pybnb 0.6.1

快速启动

定义问题：

# simple.pyimportpybnbclassSimple(pybnb.Problem):def__init__(self):self.bounds=[0.0,1.0]defsense(self):returnpybnb.minimizedefobjective(self):returnround(self.bounds[1]-self.bounds[0],3)defbound(self):return-(self.bounds[1]-self.bounds[0])**2defsave_state(self,node):node.state=self.boundsdefload_state(self,node):self.bounds=node.statedefbranch(self):L,U=self.boundsmid=0.5*(L+U)forl,uin[(L,mid),(mid,U)]:child=pybnb.Node()child.state=(l,u)yieldchild

编写求解脚本：

# solve_simple.pyimportsimpleproblem=simple.Simple()results=pybnb.solve(problem,absolute_gap=1e-9)

运行脚本：

$ mpirun -np 4 python solve_simple.py

Using non-default solver options:
 - absolute_gap: 1e-09 (default: 0)

Starting branch & bound solve:
 - dispatcher pid: 34902(Ozymandias.local)
 - worker processes: 3
---------------------------------------------------------------------------------------------------------------------------
         Nodes        |                      Objective Bounds                        |              Work
      Expl    Unexpl  |      Incumbent           Bound     Rel. Gap         Abs. Gap | Time (s)  Nodes/Sec Imbalance   Idle
         01|            inf            -inf          inf%             inf |0.0       0.00     0.00%      0
*        12|1              -1  200.0000000%               2|0.0    1226.99   300.00%      1
*        23|0.5              -1  150.0000000%             1.5 |0.0    2966.04   150.00%      0
*        45|0.25           -0.25   50.0000000%             0.5 |0.0    8081.95    75.00%      0
*        89|0.125         -0.0625   18.7500000%          0.1875 |0.0   12566.90    37.50%      0
      Expl    Unexpl  |      Incumbent           Bound     Rel. Gap         Abs. Gap | Time (s)  Nodes/Sec Imbalance   Idle
*       1617|0.062       -0.015625    7.7625000%        0.077625 |0.0   15352.74    18.75%      0
*       3233|0.031     -0.00390625    3.4906250%      0.03490625 |0.0   15981.49    18.75%      0
*       6465|0.016   -0.0009765625    1.6976563%    0.0169765625 |0.0   18740.68    18.75%      0
*      128129|0.008   -0.0002441406    0.8244141%  0.008244140625 |0.0   21573.51    11.72%      0
*      256257|0.004   -6.103516e-05    0.4061035%  0.004061035156 |0.0   22166.96     8.20%      0
      Expl    Unexpl  |      Incumbent           Bound     Rel. Gap         Abs. Gap | Time (s)  Nodes/Sec Imbalance   Idle
*      512513|0.002   -1.525879e-05    0.2015259%  0.002015258789 |0.0   21177.00     5.86%      0
*     10241025|0.001   -3.814697e-06    0.1003815%  0.001003814697 |0.1   19978.42     9.38%      0
*     20482049|0   -9.536743e-07    0.0000954% 9.536743164e-07 |0.1   21606.45     5.42%      02402924030|0   -1.490116e-08    0.0000015% 1.490116119e-08 |1.1   21961.03     5.98%      04615946160|0    -3.72529e-09    0.0000004% 3.725290298e-09 |2.1   22120.75     5.73%      0
      Expl    Unexpl  |      Incumbent           Bound     Rel. Gap         Abs. Gap | Time (s)  Nodes/Sec Imbalance   Idle
     6553765538|0   -9.313226e-10    0.0000001% 9.313225746e-10 |3.0   22459.50     6.20%      0
---------------------------------------------------------------------------------------------------------------------------

Absolute optimality tolerance met
Optimal solution found!

solver results:
 - solution_status: optimal
 - termination_condition: optimality
 - objective: 0
 - bound: -9.313226e-10
 - absolute_gap: 9.313226e-10
 - relative_gap: 9.313226e-10
 - nodes: 65537
 - wall_time: 2.96 s
 - best_node: Node(objective=0)

Number of Workers:        3
Load Imbalance:       6.20%
 - min: 21355(proc rank=3)
 - max: 22710(proc rank=1)
Average Worker Timing:
 - queue:      80.78% [avg time: 109.6 us, count: 65537]
 - load_state:  0.44% [avg time: 596.1 ns, count: 65537]
 - bound:       0.59% [avg time: 796.1 ns, count: 65537]
 - objective:   3.52% [avg time:   4.7 us, count: 65537]
 - branch:      3.36% [avg time:   4.6 us, count: 65537]
 - other:      11.31% [avg time:  15.3 us, count: 65537]