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

 
 

bug #39903: Error solving linear systems in single precision

Submitter:  Nir Krakauer <nir_krakauer>
Submitted:  Fri 30 Aug 2013 02:42:22 PM UTC
   
 
Category:  Libraries Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Works For Me Assigned to:  None
Originator Name:  Nir Krakauer Open/Closed:  * Closed
Release:  * 3.6.2 Operating System:  * GNU/Linux
Fixed Release:  None Planned Release:  None
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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>
Group Member
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>
Group Member
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>
Group Member
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>
Group Member
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>

 

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Attach Files:
   
   
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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

 

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    Follow 6 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2013-09-04 mtmiller Open/ClosedOpen Closed
    2013-09-02 nir_krakauer Attached File- Added demo3.mat, #28981
    2013-09-02 nir_krakauer Attached File- Added demo2.mat, #28977
    2013-08-31 mtmiller CategoryNone Libraries
        StatusNone Works For Me
    2013-08-30 nir_krakauer Attached File- Added demo.mat, #28960

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