Mercurial > octave
changeset 21423:e169fe73b57e stable
svds.m: Special handling for case of sigma=0 (bug #46683).
* svds.m: If ARPACK does not return the correct number of positive eigenvalues,
then use the negative eigenvalues instead.
| author | Marco Caliari <marco.caliari@univr.it> |
|---|---|
| date | Mon, 28 Dec 2015 08:40:05 -0800 |
| parents | 2e21387ce06b |
| children | a3542f00c993 7bb71bf2f30f |
| files | scripts/sparse/svds.m |
| diffstat | 1 files changed, 8 insertions(+), 0 deletions(-) [+] |
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--- a/scripts/sparse/svds.m Thu Mar 03 09:27:04 2016 -0800 +++ b/scripts/sparse/svds.m Mon Dec 28 08:40:05 2015 -0800 @@ -200,6 +200,14 @@ ## less than or equal to zero to within some tolerance scaled by the ## norm since if we don't we might end up with too many singular ## values. + if (b_sigma == 0) + if (sum (s>0) < k) + ## It may happen that the number of positive s is less than k. + ## In this case, take -s (if s in an eigenvalue, so is -s), + ## flipped upside-down. + s = flipud (-s); + endif + endif tol = norma * opts.tol; ind = find (s > tol); if (length (ind) < k)