Random ramblings

Wednesday February 01, 2006

Real life memento

Via a slashdot article on memory loss, I came across this account of life without memory.

new twist in 419 spam

Email '419' spammers (i.e. the "PLEASE HELP ME MOVE $MILLIONS" kind) must be feeling the pinch. I received one this morning, from malaysia via postal mail!

Wednesday January 18, 2006

Asimov's "The Last Question"

I'm a fan of Asimov, though I havn't read anywhere near enough of him. I only discovered his short story "The Last Question" the other day. One of his best stories, according to the author himself, well worth reading.

Linux on Niagara?

David S. Miller, the Linux UltraSPARC maintainer, received a wee gift recently...

Saturday December 31, 2005

The KLF Manual

The KLF Manual, or How To Have A Number One - The Easy Way" is a fun read, based on their experience getting their memorable classic, uhm, "song", "Doctorin' the Tardis" to number one, released under the name "The Timelords". Who could ever forget those lyrics?

Exactly why Tom Robinson is hosting this full copy of the book on his website is a mystery. He doesn't appear to have any connection to the KLF, least not one I can find that'd allow him to distribute this kopyrighted book freely. My guess is the KLF must have sampled one or more of his tracks, and so he feels justified in returning the favour in kind.

Let's hope all copies of that book are destroyed, before it's used to inflict more pain and suffering on the world (e.g. like "edelweiss"). The JAMs other slightly more serious stuff, e.g. "The White Room" is sort of worth listening to though.

Wednesday November 30, 2005

C'etait un Rendezvous

"C'etait un Rendezvous" is a 1978 short film by Claude Lelouch of a car driving through Paris, by an unknown driver. By common repute the car is a Ferrari 275 GTB¹ and reaches speeds of over 220km/h² in the film. The speed claim is endorsed in this analysis by some students.

The 220km/h claim doesn't seem right though. Go and watch the video, watch it like you would watch the road normally when driving, try and identify hazards and traffic lights as early as possible at least and think about what you would do as a driver (if you had licence to drive so recklessly). Do that before reading the spoiler in the next paragraph.

It doesn't feel that fast, does it? Even on the long stretch from l'Arc down to Place du Concord, you still have plenty of time to see traffic lights, even other traffic. On the stretch after Place du Concord to the Louvre (169s to about 200s), where the speed analysis linked to above claims the highest speed of 220km/h is reached, other traffic on the road is seen with plenty of time to spare and even the armchair observer watching the video has time to think "better change lane to avoid that car". It does not feel at all like 220km/h.

So out of curiosity, and with scepticism, I had to try to verify the 220km/h speed between 171s and 189s of the link above. Using this image from Google maps the distance between the first and second bridges after Concord, shortly after which the car turns into the Louvre, is about 430m, according to scale given (the section of road is highlighted in white). The distance between Concord and the first bridge is noticeably shorter, but call it 400m. According to the analysis above, the distance between 171s (after Concord) to 189s (well before the second bridge) is over a kilometre, 1.1km. However, according to Googles' satellite image, it's less than 800m.

The average speed, using the Google image scale, from where he turns onto the road after Concord at 169s to the first bridge at 181s is:

400/(181-169)*3.6 = 118km/h

From there to the second bridge at 195s is:

430/(195-181)*3.6 = 108km/h

So, if Googles' sense of scale is to believed (and apparently they know how to scale ), the analysis above is incorrect and, at least by this methodology, the 220km/h is disproven.

Of course, Google could be wrong and the data the students used could be correct. However, we can estimate the speed of the car by measuring the relative speed as he passes the two cars by the second bridge. The first car looks like a Renault 5, the second is a Citroen 2CV and appears to be, at most, 5 car lengths ahead of the Renault 5, so about 18m at most. The car in the film takes 3s to pass the 2CV after passing the Renault:

18/3*3.6 = 22km/h

The convenient factor here is that a 2CV struggles to get much past 100km/h. Which would, assuming the 2CV is near to flat-out, put the speed of "our" car at roughly 125km/h maximum. This figure consistent with the speed of 108km/h derived from the Google image data, and strongly suggests the 220km/h analysis must be flawed.

It is quite possible the car reached higher instantaneous speeds after Concord before it reached the Renault, say at around 181s, but that's not what the analysis linked to above tried to measure, and even then it seems highly unlikely to me those speeds were anywhere near 220km/h. You could calculate an estimation of this by measuring the rate of increase in apparent size of the Renault 5 as it first appears in the distance and some basic geometry. I suspect that too would work out to between 120km/h and 140km/h absolute tops.

220km/h though, no way!

1. The car used possibly was Claude's Mercedes, rather than a Ferrari. This picture possibly confirms it, supposedly of Claude and the gyro-stabilised camera rig on the front of a Mercedes.

2. For the metrically-challenged, 220km/h is about 137mph, 120km/h ~= 74mph, 100km/h ~= 62mph.

Saturday October 29, 2005

Politics and the English Language

An excellent essay on Politics and the English Language written by George Orwell in 1946 which, rather sadly, is still well worth reading. Its advice ought to be kept in mind when writing anything, the essay reread frequently to keep its points fresh in mind. The translation of the verse from Ecclesiastes sums it all up very well.

He makes a point on the use of foreign words without good reason, which I agree with strongly. The fad for using german words in English, for example, annoys me a lot. Google have their "Zeitgeist", blogs talk of the "gestalt" and even IEEE papers talk about their "Gedanken" experiment. What the hell do these words mean? They are indecipherable to the english reading speaker, who must go and interrupt their reading to research these odd words. If you happen to speak any one of the Northern European germanic languages you probably can loosely recognise these words as: "Time spirit", "Form" and "Thoughts". But then you're still left wondering whether the meaning and connotations of the foreign word of phrase are consistent between the germanic language you speak and original german (if the language you speak is not modern german) and, worse, whether the english writer's usage was consistent with the original usage. Often it is not - it becomes corrupted in english to yet another meaning, defying any sense there may once have been in using the foreign word in english. To examine these three examples individually:

• "Zeitgeist":

  "Spirit of the times" would have done just as well and would have been easily understood., given the oh-so-smart googler (and they are smart) who decided to use this word obviously lacked the imagination to invent a new english phrase.

• "Gestalt":

  Who knows what this is supposed to mean. Possibly an arrangement of parts into some "form". But it apparently has been saddled through psychology with further, and more nebulous, meaning. English usage I've come across seems even more impenetrable to coherent meaning, e.g "the media gestalt": What does the author refer to and what, if anything, does the author mean to imply by it? To the media as a vague aggregate body? That the media as a whole can act almost as if it were cohesive body? The latter is probably a fair implication to take from the phrase, given the original meaning of "gestalt", but who knows whether the author intended that. Likely most english authors using this word simply are clueless and just use the word cause it seems cool, ignoring the fact their writing and readers would be better served with plain english.

• "Gedanken":

  The most pointless use of a german word in the English language goes to "Gedanken", as in "Gedanken Experiment". There is absolutely nothing which this useage adds over the plain english "thought experiment", not even brevity. The words are absolutely identical in meaning and connotation. Yet people feel compelled to use it, even in papers where the authors clearly have no need to artificially appear "smart".

If use of foreign words is clever, dan there's nearly an entire $POPULATION_WORLD out daar who are veel meer clever than we english speakers are. Obviously wij english speakers need to werk far harder at incorporating germanic and other foreign woorden into onze language. Laat ons niet be behind the zeit!

( Oct 29 2005, 03:49:24 PM IST ) Permalink Comments [1]

Friday September 02, 2005

Popular Irish women

Courtesy of Alec Muffet's blog's most recent entry, it seems Google have a rather funny notion of Irish women on their zeitgeist page.

Thursday June 09, 2005

nice project planning tool

Planner is quite a nice and useful tool. Could use some more features, but its HTML export (SWAN internal only) is very nice. Blastwave have Solaris packages of planner.

Tuesday May 31, 2005

talloc

The Samba project's talloc memory allocator is quite neat. It's a hierarchical memory allocator, so you can free arbitrary nodes in the hierarchy and have the allocator take care of freeing the node and its children. Quite neat, might steal that idea some time.

Sunday May 29, 2005

OS personality test

Yet another silly test. I remember being insanely jealous of kids who had Amigas, which wasn't really any kids I knew, cause they were so expensive, but I was able to direct my jealousy towards the imagined Amiga owning kids who I knew must have been out there :). I only had an Amstrad CPC 6128 back then, though I could at least be slightly smug with kids who only had CPC 464's, the 6128 having an extra 64k of RAM (which virtually no CPC software made use of, as the processor couldn't directly access it, it had to be bank switched with the lower 64k in some way).

Which OS are You?

Thursday May 05, 2005

double-declutching and synchromesh

Donncha,

That link you found explains double (de-)?clutching pretty well. It's required on very old cars (pre-WWII usually) and on trucks (possibly still?) which do not have synchromesh gearboxes. Synchromesh is essentially a type of clutch: as you start to engage a gear, the synchromesh engages the selected gear first via a friction cone so that by the time the dog collar on the secondary (output) shaft is fully engaged with the driven gear, the speeds of the two already match and they mate smoothly, without gearbox 'crunching'. There may be other ways to do synchromesh. DDC on down-shift is also sometimes practiced in racing, but there it's done not to get around a lack of synchromesh, but to allow quick downshifts into corners without locking the wheels due to engine braking - however the introduction of 'slipper' clutches on race machinery is removing that need now.

Without synchromesh, the driver must manually perform this task of matching the speed of the gearbox input shaft to the output shaft of the gearbox. This is done on up-shifts by pausing in neutral, with the clutch out/disengaged (otherwise the engine can't affect input shaft speed) until the engine RPM has fallen sufficiently, and then completing the shift to the next higher gear. On down-shifts by pausing momentarily in neutral, releasing/disengaging the clutch and blipping the throttle to raise the engine RPM so that the gearbox input shaft speed matches the output shaft speed and then continuing to shift down. Throttle blipping on down-shift is often complicated by the fact that you are braking and hence your right foot is on the brake pedal, so you need to 'heel-and-toe', where the ball of your foot is kept on the brake and the heel is used to blip the throttle. On some cars the throttle and brake are close enough together that you can use the side of your foot to blip the throttle, without having to twist your foot around[1]. Needless to say, driving a car which lacks synchromesh is fun :).

Note that for racing, the pause in neutral with the clutch out is not required, as in racing it's practiced primarily to avoid reverse load on the clutch and wheel-locking, rather than working around dodgy gearboxes. In which case it's simply refered to as 'heel and toe'[2].

I often drive a 1997 Mini whose synchromesh on 2nd gear has all but failed, and hence learned to double-declutch. I also double-declutch on a newer Mini, whose synchromesh is fine, but whose 2nd gear has a tendency to 'pop-out' back to neutral if the clutch is disengaged under heavy load; double-declutching helps avoid excessive load via engine-braking and hence tends to mitigate that problem. So I pretty much double-declutch all the time.

1. Particularly on race orientated cars, which, I guess, is why special 'thin' shoes are worn on race cars - the pedals are too close together to press the brake with normal shoes without pressing the throttle.

2. On motorbikes it's a trickier affair. You have to somehow keep a firm grip on the brake lever and throttle while still managing to twist the throttle. I've no idea how bike racers manage it, but judging from TV coverage they use a violent of the jerk of the elbow to get the blip while still managing to keep a hard grip on the brake lever. Thankfully, it's not needed on two stokes, which don't have any engine braking :).

[updated to be slightly less incomprehensible. Some other additions about differences between double-declutching and the racing technique of heel-and-toe]

Tuesday March 01, 2005

PC BIOSes which won't boot.

My cheap PC filer box has an annoying problem, it won't boot. It has a pair of cheap SATA cards, whose option ROMs seem to hang when called to boot the box (int 19h BIOS i think). The ROMs otherwise work fine, as GRUB from a floppy can boot fine (calling in 8xh i think, calling into the same SATA card option ROMs). It's very annoying though to have to rely on a GRUB floppy to boot.

I've been trying to think of ways to fix this, given the vendor of the cards does not appear to have released any option updates for the card to fix booting issues (the original ASIC maker apparently *did* release updates, but they don't provide downloads), and the best idea I had was to take an old NIC, old enough to have a EEPROM socket, eg the DEC DE500-BA tulip I have, and flash etherboot to it, which can be configured to boot from int80h. However I've since discovered AMIBCP, an AMIBIOS utility to allow one to customise their BIOS. Not only BIOS setup options etc, but also the various modules installed in the image, including option ROMs. I've used this to create a BIOS with etherboot and updated SATA card (recovered from BIOS update of some motherboard vendor who uses the same ASIC, using CBROM to extract modules from the Award BIOS concerned) option ROMs dropped in. Question is, am I brave enough to flash it in :). I've tested the etherboot ROM in Bochs, where it works, but prospect of a dead machine is scary.

That PC BIOSes are already modular, to a primitive extent, just not in any standard (or lasting) way, makes you wonder though how much easier life would be if only PCs had better, more modular firmware. Ah well.. ( Mar 01 2005, 07:50:58 AM GMT ) Permalink Comments [0]

Monday January 31, 2005

In unrelated news...

After a week in which at least two US army helicopters and an RAF Hercules crashed due to as yet unknown causes, Afghani authorities announced they were seeking to try persuade the population to hand in any old stinger missiles they might still have lying around.