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2025

AI Planning / Optimization

Ski Trip Planner Benchmark: Z3 vs Gurobi vs Pure LLM

A rigorous comparison of Z3, Gurobi, and solver-free LLM reasoning on constrained, real-data ski trip planning.

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1,009

ski resorts

15

benchmark queries

87.5%

Z3 constraint score

Python
Z3
Gurobi
LLMs
Constraint Solving

Overview

The benchmark asks a practical question: when a natural-language planning problem contains hard budgets, destinations, equipment, transport, and feasibility constraints, is an LLM alone enough? It compares pure language-model reasoning with two formally grounded planners over real ski-resort and rental data.

Challenge

Planning responses can look convincing while silently violating budgets or omitting required services. The evaluation therefore needed to measure more than fluency: feasibility, hard-constraint satisfaction, commonsense consistency, optimality, repair quality, runtime, and cost all had to be scored.

Outcome

Across fifteen queries and four difficulty bands, the reported results show a clear gap between plausible text and verified plans: Z3 reached 87.5% constraint satisfaction versus 16.7% for the pure LLM baseline, while Gurobi delivered the fastest average runtime in the headline comparison.

Technical approach

From the research question to a working system.

  1. 01

    Parse natural-language requirements into destinations, duration, party size, budget, rentals, and slope preferences.

  2. 02

    Run equivalent planning tasks through pure LLM, Z3 SMT, and Gurobi optimization pipelines.

  3. 03

    Aggregate pass rate, hard and commonsense constraints, optimality, repair success, runtime, and cost metrics.