Introduction

This book collects notes and examples of scheduling models built with OR-Tools CP-SAT. The focus is on job-shop style problems: sequencing tasks on machines, handling changeovers, respecting breaks and shifts, modeling resources, and grouping tasks into campaigns.

The book is split into two parts.

• Concepts walks through the core modeling ideas once. Read these first if CP-SAT or constraint programming is new to you.
• Examples indexes the Python files in the scheduling/ folder and links each one back to the concepts it demonstrates. Examples are numbered and build on each other, so reading them in order is usually easiest.

All code lives in the scheduling/ directory of the repo. Open a file in your editor while reading the corresponding chapter to see the full model.

A minimal CP-SAT template

Almost every example follows the same five-step shape.

from ortools.sat.python import cp_model

# 1. Data
# ... sets, durations, changeover table, etc.

# 2. Decision variables
model = cp_model.CpModel()
# ... start/end/interval/bool vars

# 3. Objective
make_span = model.new_int_var(0, max_time, "make_span")
model.add_max_equality(make_span, [ends[t] for t in tasks])
model.minimize(make_span)

# 4. Constraints
# ... precedence, resources, circuits, ...

# 5. Solve and post-process
solver = cp_model.CpSolver()
status = solver.solve(model)

The rest of the book explains what goes into step 4.