Benchmark Instances for Manual Warehouse Order Picking

Repository Structure

Top-level folders:

Data_input/ – Static input data (warehouse layouts and storage assignments)
Orders/ – Order streams (instances) for different experimental settings
Results/ – Example/benchmark solutions for selected instances (for validation)

Within Data_input/ and Orders/, data is split into two experimental designs:

OFAT/ – One-Factor-at-a-Time design
LHS/ – Latin Hypercube Sampling design

Orders/OFAT/Standard_case/ contains the baseline setting.
Each other folder under Orders/OFAT/ changes exactly one factor relative to the standard case.
Orders/LHS/ contains 100 parameter sets (Latin Hypercube Sampling), each with 100 replications.

Warehouse Layouts
Geometric and Logical Structure

The warehouse is modeled as a rectangular layout with:

Parallel picking aisles
One cross aisle at the bottom and one at the top
A depot at coordinate (0, 0) (in abstract length units)

Layouts are represented as NetworkX graphs stored as pickle files (*.pkl) in Data_input/.../Layout/.

Storage assignments are stored as JSON files in Data_input/.../Storage_assignment/.

Each file in Orders/ is a JSON file representing one replication (= one shift/day) for a given parameter setting.

Top-level structure:

meta: metadata and configuration of the instance
orders: list of orders for this instance

OFAT Design (One-Factor-at-a-Time)

The OFAT design is organized in subfolders under Orders/OFAT/.
Each folder modifies exactly one factor relative to the Standard_case/.

Each OFAT subfolder contains:

A set of factor levels (e.g. multiple due date settings, layout variants, etc.).
For each factor level: 100 JSON instances (replications), each representing one shift.

LHS Design (Latin Hypercube Sampling)

The LHS design jointly varies multiple parameters instead of changing one factor at a time.

Location: Orders/LHS/

Contains 100 different parameter sets (Latin Hypercube samples).
For each parameter set: 100 replications (instances).

Results

The Results/ folder contains example/benchmark solutions for selected instances, separated into OFAT and LHS.

Abbreviations:
OFAT: One factor at a time
LHS: Latin Hypercube Sampling
MOCT: Mean order completion time
MLPI: Mean length per item
TARD: Tardiness
SSH: S-Shape Routing
NNH: Nearest Neighbourhood Routing
LAG: Largest Gap Routing
RET: Return Routing
W: Waiting for full batches
WOC_x: Waiting Order Count (Waiting for x orders in batch before starting)
SI: Start Immediately (no waiting)

Please refer to the attached readme file for more details regarding implementation and data description.