[Cbc] mipstart

[John Forrest]

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
On 17/02/15 11:27, Yves Touchard wrote:
> Hello,
>
> Just a simple question (surely stupid...).
> The solver generates an integer solution file from a very basic 
> constraint file.
> Then I re-compile the same constraint file with the previous solution 
> file as mipsart argument. And cbc claims:
>
> [...]
> /will open mipstart file ./bug_gen.sol.//
> //mipstart values read for 3 variables.//
> [...]
> //Cbc0045I Warning: mipstart values could not be used to build a solution.
> Cbc0045I Trying just fixing integer variables.
> Cbc0045I mipstart provided solution with cost 127.464
> [..]
>
> /What does mean the warning?
> Is there something i miss.
>
> Thanks
>
> Yves
>
>
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