Re: Off-by-one error when solving integer linear program

Ah, I just realized that you only see Part 2 if you're logged in and have
solved Part 1.

The goal of Part 2 is to maximize production of the FUEL element, starting
with 1 trillion
units of ORE; that's the problem that I'm solving in my LP file.

Since each reaction occurs an integer number of times (and both consumes and
produces an integer number of reagents / products), the answer should be an
integer.

-Matt


On Tue, Dec 17, 2019 at 11:40 PM Michael Hennebry <
[email protected]> wrote:

> On Tue, 17 Dec 2019, Matthew Keeter wrote:
>
> > 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.
>
> As noted elsewhere, an upper bound of a trillion
> requires more precision than GLPK will normally require.
> I do not get an integer objective.
>
> I'm really confused about what problem is being solved.
> The given ILP does not resemble the problem of producing one unit of fuel.
> For the puzzle data I found, one would have 59 variables (columns),
> one for each reaction.
> I saw mention of more than one part,
> so I expect I am missing something.
>
> > 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.
>
> The correct answer is 82,892,753.14  .
>
> --
> Michael   [email protected]
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