I guess this is because I solve a MIP problem, so I need some variables to be integers in the end. So I call: osi->initialSolve(); and then: osi->branchAndBound(); I guess the branch and bound part implies some Cbc call... -- Christophe-Marie Duquesne 06 84 14 26 82 - mobile 04 76 57 48 06 - g-scop 04 97 23 27 33 - amadeus