[Coin-discuss] (no subject)

[Laszlo Ladanyi]

Hi Vivian,

The behavior you describe is certainly incorrect. Could you run the Osi
unitTest? That should point to where the error is. We can't run it easily 'cos
we don't have easy access to cplex.

The real reason of the problem is cplex's interpretation of sense/rhs/range.
In the MPS standard range can take negative value *only* if the constraint is
'E' (then it's a shift), otherwise range must be non-negative. cplex deviated
from this (their interpretation is logical: 0 and range are the bounds on the
surplus variable), and hence we had some translation to do and apparently
something is messed up. 

xpress and cplex both take sense/rhs/range triplets, but they interpret them
differently. So the Osi interface was certain to disagree with one of them. We
went with the xpress interpretation (that also follows the standard) simply
because we did the xpress interface first. Unfortunately this means that now
if someone wants to convert a code from cplex to Osi then simple function name
replacement will not do in case of ranged rows. 

But, as I said, there must be something wrong to get what you did, and it
ought to be fixed.

--Laci

On Thu, 19 Sep 2002 Vivian.DeSmedt at aisystems.be wrote:

> Dear Osi,
> 
> This mail just to highlight somthing that look like a conflit between
>      the Cplex implementation of the Osi interface and
>      the OsiSolverInterface::convertSenseToBound.
> 
> It seems that for Osi
>      sense = R
>      rhs = 15
>      rngvalue = 10
> 
> means:
>      [5, 15] for Osi
> and
>      [15, 25] for Cplex implementation of Osi.
> 
> It seems that for Osi
>      sense = R
>      rhs = 15
>      rngvalue = -10
> 
> means:
>      [25, 15] for Osi (look a bit strange as interval)
> and
>      [5, 15] for Cplex implementation of Osi.
> 
> Should we fix something?
> And is so in which direction. My opinion as a frequent user of Cplex is to
> go in the direction of changing the convertSenseToBound function but I want
> to listen about the other user before submitting a patch.
> 
> Vivian.
> 
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