# R-alpha: Eigenvalue Computation Query

**Kurt Hornik
**
Kurt.Hornik@ci.tuwien.ac.at

*Tue, 20 May 1997 08:18:22 +0200*

>>>>>* Ross Ihaka writes:
*
>* I have been looking at the "eigen" function and have reintroduced the
*>* ability to compute (right) eigenvalues and vectors for non-symmetric
*>* matrices. I've also made "eigen" complex capable.
*
>* The code is based on the eispack entry points RS, RG, CH, CG (which is
*>* what S appears to use too). The problem with both the S and R
*>* implementations is that they consume huge amounts of memory. Some of
*>* this is due to purely ".Fortran" overhead, which I think I can cure.
*>* But some of the bloat is due to the inclusion of special eigenvalues-only
*>* code from eispack.
*
>* The question is:
*
>* Should I drop this special code and always compute both eigenvalues
*>* and eigenvectors? This would substantially reduce code size, but might
*>* increase computational cost in the case where only eigenvalues are
*>* needed.
*
I'd say, reduce code size.
-k
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