HiGHS example

from optiwindnet.importer import load_repository
from optiwindnet.svg import svgplot
from optiwindnet.mesh import make_planar_embedding
from optiwindnet.interarraylib import G_from_S
from optiwindnet.heuristics import EW_presolver
from optiwindnet.MILP import solver_factory, ModelOptions

Initialize Triton

locations = load_repository()

L = locations.triton
capacity = 8

svgplot(L)

Optimize Triton

P, A = make_planar_embedding(L)

Initial heuristic solution to warm-start the solver:

Sʹ = EW_presolver(A, capacity=capacity)
Gʹ = G_from_S(Sʹ, A)
svgplot(Gʹ)

solver = solver_factory('highs')

solver.set_problem(
    P, A,
    capacity=Sʹ.graph['capacity'],
    model_options=ModelOptions(
        topology="branched",
        feeder_route="segmented",
        feeder_limit="unlimited",
    ),
    warmstart=Sʹ,
)

solver.solve(
    mip_gap=0.005,
    time_limit=60,
    verbose=True,
)

Running HiGHS 1.11.0 (git hash: n/a): Copyright (c) 2025 HiGHS under MIT licence terms
RUN!
MIP  has 2618 rows; 1764 cols; 9660 nonzeros; 1764 integer variables (882 binary)
Coefficient ranges:
  Matrix [1e+00, 8e+00]
  Cost   [8e+02, 1e+04]
  Bound  [1e+00, 8e+00]
  RHS    [1e+00, 9e+01]
Assessing feasibility of MIP using primal feasibility and integrality tolerance of       1e-06
Solution has               num          max          sum
Col     infeasibilities      0            0            0
Integer infeasibilities      0            0            0
Row     infeasibilities      0            0            0
Row     residuals            0            0            0
Presolving model
2618 rows, 1764 cols, 9660 nonzeros  0s
2320 rows, 1722 cols, 8634 nonzeros  0s

MIP start solution is feasible, objective value is 113076.197044

Solving MIP model with:
   2320 rows
   1722 cols (842 binary, 880 integer, 0 implied int., 0 continuous, 0 domain fixed)
   8634 nonzeros

Src: B => Branching; C => Central rounding; F => Feasibility pump; J => Feasibility jump;
     H => Heuristic; L => Sub-MIP; P => Empty MIP; R => Randomized rounding; Z => ZI Round;
     I => Shifting; S => Solve LP; T => Evaluate node; U => Unbounded; X => User solution;
     z => Trivial zero; l => Trivial lower; u => Trivial upper; p => Trivial point

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work
Src  Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

         0       0         0   0.00%   -21710.457804   113076.197044    119.20%        0      0      0         0     0.1s
         0       0         0   0.00%   103058.96252    113076.197044      8.86%        0      0      3      1337     0.2s
 L       0       0         0   0.00%   104464.184489   108377.625532      3.61%     1159     68    110      3028     2.5s

7.5% inactive integer columns, restarting
Model after restart has 2189 rows, 1591 cols (775 bin., 816 int., 0 impl., 0 cont., 0 dom.fix.), and 8087 nonzeros

         0       0         0   0.00%   104464.185655   108377.625532      3.61%       45      0      0     11293     7.0s
         0       0         0   0.00%   104464.185655   108377.625532      3.61%       45     44      1     11755     7.0s
         0       0         0   0.00%   104464.185655   108377.625532      3.61%       45     44     82     22212    12.8s
        16      13         0   1.17%   104581.335462   108377.625532      3.50%       63     46    239     81564    21.2s
        39      32         0   1.19%   104581.335462   108377.625532      3.50%      220     51    851    120401    26.5s
       145      80        19   1.54%   104581.335462   108377.625532      3.50%     2308     83   4160    149709    33.7s
 L     161      93        19   1.58%   104627.611389   108301.102486      3.39%     2240     88   4334    152193    35.7s
 L     275     115        35   3.75%   104636.344814   107622.069286      2.77%      918     81   6037    169707    39.8s
       428     199        53   4.90%   104651.947562   107622.069286      2.76%      860     85  10070    196590    44.8s
       605     297        75   6.59%   104733.8315     107622.069286      2.68%      945     80   9565    222478    50.0s
       774     403        87   8.40%   104812.054462   107622.069286      2.61%      544     68   9898    248602    55.1s
       956     479       124   8.51%   104848.88925    107622.069286      2.58%      792     90   9879    274146    60.0s

Solving report
  Status            Time limit reached
  Primal bound      107622.069286
  Dual bound        104848.88925
  Gap               2.58% (tolerance: 0.5%)
  P-D integral      2.09509593034
  Solution status   feasible
                    107622.069286 (objective)
                    0 (bound viol.)
                    0 (int. viol.)
                    0 (row viol.)
  Timing            60.00 (total)
                    0.00 (presolve)
                    0.00 (solve)
                    0.00 (postsolve)
  Max sub-MIP depth 5
  Nodes             956
  Repair LPs        0 (0 feasible; 0 iterations)
  LP iterations     274146 (total)
                    144307 (strong br.)
                    11085 (separation)
                    28964 (heuristics)
WARNING: Loading a feasible but suboptimal solution. Please set
load_solution=False and check results.termination_condition and
results.found_feasible_solution() before loading a solution.

SolutionInfo(runtime=<pyomo.opt.results.container.UndefinedData object at 0x000001CA1B986ED0>, bound=104848.88924958107, objective=107622.0692857606, relgap=0.02576776356916277, termination='maxTimeLimit')

S, G = solver.get_solution()

svgplot(G)