Jach's personal blog

(Largely containing a mind-dump to myselves: past, present, and future)
Current favorite quote: "Supposedly smart people are weirdly ignorant of Bayes' Rule." William B Vogt, 2010

Caches are evil

There's an old joke in programming culture: "There are two hard things in computer science: cache invalidation, naming things, and off-by-one errors."

Up until this year, I don't think I've fully appreciated the first issue of cache invalidation, or cache behavior in general. But over the last few months I keep running into issues caused by poorly thought out cache systems. Some of them my own fault, most of them other people's.

I'm at the point where I'm going to treat anyone who proposes a cache with suspicion, and make sure they can answer all of the following questions clearly. Depending on their answers, there might be no good reason to make a cache right now, or at least not to make the simplest cache with no control mechanisms. As one example, memoization is a neat trick to show off function decorators / macros, but it offers no control over the cache, so you need to know if you're just using it for a trick or for something useful! So, before making a cache of any sort, consider:

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How you might see some of the dead again

The atheist position is that we won't see people who have died again. I don't disagree. But that's not the same as saying it's impossible, with or without the supernatural. There's an actual chance that's greater than epsilon. But it's still very small, I think it would be unwise to hinge any hopes on it, or to mislead (as I think Kurzweil can do) that it's almost assured given better technology.

The supernatural possibility is of course possible. Perfect souls might exist separate from the body and somehow encode all memories and thoughts separately from the brain, perfectly, so that even if the body is brain damaged and lives on another 30 years, the soul, while retaining that, is fully self-aware and has access to all memories and thoughts across all of its existence, and so is unharmed. And it may be that souls are reborn, or that they go have a party together after leaving their bodies, and remember each other (perhaps even across multiple lives if there is some rebirth before the party). Maybe that party's just the pre-party and once enough people arrive they all come back to Earth (some of them having just left!) in new bodies to have the real party. There are many ways, if you grant supernatural possibilities, for you to see the dead again, either while you're still alive or when you too die. Atheists could be wrong. But probably not. So that leaves us with the natural possibility. How might a form of resurrection work?

Is your grandparent the same person they were when they were in their late 20s? If your grandparent suddenly develops Alzheimer's and seems to lose many long term memories, but isn't all the way gone yet, are they still the same person? If they develop into full-blown unable-to-care-for-themselves Alzheimer's, brain cell death and all, are they the same person? If a cure is developed for Alzheimer's before they get to that point, and they receive the cure, so they stop losing long term memories and can form and retain new ones, are they the same person?

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