dec, 2012 08:14:12

Message: 4 of 5

"Roger Stafford" wrote in message <kb304e$ckj$1@newscl01ah.mathworks.com>...
>herefore I do not understand what you mean by "an inverse iteration". If you start with a matrix which possesses an inverse, the matrix can have neither zero eigenvalues nor infinite eigenvalues and therefore neither can its inverse.

Roger, inverse iteration is the method that does this iteration:

x_{n+1} = inv(A - lambda I) * x_{n}
where lambda is a fix input parameter, I is identity matrix.

It converges to the pair eigenvector/eigenvalue having the value closest to the parameter lambda.

Bruno

Subject: Error in using eigs function

From: Bruno Luong

Date: 22 Dec, 2012 08:17:17

Message: 5 of 5

"Payel Chatterjee" wrote in message <kb2k3v$3ml$1@newscl01ah.mathworks.com>...
> I am trying to find only those eigenvalues for sparse matrix which are not infinte in values. For this purpose I used eigs function and did an inverse iteration to get only first few eigenvalues.
> However, I am getting this error:
> Error with ARPACK routine dsaupd: info = -9999
> Am I doing anything wrong somewhere conceptually. What does this error mean?
> Please suggest.

You are not necessary doing anything wrong. This function from ARPACk sometime fails on its own. This is my experience.

Bruno

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