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error message about "eigs" function

Asked by Chong Hou on 3 Feb 2012
Latest activity Edited by Matt J
on 27 Sep 2013

I use function eigs(A,1,'sm') in my code, and when I run it, sometimes there is the error message saying "Error using eigs (line 254) Error with ARPACK routine dnaupd: info = -9". What does that mean? Thanks!

The matrix A is a real symmetric matrix in my code, though sometimes it might be singular.


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1 Answer

Answer by Walter Roberson
on 3 Feb 2012

c  INFO    Integer.  (INPUT/OUTPUT)
c          Error flag on output.
c          = -9: Starting vector is zero.

This could occur if you supplied an options structure to eigs() and the v0 (starting column vector) field was all zero.


Thank you Walter! Could you be more specific? Does the "v0 field" mean the first column of my matrix A?

No, the v0 field is a structure field named v0.

If you look at the possible syntaxes for eigs(), it lists,


In those situations, opts is a structure, and the v0 field would be a field in that structure.

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