challenges / jobshop-taillard-open
Job shop scheduling, Taillard's open 30x20 instances
Minimise the makespan on Taillard's ten 30-job, 20-machine job shop instances ta41-ta50, the only Taillard group where every best-known schedule is still unproven. The eval rebuilds the schedule from your machine orders and scores best-known / yours.
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# Job shop scheduling, Taillard's open 30x20 instances
## Goal
A **job shop** has `n` jobs and `m` machines. Each job is a fixed sequence of `m` operations, one
per machine, each with an integer duration; a machine processes one operation at a time; no
preemption. The **makespan** is the time the last operation finishes. Minimise it.
Taillard's 1993 benchmark set has 80 instances. Fifty years of tabu search, constraint programming
and hybrids have closed most of them, but the ten **30-job, 20-machine** instances `ta41`-`ta50`
are all still open: for each the best-known schedule is strictly above the best proven lower
bound (by 2 to 94 units). Those ten are the whole benchmark here. Any schedule shorter than a
best-known one is a new upper bound on a problem people have attacked since 1993.
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