bugGNU Octave - Bugs: bug #39903, Error solving linear systems in...

 
 

bug #39903: Error solving linear systems in single precision

Submitted by:  Nir Krakauer <nir_krakauer>
Submitted on:  Fri 30 Aug 2013 02:42:22 PM UTC  
 
Category: LibrariesSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: Works For MeAssigned to: None
Originator Name: Nir KrakauerOpen/Closed: Closed
Release: 3.6.2Operating System: GNU/Linux

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Wed 04 Sep 2013 01:42:20 AM UTC, comment #7:

Good that you are seeing it work with the newer version. Closing since this seems dependent on the libraries and not something that Octave is doing.

Mike Miller <mtmiller>
Project Administrator
Tue 03 Sep 2013 02:54:06 PM UTC, comment #6:

It does work with no problems in my Jessie (unstable) chroot. Guess I'll use that for now.

Nir Krakauer <nir_krakauer>
Mon 02 Sep 2013 10:18:08 PM UTC, comment #5:

Ok, I can confirm the errors when I set up a Debian wheezy chroot. I can still solve all of the attached demo files on a Debian testing system, however, both Octave 3.6.2 and the current development version.

This looks like it may a library problem that has already been fixed in a newer version.

Mike Miller <mtmiller>
Project Administrator
Mon 02 Sep 2013 09:00:26 PM UTC, comment #4:

> Have you tried these test cases with ATLAS removed completely, or by configuring both BLAS and LAPACK to use the netlib versions?


I haven't tried removing ATLAS completely, but changing both BLAS and LAPACK to use the netlib versions resulted in both demo and demo2 working, but another case, attached as demo3, gives the same error. When using ATLAS, demo and demo3 work, but demo2 returns an error.

> Also is your wheezy i386 or amd64?


it's amd64

(file #28981)

Nir Krakauer <nir_krakauer>
Mon 02 Sep 2013 05:48:49 PM UTC, comment #3:

I do not get any failures with either netlib (non-ATLAS) or with ATLAS version 3.10.1 in Debian jessie. I tried both of your attached files.

Have you tried these test cases with ATLAS removed completely, or by configuring both BLAS and LAPACK to use the netlib versions?

Also is your wheezy i386 or amd64?

Mike Miller <mtmiller>
Project Administrator
Mon 02 Sep 2013 02:48:10 PM UTC, comment #2:

I'm using Debian Wheezy (stable) with Octave 3.6.2.

Checking the active BLAS and LAPACK implementations (following https://wiki.debian.org/DebianScience/LinearAlgebraLibraries ) showed that BLAS was the Atlas version while LAPACK was the default (non-Atlas) version. Switching LAPACK also to the Atlas version resulted in no error for the original inputs I gave, but the same error persisted for other sets of inputs, such as those given in the attached demo2.mat

(file #28977)

Nir Krakauer <nir_krakauer>
Sat 31 Aug 2013 04:00:18 AM UTC, comment #1:

Cannot reproduce here, Debian GNU/Linux jessie. Tried with Octave 3.6.2 and with current development version, with both netlib blas/lapack and atlas. What versions of atlas, blas, lapack, or openblas are you using to get this error?

Mike Miller <mtmiller>
Project Administrator
Fri 30 Aug 2013 02:42:22 PM UTC, original submission:

I've been getting sporadic errors of this sort. With the attached example data:

load demo.mat %contains single-precision arrays a and b
c = a \ b;

    • On entry to SLASD4 parameter number -1 had an illegal value

error: exception encountered in Fortran subroutine sgelsd_

However, either of the following does work without problem:

c = pinv(a) * b;

c = double(a) \ double(b);

Nir Krakauer <nir_krakauer>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach File(s):
   
   
Comment:
   

Attached Files
file #28981:  demo3.mat added by nir_krakauer (179KiB - application/octet-stream)
file #28977:  demo2.mat added by nir_krakauer (205KiB - application/octet-stream)
file #28960:  demo.mat added by nir_krakauer (119KiB - application/octet-stream)

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -unavailable- added by mtmiller (Posted a comment)
  • -unavailable- added by nir_krakauer (Submitted the item)
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    Follow 6 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed 04 Sep 2013 01:42:20 AM UTCmtmillerOpen/ClosedOpen=>Closed
    Mon 02 Sep 2013 09:00:26 PM UTCnir_krakauerAttached File-=>Added demo3.mat, #28981
    Mon 02 Sep 2013 02:48:10 PM UTCnir_krakauerAttached File-=>Added demo2.mat, #28977
    Sat 31 Aug 2013 04:00:18 AM UTCmtmillerCategoryNone=>Libraries
      StatusNone=>Works For Me
    Fri 30 Aug 2013 02:42:22 PM UTCnir_krakauerAttached File-=>Added demo.mat, #28960

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