Re: [ublas] boost numeric bindings lapack gesv + RHEL5 issue.

Subject: Re: [ublas] boost numeric bindings lapack gesv + RHEL5 issue.
From: Sunil Thomas (sgthomas27_at_[hidden])
Date: 2011-09-21 11:52:26

Thanks Rutger!

    On Windows I am using Lapack built with IFC, while on Linux, we are
using already
existing Lapack libraries (built with fortran compilers g77, I think).. The
problem is more
subtle than I thought.. when I build and run my standalong application on
Windows and
Linux, it actually runs fine on both. Its only when I am linking my
application as 3rd party
libraries to a client application, that it fails on Linux. I forgot to
mention this fact and for
that, I apologise. Somehow I think the issue is related to the condition
number of the
matrix. Here it is the matrix (9x9) and RHS:

Matrix:

Row #0
0.1  4.54773e-010  8.62559e-018  0  0  0  0  0  0
Row #1
0  0  0  0.1  4.54773e-010  8.62559e-018  0  0  0
Row #2
0  0  0  0  0  0  0.1  4.54773e-010  8.62559e-018
Row #3
1.44948e-010  0.166667  -2.61688e-018  0  0  0  0  0  0
Row #4
0  0  0  1.44948e-010  0.166667  -2.61688e-018  0  0  0
Row #5
0  0  0  0  0  0  1.44948e-010  0.166667  -2.61688e-018
Row #6
-8.12841e-010  -8.11836e-010  0.0952381  0  0  0  0  0  0
Row #7
0  0  0  -8.12841e-010  -8.11836e-010  0.0952381  0  0  0
Row #8
0  0  0  0  0  0  -8.12841e-010  -8.11836e-010  0.0952381
RHS:
0.1   4.54773e-009   8.62559e-016   1.44948e-010   1.66667   -2.61688e-016
-8.12841e-010   -8.11836e-009   9.52381

This is just a typical example.. since the matrix/RHS changes
from iteration to iteration, say. But since all solves fail (when
they fail on Linux linking to client application), understanding
this problem should suffice, I think.

Thanks again,
--Thomas.

On Tue, Sep 20, 2011 at 11:40 PM, Rutger ter Borg <rutger_at_[hidden]>wrote:

> On 09/20/2011 11:04 PM, Sunil Thomas wrote:
>
>> Hi!
>>   I am using boost numeric bindings for doing a direct solve using the
>> lapack function gesv. While this
>> works great on Windows and gives me the right answer, the exact same
>> matrix (I printed it out to make
>> sure) fails on Linux RHEL4 or RHEL5 (returns info=3, zero element on
>> diagonal). I think the Windows
>> case was able to pivot it automatically. I am working with some legacy
>> code here and I see some lines
>> such as:
>>
>>
> [snip]
>
>
> ()
>>    It looks like the fix might be something really trivial, but I have
>> no clue where to look for a hint to resolve
>> the problem.. appreciate if somebody who's an expert at using boost
>> ublas can kindly help resolve this
>> problem.
>> Thanks a lot for your time,
>> --S.
>>
>
> In order to help, we need a bit more info on your build environments.
> I.e., which LAPACK backends are you using, on Windows and on RHEL? Which
> compilers?
>
> Cheers,
>
> Rutger
>
>
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> Sent to: sgthomas27_at_[hidden]
>