Assorted stuff

My wallet got significantly lighter today, although I tried hard to get as much as possible. For the last several weeks I've been writing this scirpt (don't follow the link, it is still a very scruffy version) to optimise my expenses. The script takes a BOM and a list of products available in shops and tries to find a subset of products that provides all materials needed (BOM) and is the cheapest including shipping. The first version I conceived was O(2ⁿ) CPU-wise, where n is the number products. With n around 40 this problem becomes practically unsolvable (at least in Python).

The second approch was made possible by a teammate of mine who gave me a dynamic programming algorithm that flips the problem and makes it O(p * 2^m), where p is the number of products and m number of BOM entries (times the amount of materials, e.g. ten servos of the same kind increase m by 10 unless you declare that shops provide them in 10-packs). The first version of this alogrithm didn't count shipping (which may significantly change the solution, I saw it after my running my binary tree traversal algorithm for about twenty four hours). Unfortunately adding vendor-dependent shipping costs means (at least now) iterating over all subsets of vendors (2^v). The script finishis its job in about two hours and with some more work it could run in parallel but it still can't be declared scalable. I am going to build a few other things this year and hopefully I will find some time to improve the script (we've alread got an idea of an algorithm being quite fast though a lot more memory hungry).

This post was supposed to be about the plane(s) I am going to build and not about the software I wirte. Let's what I am going to find in my mailbox soon.

This isn't exactly what Mikey was promising ($10 RC plane). I suppose, however, he's got sutff worth a lot more thant taht in his drawers.