hermax 1.2.1

A Python library of incremental MaxSAT solvers

Hermax: MaxSAT Optimization for Python

Hermax is a Python bridge to high-performance MaxSAT backends, with a unified IPAMIR-inspired interface for hard clauses, soft literals, assumptions, and iterative optimization workflows.

Why Hermax

• High-level modeling API (hermax.model) with typed variables, vectors, matrices, intervals, and lazy arithmetic.
• Unified API across heterogeneous MaxSAT engines.
• Incremental and non-incremental solver families
• Scientific and reproducible workflow
• Native compatibility with PySAT

Who Is This For?

Hermax is for combinatorially hard problems where:

• finding even a good base solution is already difficult
• the search state is mostly boolean

This is usually a better fit than MILP tooling when your problem is not mainly about floating-point structure, large integer arithmetic, or strong LP relaxations. In those cases, a MILP such as PuLP, SCIP, or Gurobi is often the more natural first choice.

If your problem is highly combinatorial but can benefit from a broader black-box CP approach, CP-SAT may also be a good alternative.

Hermax is especially relevant for:

• engineers building repeated optimization workflows around hard clauses, soft literals, assumptions, and iterative solve loops,
• users who already work with clauses, WCNF, or incremental solver-style APIs, and
• researchers comparing MaxSAT backends behind a common Python interface.

Installation

Core install:

pip install hermax

• User and API docs: https://hermax.readthedocs.io

Modeling Example

from hermax.model import Model

m = Model()

# Decision variables
x = m.int_vector("x", length=4, lb=0, ub=6)       # integer domain [0, 6]
use_bonus = m.bool("use_bonus")

# Hard constraints
m &= x.all_different()
m &= (x[0] + x[1] <= x[2] + 2)
m &= (x[3] >= 2).only_if(use_bonus)

# Soft objective terms
m.obj[5] += (x[0] == 1)
m.obj[3] += ~use_bonus

r = m.solve()  # auto-routes SAT/MaxSAT based on model content
print(r.status, r.cost)

Incremental MaxSAT Example

from hermax.incremental import UWrMaxSAT

solver = UWrMaxSAT()
solver.add_clause([1, 2])   # hard
solver.set_soft(-1, 10)     # soft weight
solver.set_soft(-1, 6)      # update weight (last-wins)

ok = solver.solve(assumptions=[-2])
print("status:", solver.get_status().name)
if ok:
    print("cost:", solver.get_cost())
    print("model:", solver.get_model())

Citation

Hermax is designed for the incremental MaxSAT setting formalized by:

• Niskanen, Berg, Jarvisalo. Incremental Maximum Satisfiability. SAT 2022.

If you use Hermax in research:

1. Cite the repository: https://github.com/josalhor/hermax
2. Cite the backend solver papers relevant to your experiments (see CITATION.cff as a starting point)
3. See additional attribution and latest-paper list in NOTICE.

License

This repository is licensed under Apache License 2.0. See LICENSE. Third-party integrated solvers may have additional license terms.