Scary stuff

Possibly the scariest diagram anyone will ever have to look at. It’s even less penetrable than that Eric Levenez history of unix thing.

Posted in objc foundation | 2 Comments

Sacrilege!

As I wrote the @interface to an object today, I found myself wanting for but one thing:

- (NSArray <MyProtocol> *) foo;

Where – as if you hadn’t guessed it – the pointy bracket bit (the lengths to which I go to avoid typing out HTML entity names) would specify that all of the objects in the array returned by -foo conform to @protocol(MyProtocol). I then realised that this wouldn’t be quite as useful as I might think, but also decided that it wouldn’t be too hard even on the existing ObjC runtimes to come up with a nightmare function such as:

(Protocol *) objc_class_to_protocol(Class *cls);

…therefore meaning that my hitherto unattainable pipe dream:

- (NSArray <MythicalNSStringProtocol> *) foo;

may indeed be somewhat closer to realisability. Of course, with all of this being compile-time type checking (as with the similar beasties on Java) there would be no need to frob the runtime.

Update 2007-01-26T13:22: yes, I realise that the snippits above read "an NSArray or subclass, which also conforms to the MyProtocol protocol". I also know what I mean.

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Eating one’s own dog food

I feel foolish for having made this error (especially after having so patiently explained how this stuff works on Mach), but today I did it. I reported the amount of free memory on a Linux system as being the amount reported by free as free.

My own opinion on this is that I suffer from a view of hardware management which was tainted by using micros like the Dragon 32 (Radio Shack/Tandy TRS-80 to my American readers) and the Amiga, where there were basically two types of memory usage: yes and no. A particular block was either in use by the system, or it wasn’t. On the Dragon 32 it was even easier than that of course; all bytes were available for reading and writing, but what happened was context-dependent. Also because this was the MC6809E, whether such a peek/poke made sense depended on whether you were trying to hit an I/O address, and what was plugged in. The Amiga had a particularly lame memory allocator which quickly sucked performance like a vacuum of performance suckage +2; but a byte of RAM was either in use or it was available.

But I digress. The point is, that such a simple view of memory availability is no longer sensible but it’s hard for me to think around it without a lot of work, just as it was hard for me to become a programmer after I’d been taught BASIC and Pascal. If I were involved in UNIX internals more (and indeed that would be fun, although I think maybe Linux wouldn’t be my first choice to open up) I’d probably be able to think about these things properly, just as I had to throw myself into C programming in a big way before I lost my BASIC-isms.

For the record (and so that it looks like this post is going somewhere), both operating systems have an intermediate state for RAM to be in between "used" and "not used" (where I’m ignoring kernel wired memory, and Linux kernel buffers). On Mach, there’s the "inactive" state which I’ve already described at el linko above. On Linux, it’s used as an I/O cache for (mainly disk, mainly read-ahead) operations. This means that Linux will automatically take almost all (if not all) of the memory during the boot process. The way that inactive memory gets populated on Mach means that on that system (e.g. Darwin) actually the amount of free memory starts large and inactive starts small, but over time as the active and inactive counts go up, the free count goes down, and it’s rare for memory to be re-freed. On both systems, free memory is really "memory it wasn’t worth you buying" as it’s not being put to any use at all.

Posted in kernel, linux, mach | 1 Comment

客観的なc計算機言語

Just heard from someone who wants to translate the c.l.o-c FAQ into Japanese. Sweet!

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Copyleft

It is complete:

I no longer even own all the code I write in my spare time, on my own equipment.  :-)

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TGD – John on acid

I’m about halfway through my OmniOutliner document of notes made while reading TGD now….

There’s a paraphrase in TGD saying that if the epistles of Saint John the Apostle represent John on pot, then the book of Revelation is "John on acid". What makes this observation more interesting is that it may be literally true – or at least closer to the mark than the quip may at first appear.

There was a documentary by Tony Robinson on Revelation and the End of Days, called The Doomsday Code. The – frankly worrying – sentiments of some of the extreme christian right in America are the same as described in TGD; namely that the Middle East instability [inclusive] or global warming or the 2005 hurricane season herald the proximity of the rapture, and that rather than doing anything to help those caught up in these situations we should be actively encouraging the Apocalypse, and xtians should let their heathen friends know that, well, they told us so. In the course of describing modern End Timers, the documentary showed us where Revelation was penned.

There are tens of apocalyptic visions penned by post-Christ Jewish theologians, but only one has been included in what is now termed the canon of the New Testament. That book of the revelation of Jesus Christ to his disciple, John (which isn’t accepted by the Eastern Orthodox as part of the divine liturgy) was written on the Greek island of Patmos sometime in the second half of the first Common Era century, and details two visions experienced by the John of the title (whether or not he be apostolic) while on the island. The other key fact to remember about Patmos is the abundance of fly agaric mushrooms, especially around the mouth of the cave of revelation.

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TGD – begging the question

Many of the arguments pro-religious belief presented in TGD would form a nice corpus in a dictionary of critical analysis for the entry on "begging the question". However, Prof. Dawkins studiously avoids the phrase despite its rampant, repeated and some would say wanton applicability, and if I were ever asked to predict why (I haven’t been, I just like the sound of my keyboard) I’d say that it’s because the phrase is so frequently misused on both sides of the Atlantic ocean.

Indeed, when I was taught the phrase, the example I was given is that of proof of the existence of god: we can see the results of god’s creation all around, therefore god created them, therefore god exists. That’s about as short – and absurd – an example of the technique as can be demonstrated. In ordinary speech, people use the phrase "begging the question" to mean: the argument I have just heard is incomplete or fallacious, because it appears not to answer (or to directly raise) the following problem. Where the problem was not explicitly part of the argument. However, the meaning of the word "beg" should not be overlooked, and is key when calling an argument out as one that begs the question. In fact, it isn’t the argument that begs the question: it’s the conclusion which does so, and the conclusion is begged from the question. In other words, the meaning of the phrase is that an argument draws to a conclusion which already existed in its assumptions or axioms. My Latin isn’t very good, but I might describe this kind of argument as QEQ – Said that which was said.

Let’s look at, for example, the argument for the existence of purgatory (it’s quite near the end of TGD which makes it easy for me to remember). The conclusion is that purgatory exists, and the justification is that people everywhere are praying for the souls of the dead because they believe that the souls are in purgatory, and surely prayer isn’t pointless. I hope that going all slanty made the point in the argument where the conclusion was codified apparent – the reason we can be sure that purgatory exists because we are sure that purgatory exists. QEQ.

I realise that this had little to do with the thesis of TGD, but to beg the question is a cool phrase which should be used less, but with higher accuracy.

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TGD – I’m not dead yet!

The title of this article is a quote from Monty Python and the Holy Grail – the body cart comes around the town to collect up the (presumably leprous) corpses, and along comes John Cleese with his ninepence and his cadaver. The only problem is that actually the corpse feels rather like he might pull through.

This is a situation which relates to the ever-decreasing sphere in which divine intervention can be invoked, such reduction being due to scientific advances. There are known cases where people have been thought dead and have "got better", or have been ruled out a long time before the actual event of their dying. As an example, a death through epilepsy can often cause the unfortunate to become unresponsive long before becoming dead, so that ‘miraculous’ events such as the body remaining warm for days after the death are recorded. While the meaning of the term "dead ringer" has nothing to do with the 19th Century safety coffin, such devices did exist. The whole purpose behind holding a wake was the hope that life might return to the deceased – because sometimes it did. Various poisons can lead to the body attaining a death-like state, while in fact the subject remains living; perhaps the most famous of these is TTX (the toxin carried by pufferfish); supposedly used by Vodou practitioners to create zombies. A good explanation of that is Ghosts, Vampires and Zombies: Cinema Fiction vs Physics Reality. The case of Wilfred Doricent, described in the arXiv paper, is recent: he died in March 1988 and was no longer displaying many of the symptoms of death by September 1989.

The point here is that there are modern cases where death is misdiagnosed. Given the modern equipment, techniques and advances in both theoretical and practical knowledge, one would assume that the rate of misdiagnosis of death has decreased over time (and in a related vein, the number of conditions which terminate terminally has decreased, too). How can we know, without even contemporary doctors’ notes, whether a particular resurrection event was miraculous or just a case of mistaken interment? Pufferfish aren’t particularly common around the middle East so perhaps Lazarus wasn’t eating fugu but he may have had epilepsy, tetanus or a number of other conditions which were confused with fatality.

Returning to the parenthesis on terminal conditions, above, one can argue by progression that if there are fewer "terminal" conditions now in (kindof) 2000 than there were in 1800, then assuming no catastrophic dark age reversion there will be even fewer in 2200, fewer still in 2400 and so forth. So the ability to "miraculously" recover from a terminal condition should decrease over time too; not because the rate of miracles is decreasing but because the ability to explain the circumstances is increasing.

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TGD – religion leaving the gene pool

If there was some kind of selection pressure which favoured, even in a roundabout way, predisposition toward religion, and if sexual selection naturally favours successful people (or those who exude success, anyway), then we have a (not too serious) quandary. Because the most high-profile adherents, the most apparently successful at religion, are often the clerics. Who are frequently celibate (or at least, are required to be: please do read the dictionary definition for nepotism though).

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TGD Responses – selection for religion?

I’m going to do a few articles based on The God Delusion by Richard Dawkins. As this is a bit of a departure from the usual content of yon blog, I’ll be sure to prefix the titles of each with TGD so that those so inclined can filter for/against them in their syndication readers. The articles will be a mixture of prose agreeing with parts of the book, arguing against parts, questions which the book made me ponder and for which I have no answer, and quips (I haven’t yet decided whether to group these together or allow a post for each) answering specific ideas or even sentences. My only hope is that all of the articles – and the processes leading to their inception – are critical, in what I hope is the obvious intention of that word. Needless to say, I’ll leave the punchline – my opinion of the binding theme of TGD and any changes it has had or not had on my views – until the final article.

I’ll start this series by looking at his idea of religion having its roots in a "misfiring" of some advantageous trait which has been selected for. I would ask this question: why should that be so? In his description of evolution he explains the idea of a neutral mutation — one which overall has no positive nor negative effect on the fitness of the genome, but which can nevertheless become dominant (or at least prevalent). For instance, human earlobes either join at the bottom of the lobe to the face or they do not. I don’t understand there to be any fitness advantage in either, yet at some time the allele(s) associated with earlobe stuck-to-facedness have, I presume, diverged from a common variant. Why couldn’t theism be just one type of earlobe? What if the mean fitness of religious nonreligious "phenotypes" (I expect that’s the wrong word…perhaps theotype is better) are not significantly different, and religious behaviour just happens to arise and have become common? I suppose there may be an answer to this, although if there is it wasn’t presented in TGD.

There is a related argument in the book which I don’t buy. In dismissing the idea of a straightforward selection pressure for evolution, Prof. Dawkins presents the Gedankenexperiment of a tribe who worship a war god, and whose religion dictates that they should go and fight the neighbouring tribes, in the course of which they acquire of course the resources of those other tribes, and propagate their seed further. The argument presented against this is that for any one individual it is more efficient to hang back while their companions do all the fighting, then to share a part in the spoils. Therefore the society would collapse, as no-one would want to do any fighting. This rather squarely misses the point of, for example Freya’s D.Phil. thesis and the concept that a population based on cooperation (in this case the war-tribe, in Freya’s case a biofilm) can in fact tolerate some fraction of "cheats" and that there is a stable state where proportion of cheats is non-zero but the population still thrives. Consider the British benefit system — some non-zero amount of money is spent on targeting benefit fraud, which keeps the fraud not at zero but at some level which both can be afforded and which leaves the spending justified. In fact, a canny war-tribe member would try to weasel their way out of the line of combat by arguing (rightly or otherwise) that they alone have some property that the average combatant does not possess, and would refer to the weaseling as "promotion" or officership.

Another potential explanation is an interpretation from Terry Pratchett, Jack Cohen and Ian Stewart’s Science of Discworld series. In it, they describe the idea of "lies-to-children" in which various layers of falsehood are peeled back as a child becomes ready to accept the more complex, yet more accurate, explanations. What if this idea is extended to become lies-to-protoscientists? What if, as well as a moral Zeitgeist, there is a consensus of acceptable sophistication? So a society initially agrees that each tree, waterfall, star, planet etc. must have its own god, then finds that it can accept the god-of-concept ideas of the more recent polytheistic disciplines, then agrees that a single god, while more complex a solution, is palatable, all the while science is also working to provide the ultimate in sophisticated solutions: that which is born out of simple concepts, but which can be applied to give predictable and verifiable results.

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