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@terborg.net> 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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