Abstract
Solving the ultimate pit problem remains an important and relevant task in open pit mine planning as a subroutine in sophisticated decision processes, parametric analysis, quantifying the impact of geologic uncertainty, approaching more complicated problems such as production scheduling, or as a subproblem in decomposition. Ultimate pit models often contain dozens of millions of blocks and hundreds of millions of precedence constraints, and they may need to be solved hundreds or even thousands of times. These requirements can quickly overwhelm existing ultimate pit solvers. This paper introduces MineFlow: an open-source C++ library providing efficient and flexible precedence schemes and a stripped down pseudoflow-based solver. In a computational comparison with five modern commercial packages, we show that MineFlow computes consistently identical results in a fraction of the time; for example, with MineFlow a block model containing 16 million blocks is processed in nine seconds, whereas the fastest commercial alternative takes two and a half minutes. These improvements are realized by using implicit precedence schemes and by modifying slightly the conventional pseudoflow algorithm. Additionally, we present a compact notation for the pseudoflow algorithm to assist educators in presenting the latest in ultimate pit optimization.
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Availability of Data and Materials
One of the datasets used during the study is not available due to confidentiality issues. The remaining data are available from the corresponding author.
Code Availability
All code used to generate precedence graphs and compute ultimate pits is available from the corresponding author and at the following link: https://github.com/MineFlowCSM/MineFlow
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Acknowledgments
We thank Dr Marcelo Godoy for sponsoring this project. We also thank Dr Conor Meagher and Dr Ryan Goodfellow, also from Newmont, for useful discussions. Additionally, we thank Lee Jornet Zamalloa Llerena, Graduate Student from the Mining Department at Colorado School of Mines, for assisting us in data conversion and running the commercial packages with the different datasets.
Funding
This work was funded by Newmont Corporation.
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Deutsch, M., Dağdelen, K. & Johnson, T. An Open-Source Program for Efficiently Computing Ultimate Pit Limits: MineFlow. Nat Resour Res 31, 1175–1187 (2022). https://doi.org/10.1007/s11053-022-10035-w
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DOI: https://doi.org/10.1007/s11053-022-10035-w