[Osi] OsiClp branchandbound

[Jan-Willem Goossens]

Hi,

I understand that the "branchAndBound" method as part of OsiClpSolverInterface is not for 'heavy' use, however:
Is it correct that OsiClp will only solve problems where the integer variables have reasonable upper (and lower, I guess) bounds?

For example, I've tried a simple problem like   max x1 + x2, st.   x1 + 2 * x2 <= 3.9   with x1, x2 >= 0 and integer.

NAME          BLANK   
ROWS
 N  OBJROW
 L  R0000000
COLUMNS
    C0000000  OBJROW    1.             R0000000  1.          
    C0000001  OBJROW    1.             R0000000  2.          
RHS
    RHS       R0000000  3.9         
BOUNDS
 UI BOUND     C0000000         1e+30
 UI BOUND     C0000001         1e+30
ENDATA

This wont solve correctly  

Coin0506I Presolve 0 (-1) rows, 0 (-2) columns and 0 (-2) elements
Clp0000I Optimal - objective value 3.9
Coin0511I After Postsolve, objective 3.9, infeasibilities - dual 0 (0), primal 0 (0)
Clp0032I Optimal objective 3.9 - 0 iterations time 0.002, Presolve 0.00
Clp0006I 0  Obj 3.9 Primal inf 3.9 (1)
Clp0006I 1  Obj -0
Clp0001I Primal infeasible - objective value -0
(and stops here)

unless I add something like x1, x2 <= 10

Is this an (undocument?) requirement, or am I doing something wrong..

Thanks,

Jan-Willem Goossens



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