[Cbc] Cbc Digest, Vol 92, Issue 17

[Yves Touchard]

John,

Thanks again for the speed of your reply.

There are continuous variables in the problem.
But, i build a trivial solution where the value of these variables are always integer (in fact, they should be declared as integer variables but we don't care about the precision of these variables as long as their values are bounded - and in my mind, the less the problem have integer variables, the better it is for the solver).

So, if i have well understood your reply, i can try to set these variables with an integer value (no problem of accuracy).

Yves

Le 02/17/2015 06:00 PM, cbc-request at list.coin-or.org<mailto:cbc-request at list.coin-or.org> a écrit :

Message: 4
Date: Tue, 17 Feb 2015 12:18:32 +0000
From: John Forrest <john.forrest at fastercoin.com><mailto:john.forrest at fastercoin.com>
To: cbc at list.coin-or.org<mailto:cbc at list.coin-or.org>
Subject: Re: [Cbc] mipstart
Message-ID: <54E33198.7000307 at fastercoin.com><mailto:54E33198.7000307 at fastercoin.com>
Content-Type: text/plain; charset="windows-1252"; Format="flowed"

Yves,

If there are no continuous variables - this is a bug.

Assuming there are -

The idea is to use the solution from one problem for a different
problem.  Initially the code fixes the continuous variables as well as
integer variables to try and keep as much information as possible.
Looking at the code, I see that if a variable is not mentioned then it
will be fixed to zero!  This means that the solution with all variables
fixed will very likely be infeasible. Even if all variables are in file
then it is still possible that, due to printing inaccuracy and/or
different bases giving slightly different values for continuous
variables, it is possible for the problem with all variables fixed to be
slightly infeasible.  If this happens you get those messages.

At least I should change code to set unmentioned variables to bound
nearest zero.  It might be better to set the values to infinity to
indicate not set and then be more sensible when the new solution is
generated.

John


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