Martin C Harvey's Pages

We will all be vaccinated and let out of purgatory some time in 2021. Some quick social notes for you folks:

• Look good.
• Be nice.
• No silly magic games.
• Exercise good judgement.
• Show some degree of common sense and initiative.
• Go for older men.

Considering the huge spanner in the works that COVID has presented to the economy and our way of living, What level / frequency of side effects might be considered acceptable?

Vaccine development is usually ultra-ultra cautious, esp if the vaccine developers are not in the same region of the world as those afflicted. Would we accept a higher risk level given the considerable harm presented not only to people’s health, but also their living standards.

Next thing: Are we still vaccinating for the “original”COVID. We now have some more prevalent / trasmissible mutations. Will we get a Vaccine V2 in a couple of years like we do for flu?

So, apart from taking the time to improve the golf swing, I’ve noticed an interesting reticence amongst some people to take certain courses of action. It works like this: People get into a train of thought:

“Well if we do X, then they’ll do Y, or Z, but if they do Z, then it’ll look really stupid and embarrassing, so we won’t do X”.

My question is this: “How do you smack into these people’s heads that the chain of verbal logic they’re going through, bears no resemblance to reality whatsoever.” Here’s why:

• You’re assuming that you know their thought processes. You don’t.
• You’re assuming that they think the same way you do. They probably don’t.
• You’re assuming that the outside forces of nature / chance / unknown unknowns can be discounted. They normally can’t.

And so we get people doing things for political (verbal / thought out) reasons, when sometimes the chain of logic / reasoning bears no resemblance to reality whatsoever.

Half the challenge in life is working out what’s real, and what isn’t.

For example: people who do things like PR / Advertising. The effects of PR / Advertising / Setting up a movement are statistical. That is, you’ll either convert some people to the cause, or your won’t. Convincing yourself that you can convert any one individual, or that you can rationalise individuals actions based on a widespread (relatively) nonspecific set of information or disinformation is false.

I’ve noticed that people get better at this as they get older. People in the 20-35 age bracket are really poor at telling what is genuine information from what is just hearsay, PR and disinformation. Or more particularly, even if they can verbally reason these things through, their behaviour is governed more by the group understanding, than the underlying realisty. They overestimate the credibility of hearsay, and the importance of groupthink, and they underestimate how important it is to check the facts and/or reality of the specifics. Hence: “my mate says that X” … governs their behaviour more than “x is true”.

Call me a rationalist.

So, I did a bit of reading, and wrote a little solver. Will solve most puzzles instantly, and all puzzles with a unique solution in under thirty ten seconds. Not bad for a days work. Doesn’t even need multiple CPU cores.

I notice that Knuth has a clever way to do it a thousand times faster. I have not represented all the constraints explicitly….

My solver is here.

Before:

After:

Answers to questions:

• Yes.
• Not necessarily, but for human solvable problems, the decision tree is pretty constrained. There may be heuristics I don’t know about.
• Depends on initial constaints, sometimes yes, sometimes no.
• That’s the next big thing I have to figure out. It looks much more tricky.
• As one passes the point where there is not enough information to find a unique solution, for every digit you remove from the initial configuration, the solution space goes up by a factor of between 10 and 100 roughly.
• With no initial constraints, taking symmetries into account, the state space is five billion. Not taking symmetries into account it’s one trillion times that again.

• Is there an initial configuration of the board which looks sensible, but has a logical inconsistency so there aren’t actually any solutions.
• In the puzzles posed by newspapers (at least the easy ones I have done), there is normally always a fully constrained position for every next move. Is this always the case?
• If there isn’t a fully constrained position for every next move, are all subtrees except one blind alleys, or not?
• How does one generate a puzzle where one knows that there are always enough constraints to make a reasonably unambiguous decision?
• In the case of underconstrained configurations how large is the state space?
• In the case of no initial constraints (no numbers at all), how large is the state space of all possible solutions?

Looking at making further progress on my DB engine. In no particular order:

• Case insensitive string indexes. DB needs to be able to handle changes in index order.
• Removal of current index tag scheme, with more complete “index combobulation” info, able to handle more than just A-B buffering.
• Complete transactionality, where metadata and data changes can be done in one user transaction: each user transaction consists of multiple changesets. It should then be able to roll forward / roll back multiple sets of changesets to support existing commit / abort functionality. (Pipeline depth).
• Support for multiple transactions in progress at the same time: instead of A-B buffering, we have Current (Next1, Next2, Next3) buffer sets. Amount of concurrency can be specified at transaction start time. (Pipeline width).

Once I’ve got all that done, then it should be possible to wrap the local DB logic into a distributed database. This will require a “journal of journals”, indicating the various transaction history paths that each each copy of the database has gone through. Depending on consistency level required, you could then do “last write wins” or “cascading abort” semantics, depending n what you want to do.

Hi guys!

So I have now made a little check-in app. It asks you to register your e-mail and a contact e-mail. Once you’ve done that, you need to login or use the quick check-in link once per day. If you don’t (maybe coronavirus has got you, or you’re not well), then it automatically sends a mail to the contact address you specified.

You can try it out here.

N.B Some web browsers will complain about “invalid security certificate”. I like encrypting and keeping your passwords safe, but can’t be arsed to register the website certificate just for a demo, so if you want you proceed, click “Advanced” or “Details”, and then “Proceed to website”.