[Coin-discuss] Warmstart/basis reuse

[Esben Mose Hansen]

On Wednesday July 18 2007 17:44:03 John J Forrest wrote:
> Esben,
>
> Presolve tries to update basis as it reduces the size of the problem but
> it does have a much better chance of doing this correctly with the column
> solution as you suggest.  If you start with a basis of full rank then
> every time a row is removed something has to leave basis - but where to?
> If the solution value is 7.0 and the removed row puts an upper bound of
> 7.0 on the variable then it is a good guess to put the variable at its
> upper bound.  Without solution values the code has no idea which bound to
> put it to.

Is this what cbc does with BasisIn and BasisOut? Because my collegue made a 
test using these methods and a bunch of similar problems, and there it worked 
well. As far as I can see, BasisOut stores the basis variable, the 
correspoding row, and the column solution in that row. It also have some 
flags (XL/XU) which I havn't divined the meaning of yet.

Thanks for helping :D

-- 
regards, Esben