[Cbc] Very different results with CBC/CLP 2.7.7

[Hervé BOUVART]

Dear John,

I solve a large problem (470000 rows, 655000 cols), in continuous variables
(now, after numerous attempts with integer variables).
It appears that the solution, also given by other solvers is ok using
version 2.7.7 of CLP, if I provide -preO 12 as an option (infeasible or
unbounded if presolver is used without option).
With version 2.8, I get a solution which is 25% different! Moreover the
-preO options does not seem to help anymore.
My .MPS file is over 134 MB, so I don't attach it here.

What is the meaning of the figure after -preO (presolve options) command?

I use CLP and CBC compiled via MS Visual C++ 2010 Express.

Thanks in advance,

Herve
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