The Mixed Integer Linear Programming Solver
Node Log
The following information about the status of the branch-and-bound algorithm is printed in the node log:
- Node
indicates the sequence number of the current node in the search tree.
- Active
indicates the current number of active nodes in the branch-and-bound tree.
- Sols
indicates the number of feasible solutions that are found so far. You can use the MAXPOOLSOLS= option to obtain more than one solution. Note that the number printed in the node log can be different from the number of found solutions that is reported in the solution summary and in the _OROPTMODEL_ macro variable.
- BestInteger
indicates the best upper bound (assuming minimization) that is found so far.
- BestBound
indicates the best lower bound (assuming minimization) that is found so far.
- Gap
indicates the relative gap between BestInteger and BestBound, displayed as a percentage. If the relative gap is larger than 1,000, then the absolute gap is displayed. If no active nodes remain, the value of Gap is 0.
- Time
indicates the elapsed real or CPU time.
The LOGFREQ= option can be used to control the amount of information that is printed in the node log. By default, the root node processing information is printed and, if possible, an entry is made every five seconds. A new entry is also included each time a better integer solution is found. The LOGFREQ= option enables you to change the interval between entries in the node log. Figure 3 shows a sample node log.
Figure 3: Sample Node Log
| NOTE: Problem generation will use 16 threads. |
| NOTE: The problem has 510 variables (0 free, 0 fixed). |
| NOTE: The problem uses 1 implicit variables. |
| NOTE: The problem has 510 binary and 0 integer variables. |
| NOTE: The problem has 560 linear constraints (510 LE, 50 EQ, 0 GE, 0 range). |
| NOTE: The problem has 2010 linear constraint coefficients. |
| NOTE: The problem has 0 nonlinear constraints (0 LE, 0 EQ, 0 GE, 0 range). |
| NOTE: The initial MILP heuristics are applied. |
| NOTE: The MILP presolver value AUTOMATIC is applied. |
| NOTE: The MILP presolver removed 0 variables and 0 constraints. |
| NOTE: The MILP presolver removed 0 constraint coefficients. |
| NOTE: The MILP presolver modified 0 constraint coefficients. |
| NOTE: The presolved problem has 510 variables, 560 constraints, and 2010 |
| constraint coefficients. |
| NOTE: The MILP solver is called. |
| NOTE: The parallel Branch and Cut algorithm is used. |
| NOTE: The Branch and Cut algorithm is using up to 16 threads. |
| Node Active Sols BestInteger BestBound Gap Time |
| 0 1 5 24086.8916716 0 24087 0 |
| 0 1 5 24086.8916716 19197.7909681 25.47% 0 |
| 0 1 5 24086.8916716 19206.4233772 25.41% 0 |
| 0 1 5 24086.8916716 19210.6350488 25.38% 0 |
| 0 1 5 24086.8916716 19215.5729975 25.35% 0 |
| 0 1 5 24086.8916716 19222.4722921 25.31% 0 |
| 0 1 7 21763.2006534 19222.4722921 13.22% 0 |
| 0 1 7 21763.2006534 19226.6966446 13.19% 0 |
| 0 1 7 21763.2006534 19229.2373163 13.18% 0 |
| 0 1 7 21763.2006534 19230.1316195 13.17% 0 |
| 0 1 7 21763.2006534 19232.6824642 13.16% 0 |
| NOTE: The MILP solver added 23 cuts with 928 cut coefficients at the root. |
| 12 9 8 21732.8546805 19249.1200242 12.90% 0 |
| 29 23 9 21727.9429145 19251.5508014 12.86% 0 |
| 74 30 12 21671.2531435 19308.8992583 12.23% 0 |
| 123 28 14 21625.4316216 19811.6833584 9.15% 0 |
| 208 30 16 21576.4642867 20401.2386112 5.76% 1 |
| 212 31 17 21551.1485231 20401.2386112 5.64% 1 |
| 246 44 18 21550.7090288 21536.4949513 0.07% 1 |
| 312 31 19 21549.6785006 21537.1297300 0.06% 1 |
| 326 29 20 21549.6785006 21538.7289442 0.05% 1 |
| 433 24 21 21548.2906446 21543.2919592 0.02% 1 |
| 516 10 22 21548.1764622 21543.2919592 0.02% 3 |
| 537 8 23 21548.1764619 21545.1380498 0.01% 3 |
| 548 1 23 21548.1764619 21547.3600586 0.00% 3 |
| NOTE: Optimal within relative gap. |
| NOTE: Objective = 21548.176462. |