The global optimiser works-What next?

Abstract

The Global Optimiser used by Whittle Consulting has gone through three major versions to date. The first was based on the Milawa optimisation algorithm; it worked, but had many shortcomings. The second, known internally as ProberA, had a different approach to optimisation in that it used a series of random starting points and found the nearest local NPV maximum to each. It did this a sufficient number of times to give us some confidence that the best result found was close to optimal. ProberB was an enhanced version of ProberA, with the ability to handle a wider range of constraints, particularly with regard to limits on the dif- ferences in depth between adjacent areas of a pit. ProberB has been used suc- cessfully for some time now. It has produced excellent Life of Project schedules for a wide range of very large mining complexes. However, like any piece of software, it has its limitations. For example, it only copes directly with three steps-mining, processing, and blending. It is possible to 'fool' the program into handling other steps, but only by using mental and mathematical gymnastics. This paper reviews the mechanisms behind the Prober series and describes the plans for the next version-ProberC.