Steven's Weblog

I’m working with someone to fix a bug in some code. I want him to be able to actually do the fix, and in the process, learn more about the code base. He’s taking over a project from me that I’ve been working on in isolation for a year or so, so the priority is on shifting the knowledge from my head to his rather than immediately fixing the bug.

I think I have a fix (which I developed in the process of trying to explain the code), but just handing it over wouldn’t achieve the goal of giving him the deeper understanding of the code that he needs going forward (I still offered him the option; we’ll see what he thinks). The fix only affects about three lines of code, and it probably would have taken me about 45 minutes to find and fix myself. But explaining the whole context of the code, and precisely how it was that I screwed up in the first place, that’s a lot more work. I spent 3 hours trying to document the meaning of one relevant variable, and I still feel like I didn’t do a great job of it. It will be at least another couple hours of work to describe exactly how I fixed the bug, if he wants to hear it.

This might be one of those cases where he’d be better off refactoring the code. Sometimes people use refactoring as a way to gain deeper understanding of the code, as well as making it easier to understand in the future. In this case, for example, I wrote a function called adjust-rowspan-vec, which probably should have been named update-rowspan-vec-for-next-row. Though the name rowspan-vec in itself is not all that clear, but ugh, it’s hard to find a good name for that one; maybe data-for-cells-which-span-rows-and-are-currently-in-flight-so-that-we-can-track-where-to-insert-dummy-cells-as-we-scan-down-the-input-rows, or something. So, yeah, probably needs a refactoring, just so that we can better wrap our heads around whatever concept I was trying to express with rowspan-vec.

It’s hard to describe the concepts in use in the code even if it was working properly, but to describe my partially-broken mental model when I wrote the incorrect code would add another level of complexity. I think I could do it, though, and it’s awesome that human languages have the ability to express such deep weirdness.

[And just to vent a little more, none of this is made any easier by the fact that the code in question is in a functional language, which means we’re using immutable variables and two levels of recursion rather than mutable variables and loops. Nor is it made easier by my lack of confidence in communicating in English with someone whose first language is not English…]

Jayson was asking on Twitter whether anyone knew where to get pins like the ones on Basic Stamps. I wasn’t able to help him, but I did have fun looking around at the catalogs of Mill-Max, TE Connectivity, Interplex, and Keystone. There are a damn lot of connectivity solutions out there!

Sparkfun did have a couple interesting forum threads about these, here and here, and at Mill-Max, I found something close (though that doesn’t lead to any small-quantity distributors).

Anyway, when I was looking at the Basic Stamp, it popped into my mind that maybe one could save some hassle in doing home prototyping of 2-layer PCBs if one could route vias out to the edge of the board and use clips at the edges, rather than drilling and using rivets, wires soldered on both sides, etc. But then I realized that such a scheme is like trying to lay out your graph on a sphere rather than a plane, which leads to no advantage, as is well-known in topology. Topology is good for something, eh?

Thinking along those lines, though, makes me wonder about other methods that might yield some advantage. For example, route out a hole in the middle of the board and clip traces on those edges and you’ve got yourself a torus, which does (I think) get you more flexibility. It might be fun to do an investigation of graph embeddings in a variety of physically-realizable connection schemes, with an eye toward finding some method that is easy for a home prototypist given some small catalog of techniques and pre-manufactured connectors. There’s probably some paper written by Euler when he was 7 that lays this all out, so I suppose I should hit the library and brush up on my topology…

After reading The Milo Criterion, I was reminded of a thought I had a while ago:

it’s one thing to say “oh, that soup i just made from some random ingredients turned out really well.”. it’s another thing to throw up the recipe on your blog and let people put it together themselves. it’s yet another thing, though, for the entrepreneur to turn that into a can of soup that millions of people can buy for $0.99 as just another option in the soup aisle.

After I wrote that, I had a feeling that there was something odd about my use of the word ‘entrepreneur’ there. I think it’s that the average entrepreneur wants to think that their product is so radical that it wouldn’t fit in the soup aisle. It has to be in an end-cap display with a space cleared out around it so that people fainting from joy won’t hit their heads on shelves.

Maybe your thing is so radical it can’t rightly be called soup any more. But there’s quite a bit of marketing power in being on the shelf next to the soup, such that a customer in the soup aisle can use existing decision processes to decide on your product. If it really is a significant departure from soup, customers will tell you (and others) that, and they’ll work with you to define a new category. That’s probably a lot easier than trying to define that category ahead of time and then drag people there with you.

I’d like to work on rescaling the economies of scale. Let me start with a brief look at what’s meant by ‘economies of scale’. This is very simplified, and we could talk for days about different nuances and exceptions and such, and if you want to start that conversation, I’m up for it. But this model will suffice for me to explain what I mean by ‘rescaling’.

For any given product, we can find a number of ways to manufacture it. (A rubber ball can be fashioned by hand-kneading and rolling a bit of rubber, or by injection molding.) For each method of manufacture, we can separate costs into two buckets: setup and per-unit costs. (Hand-rolling balls has basically zero setup costs but pretty high unit costs, injection molding has high setup costs but quite a bit lower unit costs.) These costs mean that for any given product, there are a number of regimes, under each of which a particular manufacturing method is most economical.

So, at its simplest, the concept of rescaling the economies of scale means using the same ingenuity we use in devising those different methods of manufacture to improve upon the tools which are part of those methods, as well. We figured out how to make rubber balls cheaper by using injection molding, now let’s figure out how to make setting up molds for new products cheaper, too.

And of course, we do that. At least, whenever a production process is not completely vertically integrated, and the product is under competitive stress, then there are separate firms making tools for the process, and they are subject to competitive pressure to reduce their prices. The successful ball maker will seek and find cheaper alternative vendors for the mold making process.

So, not necessarily a radical idea, looked at that way. It might be a little more radical to say that my reason for wanting to rescale things is so that smaller producers are empowered to use more sophisticated production methods for smaller batches. To shrink the gap between the concepts of ‘prototype’ and ‘small production run’. To help bring the promise of mass customization to fruition. To allow more people to scratch their own itches. To give more little ideas a chance to come to life without having to appease the mighty powers of capital. OK, that last one is probably skirting radical, so I’ll stop there for now.

I just subscribed to a new, paper, magazine (Circuit Cellar, if you wanna know). This is odd, because I don’t much like paper*, especially with ephemeral content like magazines.

But I think I know why I did. Paper magazines, after I’m ‘done reading’ them, become totems. Of what I was, or want to be, or want to do. But like any such totems, they can sorta disappear into the background of my perception after they’ve laid around the floor for a few days. Magazines, though, come again fresh every month, on someone else’s schedule. So I think I got the subscription mainly to help establish habits that I want to establish.

Or, whatever. I probably don’t actually know why I do things.

(* The fact that I have a couple thousand pounds of books does not contradict the assertion that I don’t much like paper. Deal with that as you must.)