# Kevin Lynagh challenge

**URL:** https://alloytools.discourse.group/t/kevin-lynagh-challenge/302
**Category:** Uncategorized
**Created:** [November 22, 2022, 1:36pm UTC](https://alloytools.discourse.group/t/kevin-lynagh-challenge/302 "2022-11-22T13:36:35Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![DanielJackson](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/danieljackson/32/80_2.png) [@DanielJackson](https://alloytools.discourse.group/u/DanielJackson)
#### Post date: [November 22, 2022, 1:36pm UTC](https://alloytools.discourse.group/t/kevin-lynagh-challenge/302/1 "2022-11-22T13:36:35Z")

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Just read [this](https://kevinlynagh.com/newsletter/2022_11_organizing_windows/) in Kevin Lynagh’s blog and thought it might be a nice puzzle to solve in Alloy.

> A mechanical engineering friend of mine is designing a system that involves pumping a series of fluids through a column, where, uh, special chemistry stuff happens.
> 
> Each fluid has its own tank and valve, but they’re all slurped by a shared pump, something like:
> 
> A --x–|  
> |  
> B --x–|  
> | |-- Diversion – …  
> C --x–|— Pump —x  
> |---- Column — …  
> where A, B, C are fluid tanks and each x is a valve.
> 
> There are a few tricky constraints:
> 
> Bubbles will mess up the process, so the system must be “primed” before use: Liquid from each tank must be slurped one-by-one and pushed through a diversion line to remove air from the tubes.
> 
> Some fluids conflict with each other (e.g., explode on contact).
> 
> The fluids must be run through the column in a specific order.
> 
> The problem is to find an assignment of fluids to tanks and corresponding priming order that satisfies the constraints. In this toy example, if A and C conflict and the column order is A, B, C, a solution for the physical arrangement drawn above is to first pump C through the diversion, then B, then pump A through the column, then B, then C.
> 
> Of course, my friend’s problem is a bit more complex, with more fluids and additional dimensions (e.g., expensive fluids should have minimal “dead volume” — the length of tube between their tanks and the column/diversion).
> 
> Long-time readers probably have a guess about what technique I’ll try to use to solve this problem, though I’m not at all sure how well it’ll work.
> 
> If you have any suggestions or, even better, want to show me how you’d code up the toy problem above, I’d love to hear!
> 
> I’ll be back next month with (hopefully) a fun solution.
> 
> Until then!