Where discrete rate simulation started
A filling line moving product at high speed is a flow, not a queue of separate parts. Andrew Siprelle created discrete rate simulation in 1990 as “bulk flow” simulation, built to model that flow directly. Models of packaging, food and bulk-handling lines ran far faster than item-by-item models, and the same idea now appears in every major simulation package. The first paper on the method, with David Parsons at the Winter Simulation Conference in 1995, was built using Extend. The full history, with sources, is on the discrete rate lineage page.
The libraries we wrote for Extend
Andy Siprelle adopted Extend, now ExtendSim, before it even had a discrete event library, and worked closely with Bob Diamond, who founded Imagine That and created Extend. Simulation Dynamics went on to write many of the libraries Extend modelers built on:
- SDI Industry and Bulk Flow (Rate): the first commercial discrete rate library, for continuous and high-speed operations.
- SDI Database (SDI DB): models driven by tables instead of hand-set parameters.
- Supply Chain Builder: network-scale blocks. The first VINLogic vehicle distribution model was built with it (read the case).
The Bulk Flow (Rate) and Database libraries sold more than 700 licenses and were the origin of ExtendSim’s Discrete Rate and Database libraries. Andy also created the first official ExtendSim training program, and SDI has since trained thousands of simulation professionals.
Built in ExtendSim, rebuilt in ReliaSim
ReliaSim is the third generation of the method, rebuilt from scratch by the same team. These SDI case studies were first built in ExtendSim (or in SDI’s Supply Chain Builder for ExtendSim) and have since been rebuilt in ReliaSim:
- Soap plant consolidation: the model catches a $4 million quality problem first.
- Olive plant capacity study: 15% more output from scheduling, before buying equipment.
- Brewery expansion: the tanks, not the new lines, set the limit.
- Chemical bag lines vs overtime and a cereal plant that runs its model before every shift.
- Pack at the plant or the DC and sizing capacity before the peak is known.
The rebuild is checked against outside work too. A food plant model that Fischel and Lange published at the 2020 Winter Simulation Conference, originally built in ExtendSim, was rebuilt in ReliaSim and independently validated by Tom Lange. It came within 1% of the plant’s measured OEE and ran about 1,200× faster on the same laptop (the comparison, the case study).
Who we are today
ReliaSim is made by ChiAha in Maryville, Tennessee. Consulting, custom models and ExtendSim work continue at Simulation Dynamics. Customers have always come to us with the hardest line problems, the ones their own teams couldn’t untangle, and they come back because we get to the right answer fast.
ExtendSim® is a registered trademark of Andritz Inc. It is referenced here for identification and historical purposes only; no affiliation or endorsement is implied.