[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Octave-bug-tracker] [bug #29487] Feature request: svd with 3 output var
|
From: |
Jaroslav Hajek |
|
Subject: |
[Octave-bug-tracker] [bug #29487] Feature request: svd with 3 output variables should use dgesdd |
|
Date: |
Mon, 03 May 2010 12:24:13 +0000 |
|
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100317 SUSE/3.5.9-0.1.1 Firefox/3.5.9 |
Follow-up Comment #13, bug #29487 (project octave):
Attached is an ill-conditioned matrix that confuses the gesdd driver.
octave:1> load gesdd_bad_matrix.dat
octave:2> [u, s, v] = svd (a);
octave:3> norm (u*s*v' - a, "fro")
ans = 4.2907e-14
octave:4> svd_driver ("gesdd");
octave:5> [u, s, v] = svd (a);
octave:6> norm (u*s*v' - a, "fro")
ans = 70.878
So yes, it should be used more carefully. Given that SVD is used with
ill-conditioned matrices quite often, it's reasonable to stay with gesvd as
the default.
(file #20403)
_______________________________________________________
Additional Item Attachment:
File name: gesdd_bad_matrix.dat Size:128 KB
_______________________________________________________
Reply to this item at:
<http://savannah.gnu.org/bugs/?29487>
_______________________________________________
Message sent via/by Savannah
http://savannah.gnu.org/