Sometimes, when I interact with other human beings, I realize that their way to think about the world is radically different from mine. To put it differently, I have a few weird opinions with a long chain of logical consequences which I take for granted, and I sometimes discover that people just don't think that way. I tend to be quite surprised when it happens, all the more so because superficially, other people and I tend to behave in the same way and can communicate quite easily. I'm always amazed by the fact that human beings probably all have a very different view of the world, but still manage to implement with very few glitches the interface required by society.

Hence this blog: by explaining things which seem obvious to me, and trying to find out why they seem to be so, I hope that, perhaps, if you believed them to be not obvious but plain wrong, you will think them out and realise that they could be true (because they are, since, as I perhaps forgot to mention, I'm always right). This is, of course, a reasonable goal: it is a well-known fact that people tend to change their basic mental beliefs by reading some random twenty-line ramblings.

Information should be distinguished from its support, but most people seem unaware of this distinction. Here are two examples:

Books.

When someone says that they love a book, it can indifferently refer to a sequence of letters with some interesting properties, or to a pretty object with a nice leather cover and a pleasant smell. A book with blank pages can be a very pleasant object; likewise, you can read and enjoy a literary masterpiece even if all you have is a cheap paperback edition. The advent of ebooks will probably force people to understand this difference...

Postal mail.

People indifferently use mail to move physical objects around and to transmit information. While the first activity probably won't disappear any time soon, the second one has been obsolete for quite some time now, because sending beams of light through optical fibers or pushing electrons through wires is incredibly more efficient. Yes, I am aware that the postal service has an unexpectdly large bandwidth if you use it to move hard drives around, I don't mean to criticize the rare people who might be using it in that way; the thing I find depressing is that even today, massive important services like the government still need to carry pieces of paper across the country to send me data. (I am also perfectly aware of the security and reliability shortcomings of email, thank you, but there are ways to make things work.)

Interestingly, what I'm saying doesn't apply to music and movies anymore; people seem to have understood that these things can be stored in a hard drive rather than in a pile of physical artifacts. The same should happen for paper mail and books some day...

I'm trying to find out if the following problem is already well-known in computer science...

Consider 2×N politicians and N TV channels. We would like to compute a schedule for N time slots such that:

• During each time slot, each TV channel broadcasts a live debate featuring exactly two politicians. This means that for each time slot, each politician appears on exactly one channel.
• At the end of the N slots, each politician has appeared on all channels. This means that for each politician, each channel is scheduled to exactly one time slot.
• No couple of politicians debated more than once. In other words, over all the debates which took place, each featured a different couple of politicians. [Notice that, since there are 2×N choose 2 couples of politicians and only N×N debates (one debate on each of the N channels for every of the N time slots), some couples of politicians will never debate.]

This problem is quite simple and has occurred at least once in practice (thanks Yannick!), so I'm wondering if it has already been studied. Maybe it is well-known, but under some weird name ("Martian elimination problem"? "Yannick's mother's problem"?), or maybe it is just a special case of some well-known generic problem. (I tried to find a simple graph-theoretic formulation, for instance, but failed.)

Actually, it seems that this is very similar to Kirkman's schoolgirl problem and the Social Golfer problem: to be more precise, I think that my problem is the social golfer problem for g = N, s = 2 and w = N.

In the meantime, since I wanted to find out if some solutions exist (and, if yes, what do they look like), I wrote a crappy C program to find solutions using backtracking. It turns out that this simple strategy finds solutions for N < 11 (apart from the special case with N = 2). For larger values of N, no solutions are found in a reasonable amount of time (though one would expect solutions to exist).

Here is one possible solution for N = 8. Each line is a time slot, each column is a politician, and the values in the cells are the channel on which each politician appears at each time slot. There may be a simple pattern, but I can't see it.

 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7
 1 2 0 2 0 1 4 5 3 5 6 7 3 7 4 6
 2 1 2 0 1 0 5 4 5 7 3 6 7 3 6 4
 3 4 4 5 5 6 0 1 7 6 7 0 1 2 3 2
 4 3 5 6 7 3 1 7 6 0 0 2 2 4 5 1
 5 6 7 3 4 7 2 6 0 1 2 3 4 1 0 5
 6 7 3 4 6 5 7 0 1 2 4 1 5 0 2 3
 7 5 6 7 3 4 6 2 2 3 1 4 0 5 1 0

It would be quite funny to generate incomplete solutions to the problem (that is, grids with some cells left empty, for which we know that they can be legally completed in only one way). You would probably get something akin to sudoku...

A similar problem is discussed here (in French); search for "Quelqu'un qui assistait à cette réunion".

I sometimes wonder what it would be like to learn your own life by heart. Let me explain what I mean with this weird expression. I've been keeping a diary for some time (since January) in which I just write a quick summary of what I did every day. In practice, I use this diary as a way to be able to find back, a few years from now, what I did on a specific day (it might prove useful in a somewhat bizarre set of circumstances), or as a way to re-read what took place quite some time ago (whenever I feel nostalgic, or just curious). But in fact, my deeper motive in writing this diary is as follows (it's quite simple, in fact): I find it really sad when I realize that I haven't the faintest idea of what took place in my day-to-day life a few years ago and that I have no way at all to find out. Of course, it's impossible to write down everything that took place, but just having something to start with (which often conjures more memories) is already a lot.

If you start to think about this kind of diary using computer science terminology, you could see such a diary as a way to sort memories using time as an index. Indeed, if you start searching for memories in your brain, you realize that you can easily find them thematically, but that it's nigh impossible to find them chronologically (except for the very recent past). My diary could serve as a way to circumvent this problem. (An external way, which I keep on my computer rather than in my brain.)

Which leads to my question: what would it be like to learn such a diary by heart, as it is written, and to be able to recite it like a poem? I'm not thinking about learning the exact wording of entries (although it could be a way to start things off), but to learn the succession of events, and to be able to remember one day after another, in order, over a long period (ideally, the whole of one's life).

The thing I find seducing with this idea is that it is deliciously meta. How natural and canonical to learn your own existence by heart! And how weird to remember not only real events, but also the act of memorizing real events, and the act of memorizing the act of memorizing, and so on...

If you follow this objective to its logical conclusion, you would spend most of your time thinking and trying to remember the sequence of your thoughts, and trying to remember that as well...

Even in a less perfect way, having some period of your life which you learnt by heart and can remember chronologically much later would be quite cool. I don't think I'll ever take the time to do it, but I wonder if someone already did something like that...

Related: hyperthymesia, the condition of having unusually good autobiographical memory.

Very related: Lembransation, a blog describing a project to remember every day in the blogger's life, spanning across a period of 10 years (last updated in 2022).

Just a quick rant about the fact that many users (including people who should know better) seem to have some sort of belief that computers (especially laptops) are not meant to stay powered on for extended periods of time, and that doing so isn't normal use and is likely to damage the hardware.

Needless to say, I don't agree at all with this view. In my opinion, non-faulty hardware should be able to withstand maximal load for arbitrarily long periods of time. To say things differently, if a computer fails under such circumstances, it isn't normal: it means that the computer isn't working properly.