I have an binary model (all variables are binary)
For one particular instance, the LP relaxation generates a binary
solution. I checked this with the --nomip option and verified the
solution is completely binary.
The LP relaxation is solved first inside the MIP solver.
However, the branch and cut part of the MIP solver gets called and the
callback function gets called with the reason CUTGEN.
I list next the logfile of this run. Note that solution values of LP
relaxation and MIP are identical.
0: obj = 1.009800000e+004 infeas = 1.800e+003 (0)
500: obj = 1.049500000e+004 infeas = 1.800e+002 (0)
* 988: obj = 1.063500000e+004 infeas = 0.000e+000 (0)
* 1000: obj = 1.054200000e+004 infeas = 0.000e+000 (0)
* 1500: obj = 8.642500000e+003 infeas = 3.151e-014 (0)
* 2000: obj = 5.304500000e+003 infeas = 1.226e-016 (0)
* 2500: obj = 3.092666667e+003 infeas = 4.914e-016 (0)
* 3000: obj = 1.524000000e+003 infeas = 2.498e-015 (0)
* 3385: obj = 1.041000000e+003 infeas = 0.000e+000 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+ 3385: mip = not found yet >= -inf (1; 0)
+ 3401: >>>>> 1.041000000e+003 >= 1.041000000e+003 0.0% (2; 0)
+ 3401: mip = 1.041000000e+003 >= tree is empty 0.0% (0; 3)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 1.6 secs
Memory used: 10.4 Mb (10947806 bytes)
Why is the branch and cut section of the MIP solver even called.
How can the unnecessary call to the cut generation routine be avoided?
--
Marc Goetschalckx
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