Re: [eclipse-clp-users] Empty problem

From: Kish Shen <kisshen_at_...5...>
Date: Sun, 07 Feb 2010 23:47:02 +0000
vicenç wrote:
> Dear all,
> 
> sometimes I get the following message:
> 
> 
> Empty problem - 0 rows, 1 columns and 0 elements
> 
> 6 times. It only appears if I run the program in a terminal (no  tkeclipse) and the results I obtain are the same in both cases, so doesn´t look serious, but I'm curious. What can be the reason?
> 
> Thanks in advance,
> 
> 
>   Vicenç
> 
Hi Vicenç,

You have not stated what you are running to get these messages. However, 
it seems likely that you are running eplex, and using the CLP/CBC 
solvers. If this is the case, then these messages are generated by those 
solvers.

In general, external solvers generate a fair amount of messages when 
solving a problem. Normally, these messages are generated via an 
interface that is part of the API to the solver, so that the programmer 
can control how the messages are printed. In eplex's case, most messages 
are suppressed, except for errors and warnings. However, I have noticed 
that for CBC/CLP, some of the messages are printed directly to stdout, 
rather than using their output API, and eplex have no control over such 
messages. In your case, you don't see the messages in tkeclipse because 
they are written directly to the (C-level) stdout stream directly, which 
is not in tkeclipse.

As for the exact meaning of the message, it is saying that the solver 
has been given an empty problem that have no constraints (0 rows) and 1 
variable (1 columns). This is either because your program supplied such 
a problem to be solved, or perhaps because the optimisation (presolve) 
of the problem manage to reduce the probelm toan empty one by 
eliminating all the constraints.

Cheers,

Kish

-- 
This e-mail may contain confidential and privileged material for the
sole use of the intended recipient. Any review, use, distribution or
disclosure by others is strictly prohibited. If you are not the intended
recipient (or authorized to receive for the recipient), please contact
the sender by reply e-mail and delete all copies of this message.
Cisco Systems Limited (Company Number: 02558939), is registered in
England and Wales with its registered office at 1 Callaghan Square,
Cardiff, South Glamorgan CF10 5BT.
Received on Sun Feb 07 2010 - 23:47:23 CET

This archive was generated by hypermail 2.2.0 : Mon Jul 09 2018 - 02:05:29 CEST