Dual bound not moving
Answered
Hi
I'm trying to solve a MIP problem with Gurobi and C++, but the process doesn't seem to go anywhere.
It looks like it's going to start on the branch and bound tree, but for about 3000 seconds almost nothing happens. The dual bound just moves slightly. Should I change some parameter?
Thanks!
Optimize a model with 1323 rows, 3252804 columns and 63914302 nonzeros
Variable types: 144 continuous, 3252660 integer (3252660 binary)
Coefficient statistics:
Matrix range [1e+00, 9e+02]
Objective range [3e+03, 2e+04]
Bounds range [1e+00, 6e+02]
RHS range [1e+00, 7e+02]
Presolve removed 0 rows and 0 columns (presolve time = 5s) ...
Presolve removed 370 rows and 310 columns (presolve time = 11s) ...
Presolve removed 370 rows and 310 columns (presolve time = 21s) ...
Presolve removed 370 rows and 310 columns (presolve time = 25s) ...
Presolve removed 370 rows and 310 columns (presolve time = 30s) ...
Presolve removed 370 rows and 310 columns (presolve time = 38s) ...
Presolve removed 370 rows and 310 columns (presolve time = 40s) ...
Presolve removed 370 rows and 310 columns (presolve time = 45s) ...
Presolve removed 430 rows and 370 columns (presolve time = 68s) ...
Presolve removed 430 rows and 638 columns (presolve time = 94s) ...
Presolve removed 370 rows and 578 columns
Presolve time: 94.28s
Presolved: 953 rows, 3252226 columns, 56358962 nonzeros
Variable types: 144 continuous, 3252082 integer (3252082 binary)
Root simplex log...
Iteration Objective Primal Inf. Dual Inf. Time
0 0.0000000e+00 8.480000e+02 0.000000e+00 190s
Starting sifting (using dual simplex for sub-problems)...
Iter Pivots Primal Obj Dual Obj Time
0 0 infinity 0.0000000e+00 190s
1 544 8.4800000e+08 3.1787187e+04 190s
2 821 8.4800000e+08 3.7021568e+04 191s
3 1182 6.5067763e+08 4.0649270e+04 192s
4 1657 4.6936564e+08 4.4552407e+04 192s
5 1999 3.3405031e+08 4.4873758e+04 193s
6 2512 3.0050789e+08 4.5084212e+04 194s
7 2954 1.9741603e+08 4.5299313e+04 194s
8 3470 1.6426142e+08 4.5810106e+04 195s
9 3966 1.1383722e+08 4.5946492e+04 195s
10 4431 1.0543754e+08 4.6017063e+04 196s
11 4917 8.2632950e+07 4.8126427e+04 197s
12 5700 4.0386019e+07 4.8682048e+04 197s
13 6656 3.2108431e+07 5.3515626e+04 198s
14 7565 1.1114809e+05 5.3699998e+04 199s
15 8364 9.8625035e+04 5.7325481e+04 199s
16 9447 8.9931196e+04 6.3742581e+04 200s
17 10356 8.7017449e+04 7.1049922e+04 201s
18 11263 8.6827300e+04 7.4869439e+04 201s
19 12179 8.6470143e+04 7.7239759e+04 202s
20 13049 8.6437305e+04 8.0532984e+04 202s
21 13979 8.6437305e+04 8.2216446e+04 203s
22 14856 8.6437305e+04 8.3302146e+04 204s
Sifting complete
15740 8.6437305e+04 0.000000e+00 0.000000e+00 210s
Root relaxation: objective 8.643730e+04, 15740 iterations, 26.59 seconds
Total elapsed time = 215.14s
Nodes | Current Node | Objective Bounds | Work
Expl Unexpl | Obj Depth IntInf | Incumbent BestBd Gap | It/Node Time
0 0 86437.3048 0 93 - 86437.3048 - - 299s
0 0 86506.5351 0 134 - 86506.5351 - - 624s
0 0 86571.9562 0 147 - 86571.9562 - - 718s
0 0 86571.9562 0 149 - 86571.9562 - - 733s
0 0 86735.0546 0 148 - 86735.0546 - - 963s
0 0 86743.5933 0 150 - 86743.5933 - - 1025s
0 0 86757.5074 0 157 - 86757.5074 - - 1074s
0 0 86757.5074 0 157 - 86757.5074 - - 1086s
0 0 86786.2574 0 157 - 86786.2574 - - 1297s
0 0 86798.7224 0 160 - 86798.7224 - - 1389s
0 0 86798.7224 0 166 - 86798.7224 - - 1397s
0 0 86798.8282 0 178 - 86798.8282 - - 1581s
0 0 86798.8455 0 181 - 86798.8455 - - 1627s
0 0 86807.5651 0 138 - 86807.5651 - - 1828s
0 0 86807.5651 0 138 - 86807.5651 - - 1878s
0 0 86815.4812 0 173 - 86815.4812 - - 1965s
0 0 86815.4812 0 175 - 86815.4812 - - 1978s
0 0 86815.5466 0 174 - 86815.5466 - - 2172s
0 0 86818.4603 0 170 - 86818.4603 - - 2232s
0 0 86821.0201 0 180 - 86821.0201 - - 2261s
0 0 86822.4161 0 169 - 86822.4161 - - 2279s
0 0 86822.4161 0 169 - 86822.4161 - - 2296s
0 0 86844.6999 0 139 - 86844.6999 - - 2475s
0 0 86844.6999 0 149 - 86844.6999 - - 2526s
0 0 86844.6999 0 147 - 86844.6999 - - 2701s
0 0 86844.6999 0 147 - 86844.6999 - - 2744s
0 0 86844.6999 0 125 - 86844.6999 - - 2924s
0 0 86844.6999 0 143 - 86844.6999 - - 2977s
0 0 86844.6999 0 141 - 86844.6999 - - 3147s
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Hi!
You could try to limit the number of cuts that are generated in the root node since they seem to cost a lot of time. You could try to use MIPFocus=1 to hopefully find feasible solutions earlier.
I hope this helps. Please also note that you are dealing with a lot of binary variables and hence the problem might just be quite hard.
Best regards,
Matthias0 -
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