Hi folks, I used GLPK to solve a problem in this year’s Advent of Code [1], and noticed that it produces a very slightly wrong answer for one of the examples.
It’s an integer linear programming problem, pasted below the fold in CPLEX LP format. The correct answer is 82892753, and I’m getting 82892752. I’ve pasted my glpsol output at [2] Strangely, other folks have gotten the correct answer with the same input; there’s a reddit thread discussing it at [1]. I'm on a Mac OS 10.13.6, GLPK 4.65, GMP 6.1.2, compiled with Apple LLVM version 10.0.0 (clang-1000.11.45.5) Any ideas? Regards, Matt Keeter [1] https://adventofcode.com/2019/day/14 [2] https://www.reddit.com/r/adventofcode/comments/eafj32/2019_day_14_solutions/fawjrgr/ [3] https://gist.github.com/mkeeter/1b4f5a5a89014fdc9e80f43187788436 -------------------------------------------------------------------------------- Maximize out: produced_fuel Subject to NZVS: 5 equation1 -29 equation3 -7 equation9 >= 0 ORE: -157 equation1 -165 equation2 -179 equation5 -177 equation6 -165 equation8 +1 consumed_ore >= 0 DCFZ: 6 equation2 -7 equation7 -3 equation9 >= 0 FUEL: 1 equation3 -1 produced_fuel >= 0 XJWVT: -44 equation3 +2 equation7 >= 0 KHKGT: -5 equation3 +8 equation9 >= 0 QDVJ: -1 equation3 +9 equation4 >= 0 GPVTF: -9 equation3 -1 equation4 +2 equation8 >= 0 HKGWZ: -48 equation3 -12 equation4 +5 equation6 -5 equation9 >= 0 PSHF: -8 equation4 +7 equation5 -7 equation7 -10 equation9 >= 0 ore_consumption: consumed_ore <= 1000000000000 Integer produced_fuel consumed_ore equation1 equation2 equation3 equation4 equation5 equation6 equation7 equation8 equation9 end
