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Potential bug in Gurobi 8.0.0 #78

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jeffreyhanson opened this Issue Apr 27, 2018 · 2 comments

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jeffreyhanson commented Apr 27, 2018

I think I've found a potential bug in Gurobi 8.0.0, wherein a problem with binary decision variables resulted in a solution that allocated 0.9999994 of a planning unit to a management zone. I have attached an R script and a Gurobi model file necessary to reproduce the potential bug (reprex.zip), and copied in my session information below. I have posted a question to the Gurobi google groups page to clarify if this is indeed a bug (currently awaiting moderation), and will post any updates here. Until this potential bug has been resolved, I would not recommend using Gurobi 8.0.0 with the prioritizr R package.


Session Information

R version 3.4.4 (2018-03-15)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 16.04.4 LTS

Matrix products: default
BLAS: /usr/lib/openblas-base/libblas.so.3
LAPACK: /usr/lib/libopenblasp-r0.2.18.so

locale:
[1] C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] gurobi_8.0-0    slam_0.1-42     testthat_2.0.0  devtools_1.13.5

loaded via a namespace (and not attached):
 [1] compiler_3.4.4   Matrix_1.2-14    magrittr_1.5     R6_2.2.2        
 [5] withr_2.1.2      memoise_1.1.0    grid_3.4.4       digest_0.6.15   
 [9] rlang_0.2.0.9001 lattice_0.20-35 

@jeffreyhanson jeffreyhanson added the bug label Apr 27, 2018

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jeffreyhanson commented Apr 27, 2018

For those interested, the message I posted to the Gurobi Google Groups can be viewed here: https://groups.google.com/forum/#!topic/gurobi/zDtdl0EEAFU

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jeffreyhanson commented Apr 27, 2018

It turns out that it's not a bug and Gurobi just has a default precision for 1e-5, so I'll update the code to automatically round outputs for binary variables.

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