Copious Free Time

Another Blair down

2008-10-02T18:54:00.001+01:00

[reading: Terry Pratchett, "Nation"; recently Greg Bear, "Darwin's Radio"]

Pirates

2008-09-19T14:47:00.001+01:00

[reading: Robert Harris, "The Ghost"; recently Warren Ellis, "Crécy", John Scalzi, "The Last Colony", Garth Ennis, "The Boys: The Name of the Game", Garth Ennis, "The Boys: Get Some"]

It's that day again.

MacBook Pro

2008-07-20T10:58:00.000+01:00

[reading: R.J. Hillhouse, "Outsourced"]

New toy: a MacBook Pro to use as my new primary machine.

I put the other blog to good use—I decided to reinstall everything from scratch, rather than use a Time Machine restore (which would have transferred a bunch of cruft, and would have meant that all the binaries would be the slower PowerPC versions rather than Intel versions). A couple of days later, I'm done.

It's definitely faster than the old machine, but I don't have a good feel for by how much. I compared the time taken to rebuild one of my current projects (90 seconds vs. 255 seconds) but that was for quite a disk-bound build process, which will limit the advantage of the new machine.

One Year On

2008-07-07T19:02:00.000+01:00

[reading: James Bennett, "Practical Django Projects"; recently Neal Asher, "Hilldiggers", Warren Ellis, "Global Frequency: Denotation Radio", Warren Ellis, "Apparat: The Singles Collection volume 1", George R. R. Martin, "A Song for Lya", Joss Whedon, "Buffy the Vampire Slayer: No Future For You"]

Previously.

He appears to like cake.

Please accept from me this unpretentious bouquet of very early-blooming typos

2008-06-17T19:50:00.000+01:00

[reading: Christopher Brookmyre, "Attack of the Unsinkable Rubber Ducks"; recently Neil Gaiman& Michael Reaves, "Interworld", Connie Willis, "Uncharted Territory", Joe Abercrombie, "Before They Are Hanged"]

A new low: this time I spotted the first problem while the initial printed draft was still en route. What's worse: it was a bug in the TeX code, rather than a typo, which means that the mistake affects 85% of the pages…

Spine: Still Evil

2008-05-25T20:27:00.000+01:00

[reading: Lois McMaster Bujold, "The Sharing Knife: Passage"; recently Joe Abercrombie, "The Blade Itself", Richard Morgan, "Black Man", Alastair Reynolds, "The Prefect"]

The spine is evil. Still.

[A:42264 B:3890 C:352 D:9325 E:96595 Total:152426]

--work-properly

2008-04-17T11:36:00.000+01:00

[reading: Jean Hugard & Frederick Braue, "The Royal Road to Card Magic (revised edition)"; recently Henning Nelms, "Magic and Showmanship: A Handbook for Conjurers"]

Today's --work-properly option: adding -rdynamic (a.k.a. --export-dynamic) to a GCC link line will mean that any dlopened libraries are able to bind to the symbols in the running executable.

Programmed Obsolescence Bug

2008-04-04T14:54:00.002+01:00

[reading: Donald Knuth, "Digital Typography"; recently Neil Gaiman, "M is for Magic"; Neil Gaiman, "Odd and the Frost Giants"; Atul Gawande, "Better: A Surgeon's Notes on Performance"]

We had a new washing machine delivered today, because my old washing machine was on its last legs—it only spins about a third of the time, although the rest of the cycle still seems to work fine.

Which is a shame, as I bought the old machine (a Zanussi FL828) in 1995. Second hand.

(And yes, I was impressed enough with it that I've bought another Zanussi).

At the Zoo

2008-03-22T11:45:00.001Z

[reading: St. Clair, John, "Project Arcade: Build Your Own Arcade Machine"]

The plus side of going to the zoo:

The slightly more disconcerting side:

But someone didn't seem that impressed (he was more interested in the neighbouring boy's sandwich):

Ken acquires restraint (for some unfathomable reason)

2008-03-17T20:32:00.001Z

[reading: Mary Gentle, "Ilario: The Lion's Eye"; recently Robert Harris, "Imperium"]

Imagine my surprise. Unlike every other year, this year's hike in the GLA part of my council tax bill is below inflation.

Year Annual Cumulative

GLA CPI RPI GLA CPI RPI

2000/2001 100.00 100.00 100.00

2001/2002 22.7% 0.9% 2.3% 122.69 100.90 102.30

2002/2003 15.2% 1.5% 1.3% 141.39 102.41 103.63

2003/2004 29.1% 1.5% 3.1% 182.47 103.95 106.84

2004/2005 7.5% 1.1% 2.6% 196.24 105.09 109.62

2005/2006 5.5% 1.9% 3.2% 207.04 107.09 113.13

2006/2007 13.3% 1.8% 2.4% 234.68 109.02 115.84

2007/2008 5.3% 3.1% 4.8% 247.10 112.40 121.40

2008/2009^† 2.0% 2.2% 4.1% 252.04 114.87 126.38

†March 2008 CPI/RPI figures not yet available; January 2008 figures used instead.

Year	Annual	Cumulative
	GLA	CPI	RPI	GLA	CPI	RPI
2000/2001				100.00	100.00	100.00
2001/2002	22.7%	0.9%	2.3%	122.69	100.90	102.30
2002/2003	15.2%	1.5%	1.3%	141.39	102.41	103.63
2003/2004	29.1%	1.5%	3.1%	182.47	103.95	106.84
2004/2005	7.5%	1.1%	2.6%	196.24	105.09	109.62
2005/2006	5.5%	1.9%	3.2%	207.04	107.09	113.13
2006/2007	13.3%	1.8%	2.4%	234.68	109.02	115.84
2007/2008	5.3%	3.1%	4.8%	247.10	112.40	121.40
2008/2009^†	2.0%	2.2%	4.1%	252.04	114.87	126.38

You'd almost think there was some kind of impending election^*.

* Which is a wonderful link, by the way. I'd pretty much given up hope of any journalist bothering to do their job, rather than just recycle press releases.

Back /home

2008-03-09T17:47:00.001Z

[reading: Iain Banks, "The Steep Approach to Garbadale"]

After a long break, I've just reinstated Linux as an OS on one of my machines.

I was tempted to go back to Slackware, which I used from 1993 to 1998 (until I was tempted away by the shininess of Red Hat), but as I keep hearing mention of Ubuntu, I thought I'd try that. (Also, it gave me a chance to run with the Debian package system instead of RPM for a change.)

The install was very smooth—smoother than any of the Windows installs I've done in the last few years (about 7 XP + 2 Vista), and just as smooth as Mac OS X (which I've done twice recently). However, the Linux install really wins big when in comes to adding in extra packages with the package manager.

On Mac OS X, getting all of the software, tools, utilities and depedencies was a fairly long-winded process (hence the blog about it, both so I could repeat the process myself if the machine died, and so that anyone else who had similar problems might be able to find useful information via the Magick of Google).

On Ubuntu, I just ran my top-level makefile; whenever some bit of build failed I just went into the package manager and installed the relevant missing package, then moved onto the next step of the build. In the end I think I only had to install three things from source, and two of those were very obscure.

So now I'm up and running fully, with access to all three of the major desktop development platforms.

Remote Reset

2008-02-25T20:44:00.001Z

[reading: Neil Gaiman, "Eternals"]

Someone at work was complaining the other week about the difficulties of testing with the OSE board. The board needs to have the reset button pressed after each test, and the problem was that the board lives in the machine room at the other end of the building.

I remembered that I had an old Lego Mindstorms set rotting in the cellar, so I decided to help out:

One of the motors had died in the meanwhile, but a contraption to press a button only needs a single motor. The software had rotted quite badly too—the old software that came with the set wouldn't work with XP, and there didn't seem to be any updates on the Lego website.

Open source to the rescue: the NQC compiler together with the Bricx IDE sorted out the 6 line program that I needed, and so remote reset was born.

hardware

Picture Sale

2008-02-10T10:02:00.000Z

[reading: Yannis Haralambous, "Fonts and Encodings"; recently Joss Whedon, "Buffy the Vampire Slayer: The Long Way Home"]

Apparently I (sort of) sold my first picture last week, which was a framed print of this one:

The details are little less impressive: I gave the picture to a charity shop after a clear out. They put it in the window for £9.99 and it was there one day, gone the next.

Back to Normality

2008-01-15T23:23:00.000Z

[reading: Richard Kaye, "The Mathematics of Logic: A Guide to Completeness Theorems and their Applications"]

So my laptop is back, and the Time Machine restore has gone smoothly (mostly), and I now realize (after a couple of weeks without the machine) just how dependent I am on it…

Genius

2008-01-05T11:11:00.000Z

Well, my laptop is now in for repair, and I've got a new iPod. After the crash, the iPod demanded to be restored from iTunes, and continued to demand this even after I'd restored it a dozen or so times (downgrading the firmware, trying on both Windows and Mac, reformatting the drive, changing the drive letter, all had no effect). So they gave me a new one.

Paranoia

2008-01-02T23:10:00.000Z

[reading: Warren Ellis, "Crooked Little Vein"]

Apparently you can never be paranoid enough. My backup system for the laptop was

one on-site external hard disk for Time Machine
one offsite backup on the new iPod.

Tonight my laptop hard drive died…while I was updating the offsite backup, taking the backup disk with it. So I hope the on-site backup is still OK….

What's For Dinner?

2007-12-25T10:18:00.000Z

[reading: Gerard Taylor, "Capoeira 100"]

Previously, previously elsewhere.

O for Oxygen, 0 for Zero

2007-12-22T17:15:00.000Z

[reading: Bjørn Lomborg, "Cool It: The Skeptical Environmentalist's Guide to Global Warming"; recently Charles Stross, "The Jennifer Morgue"]

Shocking. The reporting of science in the media has always been pretty rubbish, but the BBC News website can't even spell CO₂ correctly.

I'd let them off not doing the subscript correctly, even though it's not exactly difficult to do <sub>2</sub> or ₂ for '₂' (U+2082).

But not being able to spell "O" correctly is just impressively awful. And it's endemic.

Bubble Bath + Jacuzzi = ?

2007-11-26T21:43:00.000Z

[reading: Neal Asher, "Polity Agent"]

De Facto to De Jure

2007-11-24T11:10:00.000Z

[reading: Alastair Reynolds, "Galactic North"; recently Scott Lynch, "Red Seas Under Red Skies", Jeff Hawkins & Sandra Blakeslee, "On Intelligence"]

iPod Classic Verdict (continued)

2007-11-01T20:30:00.000Z

Now that I've upgraded my laptop, I've shifted the iPod back into Mac mode which means I can try out a couple more features.

Calendar

The calendar only seems to have a month view (which is too small; there's just a little flag to indicate the presence of an entry) and a day view (which is absurdly abbreviated—it only shows the entry titles, not any details, so if there's only a couple of appointments the screen is mostly blank). The day view also doesn't show the day of the week; this wouldn't be so much of a problem, except the whole app is very sluggish—so it's easy to over-scroll while waiting for it to respond, and then be displaying the wrong day.

Of course, I may be missing all sorts of better features, but as there's no manual (even online) how would I know?

Contacts

The contacts list is a bit more responsive that the calendar, but not by much. It also loses all of the categorization that the Mac OS X AddressBook application has, which makes things a bit more awkward.

I guess with both Calendar and Contacts it's just about functional if you're desperate to get at the relevant information and away from your main machine, but that's as far as it goes.

Disk mode

Now that I'm in Mac mode, this Just Works.

Debugger Translation

2007-10-22T22:46:00.001+01:00

After having to use three different debuggers in two days, I got around to producing a debugger translation table for future reference.

Doh

2007-10-18T20:27:00.000+01:00

[reading: Barbara Hambly, "Renfield"]

Note to self: when replacing an inner tube because of a puncture, check whether the outer tyre still has whatever caused the puncture in the first place embedded.

(Other note to self: don't buy replacement inner tubes for pram tyres from Mothercare—they're five times more expensive than the ones from a bicycle shop (or eBay), plus they take weeks to arrive.)

End of Another Era

2007-10-13T09:16:00.000+01:00

[reading: George R. R. Martin, "Armageddon Rag"; recently Christine Denniston, "The Meaning of Tango"]

End of another era: I finally got around to selling my darkroom gear. A shame in some ways—particularly with several hundred pounds worth of gear going for £30—but at least it's going to someone who will put it to use. (I offered the enlarger to a not-for-profit photography centre but they admitted that they already had four spare enlargers.)

Previously, previously.

iPod Classic Verdict (so far)

2007-10-05T19:39:00.000+01:00

[reading: Terry Pratchett, "Making Money"]

By dint of transferring many gigabytes of MP3 files from my Powerbook to my PC, I managed to get my new iPod working. Well, sort of.

Compared to my old 30GB second-generation iPod the extra new features of the latest model are:

Photo display
Video playing
Lyrics display
Cover flow
Much bigger disk

Let's take these one by one.

Photo Display

This mostly works, but doesn't seem to allow for much in the way of navigation or organization. Point iTunes at a directory and it will import all of the image files below that folder, but only the first level of subfolders gets reflected in the iPod organization. Given that I've got lots of photographs which are carefully arranged into a hierarchical set of folders, this destroys most of the organization.

There's a few other oddities. Firstly, when I select a particular picture on the iPod, sometimes I get a black screen; I have to press select again to actually see the picture. Secondly, the iPod display helpfully shows a date as you're navigating around the pictures, but this seems to be the date that the photo was transferred to the iPod, not the file date or the EXIF date. Finally, it's worth knowing that the iTunes import process creates an "iPod Photo Cache" directory under the place it imported from; for my data, this was about 15% of the size of the originals (and so is an issue if disk space is short).

So the net of all of this is that I won't be putting my photos onto the iPod (even after I get it talking to the Mac).

Video Playing

Drag an .MPG file into iTunes. Nothing happens. Drag a .WMV file into iTunes. Nothing happens. Drag a .MOV file into iTunes. Aha, it accepts it and will play it inside iTunes. Try to sync the movie to the iPod. No luck, just an error message saying the video is incompatible with the iPod. Hunt around in the manual to find out what's needed. Pause to hunt around for the manual, because the iPod didn't come with one. Eventually find out how to get iTunes to convert the video (right-click, Convert Selection for iPod). Wait a long time for it to convert. Look at the Movies tab in iTunes and realize there are now two identically named movie files, and there's no indication of which one is the original and which is the iPod-converted one. Run iPod sync and finally get a video running on the iPod.

Eventually, search the web and discover Videora.

To be fair, this is just a reflection in the small of the larger problem of video files. There are several different file formats (aka containers), but that's only the start of the problem—having different container file formats is like having different incompatible types of envelope. Inside the envelope, the contents can then be in many many different incompatible 'languages'—the codecs.
So if you've got a QuickTime format video file (file.mov), then Window Media Player certainly won't play it, but QuickTime may not play it either, depending on what codecs are installed. The only island of sanity in all of this is VLC, which has a good stab at playing almost everything. (Plus it's free-as-in-beer and free-as-in-speech.)

So I'm not convinced that using the iPod to watch videos on the move is worth the (considerable) effort involved.

Lyrics Display

I added lyrics to a song in iTunes, then synced and tried to view them on the iPod. "Lyrics detected, but unable to retrieve."

So it appears to be pointless to attempt to use the iPod to show lyrics.

Cover Flow

Shiny idea in theory; in practice it often can't keep up with even a slow scroll and just displays a placeholder for the album cover.

So I don't think I'll be using Cover Flow at all; I'll stick to plain text listings.

Much Bigger Disk

The first disappointment with buying a 160GB iPod is when you initially turn it on and it tells you that it has 150GB free. Hmm, where did the extra 10 GB go?

That's a comparatively minor disappointment compared to the discovery that turning on disk mode for an iPod in Windows does not mean that the iPod actually acts as a USB hard disk. That's right: if your iPod is set up in Windows mode, you can't read the disk on a Mac.

So the big disk's usefulness is severely limited. I can get all my MP3 files on it (unlike the old 30GB version), but I'm then left with 100GB that's of little use.

Other Impressions

When I bought my first iPod, I was impressed from the get-go. The box it came in was a feat of design; it came with a remote control, two different sort of cables, a docking station and a case.

Different kettle of herring this time around: bare bones for everything, from the packaging to the manual (er, there isn't one) to the cabling (FireWire is no longer supported or included, no docking station).

Conclusion

If you primarily want to play MP3s, the new iPod is fine. But don't be seduced by the suggestion that it does anything else.

Memory

2007-09-27T13:09:00.000+01:00

Today's disconcerting experience at work: discovering a hole in my memory.

I've spent a bunch of time over the last day or two trying to get up to speed on a subtle and complex area of networking protocols. The relevant RFCs are cryptic at best; the text covering a variety of complicated deployments is compressed to a mere couple of pages.

Eventually it occurred to me that there might be some internal company documents about the area, and I went a-hunting. A few searches later I'd found a much more helpful 30 page internal document, with detailed explanation, examples, multiple colours, diagrams, the whole works—very useful and much clearer than the standards documents.

So it was a bit of a surprise when I got to the back of the document and found the revision history page: I wrote the whole thing. It was only four years ago and I don't remember anything about it.

Denied

2007-09-25T19:50:00.000+01:00

[reading: Michael Spivak, "Calculus"]

Bugger. It turns out that the Apple rep who told me on the phone that the new iPod Classic would work with Mac OS X 10.3.9 was lying.

I don't really want to have to buy Mac OS X 10.4. I particularly don't want to have to buy 10.4 a mere month before 10.5 comes out. It's especially annoying as I spent a while cleaning up my music library and getting album art for everything in anticipation of the Arrival of the New Toy.

So I guess I've got an expensive paperweight for the next month or two (until 10.5 comes out).

Avast

2007-09-19T08:10:00.000+01:00

[reading: Vernor Vinge, "Rainbows End"; recently Neal Asher, "Africa Zero"]

It's that time again.

This Old House

2007-08-27T10:46:00.000+01:00

[reading: Neal Asher, "The Engineer Reconditioned"]

This is slightly disconcerting to look at; the price is also rather a shock.

Progress

2007-08-20T10:57:00.000+01:00

[reading: Matthew Woodring Stover, "Blade of Tyshalle"; recently John Scalzi, "The Ghost Brigades"]

Well, I'm back.

In twenty years (and ten days) I've travelled approximately 5 metres.

(Also, there's a vac student four desks away who wasn't even born when I first started…)

It Was Twenty Years Ago Today

2007-08-10T14:58:00.000+01:00

"You hear that Mr. Anderson? That is the sound of inevitability."

So it's finally time to go back to full-time paid work, which will mean even less Copious Free Time than recently. Having decided against a move to Zurich, I'll shortly be heading back to the nice place where I've worked for a large fraction of my career.

As before, a checkpoint (827 days).

Started a company with a colleague, building and selling a time-tracking software product.
Wrote a book on High-Quality Software Engineering (around 42,000 words).
Wrote around 92,000 words of another book project, which is on hold for the time being.
Wrote around 57,000 words in this blog thingy.
Had a couple of months paid work producing a Linux kernel module.
Put together two prototype web applications, using the Django framework (in Python, mostly on Mac OS X).
Various smaller personal coding projects:
- A 3D stick figure animation applet (in Java 1.0)
- A command-line sudoku solver (in C++).
- An applet to test attentional blink.
- A PalmOS version of MineSweeper.
- A test program to investigate anomalous exits in Windows.
- Resurrected some old nonlinear time series analysis code.
- Played briefly with some Cocoa coding.
Read 120 fiction and 74 nonfiction books.
Took 1660 photographs.
Holidays in Thailand (& Cambodia), Iceland, and a short break in Paris.
OCD indulgence: scanned all my old film negatives (5200 of them), scanned all of the ISBNs from my books (1860), and migrated all my source code and projects from RCS to CVS.
Sproglet.

Vampyre

2007-08-05T11:03:00.001+01:00

[reading: Avner Ash & Robert Gross, "Fearless Symmetry: Exposing the Hidden Patterns of Numbers"]

So it seems babies are isomorphic to vampires:

They survive by sucking sustenance from normal human beings.
They are awake and active during the hours of darkness.
They can't be exposed to direct sunlight.

Use the Source, Luke

2007-08-02T15:27:00.000+01:00

[reading: Susanna Clarke, "The Ladies of Grace Adieu"]

Bit of tidying up today—I added the source code for various of my trivial bits of code to the website

plus I added a link to my thesis (Homoclinic Bifurcations in Partial Differential Equations (PDF)) and put my beginner's guide to linkers under the GFDL. Not that I expect anyone to have much use for any of it, but it's there for the Magick of Google to find, just in case.

eBay

2007-07-27T10:22:00.000+01:00

[reading: Alan Cooper, Robert Reimann & David Cronin, "About Face: The Essentials of Interaction Design"]

So I'm slowly overcoming my Luddite tendencies and moving into the Century of the Fruitbat: I've just put up my first eBay auction. If it works out OK, I'll probably do some more—I don't think I'm ever likely to use my darkroom stuff again.

Best Foot Forward

2007-07-21T18:00:00.000+01:00

[reading: J.K. Rowling, "Harry Potter and the Deathly Hallows"; recently John Scalzi, "Old Man's War"]

Hold On

2007-07-12T11:58:00.001+01:00

[reading: Lois Mcmaster Bujold, "The Sharing Knife: Legacy", Rich Burlew, "Order of the Stick: Dungeon Crawlin' Fools", Rich Burlew, "Order of the Stick: Start of Darkness"]

Cool Birth Date

2007-07-07T11:24:00.000+01:00

[reading: George R.R. Martin, "Dreamsongs: A RRetrospective"; recently Matthew Woodring Stover, "Heroes Die", Warren Ellis & Ben Templesmith, "Fell: Feral City", Christopher Brookmyre, "A Tale Etched in Blood and Hard Black Pencil"]

Daniel Henry (formerly known as 'sproglet') made an appearance at 11:24am.

3.58kg (7lb 14oz in old money), all doing well.

EDD+4

2007-06-29T10:12:00.001+01:00

[reading: Christopher Brookmyre, "The Sacred Art of Stealing"]

I've finally found the answer to a question I've wondered about for six months now: which is a more accurate estimator of EDD, LMP or ultrasound scan (BPD).

Of course, the answer doesn't matter that much—things happen when they happen. But I was a bit bemused that none of the medical folk I asked knew the answer, and more bemused that most of them didn't even understand the question.

Looks like the answer is: BPD.

EDD+2

2007-06-27T09:47:00.001+01:00

[reading: R. Stephen Berry, Stuart A. Rice & John Ross, "Physical Chemistry"; recently Christopher Brookmyre, "A Big Boy Did It And Ran Away", Tanya Huff, "Smoke and Ashes", Frankie Manning & Cynthia Millman, "Frankie Manning: Ambassador of Lindy Hop", Christopher Brookmyre, "Boiling a Frog"]

Here's a quick reminder of the fallibility of the net. Given the current situation, I was thinking about the voiceover on that Guinness advert with the surfer:

He waits; that's what he does.
And I tell you what: tick followed tock followed tick followed tock followed tick…
Ahab says, 'I don't care who you are, here's to your dream.'
'Here's to you, Ahab'.
And the fat drummer hit the beat with all his heart.
Here's to waiting.

I noticed that the h2g2 entry for the advert (which is the top search result for 'tick follows tock') claims that "the voiceover comprises of passages from Moby Dick by Herman Melville".

This is simply wrong. What's more, it's trivial to confirm that it's simply wrong: the full text of the book is available^* online, and not a single line from the advert is in the book.

(To be fair, there are less prominent pages that are more accurate: "Many incorrectly attribute the text to 'Moby Dick' because of the 'Here's to you, Ahab' line", "Moby Dick-esque with a bit of Dylan Thomas".)

* Given that Melville died in 1891, even the most rabid copyright extensions haven't clawed that far back. Yet.

Bogo-Permute

2007-06-11T21:40:00.000+01:00

So here's today's random question, apropos of, er, nothing. What's the performance of the following incredibly-poor algorithm for randomly permuting a list of numbers?

def bogo_permute(in_list):
    N = len(in_list)
    out_list = []
    # Keep track of whether we have dealt with each element of the input list
    seen = [False] * N
    for iteration in range(N):
        while True:
            which = randrange(N)
            if not seen[which]:
                out_list.append(in_list[which])
                seen[which] = True
                break
    return out_list

There are N selections needed for the output list. The first time through, the randomly selected entry from the input list will definitely not have been processed already, so it can be transferred across to the output list. The second time through, there's a chance that the random selection process will select the same entry again; for later iterations, this chance of selecting something that has already been selected will get higher and higher. So, on average, how many of these repeated picks are needed?

Given a coin that comes up heads with probability p (and so tails with probability q=1-p), what's the average number of coin tosses needed before the first heads comes up?
As an example, imagine that the first head turns up on the fourth toss. This means that the sequence of tosses is TTTH. The probability of this sequence of coin tosses is then q³p = (1-p)³p. This is easy to generalize:

Number of Tosses Sequence Probability

1 H p

2 TH qp

3 TTH q²p

4 TTTH q³p

⋮ ⋮ ⋮

m T…TH q^m-1p

We want the average number of tosses needed to get a head, also known as the expected value. This is a sum of the each possible value multiplied by the probability of that value occurring. In other words, the average number of tosses needed is:

(1*(probability of heads on first toss) + 2*(probability of first heads on second toss) + 3*(probability of heads on third toss) + …)

Put into maths, this means that the average number is an infinite sum: Σ_m=1^∞ m (q^m-1p). From a trusty binomial expansion, the Σ_m=1^∞ m q^m-1 part pops out as (1-q)^-2, and since q=1-p this means that the whole thing simplifies down to just 1/p.

(This seems reasonable: for a fair coin, it takes an average of 2 throws to get a head; for a coin that only comes up heads one time in a hundred, it takes an average of a hundred throws.)

Number of Tosses	Sequence	Probability
1	H	p
2	TH	qp
3	TTH	q²p
4	TTTH	q³p
⋮	⋮	⋮
m	T…TH	q^m-1p

So back to the original problem. For the i-th selection (with i running from 1 to N), the chance of picking an array entry that is still there is p=(N+1-i)/N, and so the average number of picks needed is N/(N+1-i). The first selection needs N/N = 1 attempt, the second selection needs N/(N-1) attempts, the third selection needs N/(N-2) attempts, …, the last selection needs N/1 = N attempts (on average).

Taken together, this means that the average number of random picks for the whole process is Σ_i=1^N N/(N+1-i). Rearranging (with j=N+1-i) this is the same as N Σ_j=1^N1/j, which includes a partial sum of the harmonic series, known as a harmonic number H_N. In the large N limit, the harmonic numbers tend to H_N ≈ ln(N) + γ (where γ is a constant), and so the asymptotic behaviour of the algorithm is O(N ln(N)).

So it's bad, but not quite as bad as I'd expected (I'd guessed it would be O(N²)).

Please Hammer Don't Hurt 'Em

2007-06-10T10:50:00.001+01:00

[reading: China Miéville, "Un Lun Dun"; recently Atul Gawande, "Complications: a Surgeon's Notes on an Imperfect Science", William Carlos Williams, "Collected Poems I", Christopher Brookmyre, "Not the End of the World"]

Some unexpected good news this week: our water hammer has disappeared.

It's been a problem ever since we moved in, and apart from the annoying noise I've always been worried that eventually it would shake loose one of the pipe joints and we'd get a leak.

I'd been looking at a variety of expensive solutions for the problem, and I've already spent a day on the cheaper approach of pulling up the floorboards in order to clamp all of the pipes.

The water board to the rescue. They've been replacing the mains all round the area, and this week they came back to join up the new mains to all of the houses. It took a day or two to notice what was missing: the annoying 'thunk' whenever a tap shuts off has gone!

De-Reg-istered

2007-06-01T14:19:00.000+01:00

[reading: Christopher Brookmyre, "Country of the Blind"]

Sad news: we heard today that Reg got put down a couple of weeks ago. We hadn't seen (or heard) him for a few weeks, so we'd suspected the worst. He'd been looking pretty ill for a while, and he was around 18 or 19, so it wasn't really a surprise.

Is the Pope…?

2007-05-31T16:19:00.000+01:00

[reading: Nancy Kress, "Beggars in Spain"]

Can someone explain to me why a Catholic cardinal attacking abortion is news? After all, it's only been the Catholic position for two thousand years or so…

The Dead Pool

2007-05-25T09:42:00.001+01:00

[reading: Tracy Hogg, "Secrets of the Baby Whisperer"; recently Kurt Vonnegut, "Slaughterhouse Five", Christopher Brookmyre, "All Fun And Games Until Somebody Loses An Eye", Greg Bear, "Vitals"]

Looking at the list of dead (or dying) computer skills, I'm starting to feel old. Of the 10 on the list, I've got experience in:

Non-IP networks: Yep, about 2.5 years of SNA programming (although the last time I messed in SNA was fortunately back in 1996).
C programming: Er, over 10 years of this, although a large fraction of the recent stuff has been more of a C/C++ hybrid (which slightly misses their point—the article specifically targets pure C programmers).
OS/2: Ah, the half operating system. As Bill Gates presciently put it (in the foreword to a book that I read at the time), "I believe OS/2 is destined to be the most important operating system, and possibly program, of all time". I had probably a year or so working on it (a printer driver and a comms system) back in 1989/1990.
Cobol: Actually, no. But if they'd mentioned Fortran instead, I'd have to admit to a couple of years of it. Most recently in 2005 (don't ask).

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inline_related_objects

2007-05-04T17:01:00.000+01:00

[Edit, Feb 2008: fixed typo—changed extra_content to extra_context]

Today's neat Django trick: getting the create_update generic views for a model to display entries from a subsidiary model in-line—like the admin interface does when you add edit_inline=models.TABULAR.

The (oldforms) Form object that gets generated by the create_update view already has most of the required gubbins inside it; we just need a few extra steps to get at it:

In urls.py, set an extra_context argument for the view to be a dictionary that contains inline_related_objects:
```
 {'inline_related_objects': model._meta.get_followed_related_objects(None) } 
```

In the template, include a loop to pull in all of the related objects:

 {% for related_object in inline_related_objects %}{% edit_inline related_object %}{% endfor %}

within the <form> tag.

Since the edit_inline template tag is not a built-in Django tag, the template also needs to load up the admin_modify extension:
```
 {% load admin_modify %} 
```
Make local copies of the relevant admin templates (such as admin/edit_inline_tabular.html and widget/foreign.html) and tweak appropriately.

Of course, I didn't figure this out until after I'd spent a couple of hours dismantling the admin interface code with a view to stealing the relevant bits. Roll on the Django book.

ER Considered Harmful

2007-05-02T09:17:00.000+01:00

[reading: Enkin et al, "A Guide to Effective Care in Pregnancy and Childbirth"; recently Charles Stross, "Accelerando", Charles Stross, "Glasshouse", Douglas Hofstadter, "I Am a Strange Loop"]

Hmm. Maybe watching this episode of ER wasn't such a good idea just at the moment.

Watching old ER episodes, it's interesting to see various actors who I recognize from things they've done since. This episode had Bradley Whitford, who's much more familiar now from West Wing; continuing the theme, only 2 episodes earlier Janel Moloney (Donna) showed up—although I mostly recognized her from her voice. Likewise, the voice of Richard Brooks is very distinctive, even though he only shows up in one episode of ER and a single episode of Firefly (as Jubal Early). [Edit: also Richard Schiff, almost unrecognizable without the beard but again with a distinctive voice.]

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Geek Spam

2007-04-24T10:08:00.001+01:00

[reading: George R.R. Martin, "A Feast for Crows"]

Today's peculiar spam:

TO ALL INVESTORS!
WATCH ABC.D!!
Symbol: ABC.D
Company: xxxxx xxxx xxxxxx
5-day Target: 0.95
Current Price: 0.33 (UP 70%)
WKN: xxxxx
ISIN: USxxxxxxxxxx
Market: Frankfurt

WE ARE EXPECTING GAINS OF 
UP TO 500% IN A MATTER OF DAYS!

The TRACE statements got me to the problem and it has to do with threading. Rectangles typically are described by upper-left and lower-right corners.
I am positive that in the vast majority of cases we are hammering nails with microscopes.
You can control the compilation driver.
Normally since there is only one sound card in your system only one front panel at a time can be used for SSTV transmission or reception. The two sisters at once called on Mrs Bolton, in a newish house in a row, quite select for Tevershall.
Her thirst was gone, her aches.
Notice that a NDIS packet filter value of zero disables packet reception.
The component for which you want to find a site.
Specifies whether the type should be marshaled using the Automation Marshaler or a custom proxy and stub.
It's just impossible to include full list of them on this page.
Examples of real-world spotlights include desklamps, headlights, and flashlights. So he's been in London all this time seeing his lawyer.

Unsurprisingly, this slipped past my spam filter (particularly as the text on the left is in a GIF image). However, my question is this: for the recipients whose spam filters this is designed to get around, how many of them are likely to respond to a pump-and-dump spam email?

In other news, I'm off for my first Slacker's Lunch in ages—almost a year to the day. The plan is to go bowling, so we may stay relatively sober.

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The Joy of UNIX

2007-04-14T14:50:00.000+01:00

UNIX credo: you can do anything from a single command line (as long as the line is allowed to be arbitrarily long).

Case in point: generating a white noise audio file

sox -t sl -r 44100 -c 2 /dev/zero \
-r 44100 -c 2 -w whitenoise.wav synth 10:00 whitenoise vol 0.6 fade q 10 10:00 10

Internet 1 Banks 0

2007-04-13T19:08:00.000+01:00

[reading: Neil Gaiman, "Fragile Things"; recently Gina Ford, "The New Contented Little Baby Book"]

Maybe this Internet thingy will catch on after all.

I wanted to change my savings account to something that paid more interest, but it seems you can't just fill out a form. Instead the branch staff told me I'd have to wait until I could get an appointment next week and spend 45 minutes discussing it with a financial advisor.

So I went home and rang up to close the old account anyhow. This took more time than setting up a new savings account with an online bank—I know this because I did it during the 12 minutes I was waiting on hold.

<rant subject="banks">
I picked my existing savings account because it had their highest rate, so I was surprised that its rate had dropped low enough that I was losing money in real terms. On asking, I was told it was because it was an "old" account, and that they only have their best rates for the newer products. The rates are even worse for the older accounts that can't be opened any more.
So you can't just pick an account and assume that natural competition between the banks will keep the rates fairly close to the best of the market—you have to check every couple of years to see if your account has been superseded.
Presumably this also means that there are plenty of customers who never notice this and just trust that they're getting a fair deal. To me, that seems effectively the same as a door-to-door conman, scamming little old ladies, except it's being done wholesale rather than retail.
And another thing, while we're on the subject of dubious business practices from banks. When I looked at the comparison sites for cash ISAs, the Barclays 'Tax Beater' cash ISA stands out with a rate (6.5%) that's distinctly better than any of the competition.
However, the devil is in the details. Looking at the small print, this rate only applies for the first 12 months; the true equivalent long-term rate is 5.5%—which would put them rather further down the comparison tables.
This is a common trick, relying on customer inertia as above. But there's more: extra small print that says they don't allow any existing cash ISA funds to be transferred in—which means the higher rate will only ever apply to £3000 (at most) for one year.
So the headline rate of 6.5% that gets them to the top of the tables (and that they trumpet on their advertising) only costs them £30 per customer—which is pretty reasonable, as customer acquisition costs go. Nice scam.
</rant>

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Welcome to the Twenty-First Century

2007-04-09T14:40:00.000+01:00

This is impressively rubbish for an online shop:

Disconcerting Sight

2007-04-05T14:46:00.000+01:00

Done/Abandoned

2007-04-04T10:25:00.000+01:00

[reading: Charles Stross, "The Hidden Family"]

"If you've ever written a book, it's not really finished but abandoned." – Lemony Snicket

The second proof copy of the printed version of my witterings about software engineering arrived, and (unlike the previous proof copy) I couldn't immediately spot any egregious errors (although I'm sure there are many still lurking).

So I've finally made it visible to the world: "High-Quality Software Engineering", available as:

Web page (1.1 MB)
PDF file (83 pages, A4, 4.1 MB)
Printed book (128 pages, 6"x9", $27.95)

In theory, the Lulu distribution process means that the printed version will eventually trickle through to an Amazon listing, which would be good.

As an aside, it's been interesting to find out more about the where the money goes with book prices. It seems normal that the book seller (e.g. Amazon) gets 50% of the cover price. The other 50% covers the production cost and then what's left goes to the publisher and eventually the author. This means that the author of a reasonably popular book can make more on Amazon referrals than on royalties!

Luck

2007-03-31T11:09:00.000+01:00

[reading: Edward Tufte, "Beautiful Evidence"]

Apparently my luck is improving, judging from the emails I've been getting. In fact, I'm so lucky that I win competitions that I never even entered. The luck extends to getting advance warnings about problems with online bank accounts that I don't have.

After my previous worry about spam, things seemed to quieten down again (to ~1/week), but the levels have started to rise again more recently. Wonder why it seems to come in waves?

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Typos Uncloaked

2007-03-19T16:04:00.001Z

Normally, when you try to proof-read your own text, there's some sort of stealth field that hides all of the errors—it's very hard to spot your own mistakes. However, I've discovered that there's something different about a properly printed copy of your own stuff: suddenly mistakes just seem to leap out.

In forty-odd thousand words that I've already checked several times, I've spotted:

9 erroneous wordings
10 instances of errant punctuation
5 layout errors
4 formatting/display tweaks
1 bug
2 inconsistent spellings
10 infelicitous wordings.

And of course this is unlikely to be everything.

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Thanks, Ken

2007-03-17T10:51:00.000Z

[reading: "The Sagas of the Icelanders"]

I've just had my council tax bill for the year, and once again the part of the council tax bill that goes to the Greater London Authority (GLA) has risen faster than inflation. This triggered me to do a little rummaging in my files, to look back at the GLA part of my council tax bills.

Year Annual Cumulative

GLA CPI RPI GLA CPI RPI

2000/2001 100.00 100.00 100.00

2001/2002 22.7% 0.9% 2.3% 122.69 100.90 102.30

2002/2003 15.2% 1.5% 1.3% 141.39 102.41 103.63

2003/2004 29.1% 1.5% 3.1% 182.47 103.95 106.84

2004/2005 7.5% 1.1% 2.6% 196.24 105.09 109.62

2005/2006 5.5% 1.9% 3.2% 207.04 107.09 113.13

2006/2007 13.3% 1.8% 2.4% 234.68 109.02 115.84

2007/2008^† 5.3% 2.7% 4.2% 247.10 111.96 120.71

†March 2007 CPI/RPI figures not yet available; January 2007 figures used instead.

Year	Annual	Cumulative
	GLA	CPI	RPI	GLA	CPI	RPI
2000/2001				100.00	100.00	100.00
2001/2002	22.7%	0.9%	2.3%	122.69	100.90	102.30
2002/2003	15.2%	1.5%	1.3%	141.39	102.41	103.63
2003/2004	29.1%	1.5%	3.1%	182.47	103.95	106.84
2004/2005	7.5%	1.1%	2.6%	196.24	105.09	109.62
2005/2006	5.5%	1.9%	3.2%	207.04	107.09	113.13
2006/2007	13.3%	1.8%	2.4%	234.68	109.02	115.84
2007/2008^†	5.3%	2.7%	4.2%	247.10	111.96	120.71

So in seven years Ken has managed to more than double his part of the London tax burden (in real terms). Still, at least he's now committed not to increase the liability of London taxpayers for the 2013 Olympics^* any more.

*Not a typo.

Magic Number

2007-03-16T15:35:00.000Z

And the number is: 978-1-84753-300-5.

Clang!

2007-03-14T20:25:00.000Z

[reading: Wesley Chun, "Core Python Programming"]

Is your life so exciting
you have to tell everyone you meet.
Try and make it so enticing;
wear your soul out to your feet.

An amusing exchange at fencing this evening, along the lines of:

Annoying new chap: "Presiding epee is more difficult than presiding foil."

Me: "Nonsense—foil has right-of-way to worry about and épée doesn't have any rules."

ANC: "No, presiding epee is more difficult than foil. Or maybe it just seems that way because I'm an international foil referee."

Impressive—he managed to work in that piece of information in his first five minutes at the club.

[Edit: And he's repeated the manoeuvre in the first five minutes of every subsequent conversation I (or anyone else) have had with him…]

(And yes, I'm assuming that he's the sort of person who wouldn't know where the accents go.)

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Proof of the Pudding

2007-03-13T09:00:00.000Z

[reading: Robert B. Cialdini, "Influence: The Psychology of Persuasion"; recently: Simon Selmon, "Swing Dancing", Norma Miller, "Swingin' At The Savoy"]

Aha! The first printed copy of my scribblings on software engineering has just arrived (somewhat later than expected, given that I put the order in nearly two weeks ago). Fortunately, the print quality seems just fine with this one (unlike my experiment with photographic content).

Of course, on the very first page that I checked any of the text, I immediately spotted a typo.

(Still, this is supposed to be a proof copy and so finding such things is the main raison d'être—one fewer in the final version.)

You know when you've been Djangoed

2007-03-01T17:31:00.000Z

[reading: Manly Banister, "The Craft of Bookbinding"]

Well, that was surprisingly straightforward—I got my first live Django site up and running inside a morning. There were a bunch of configuration tweaks, and I had to fix a couple of problems in the code that hadn't shown up under the test server, but then it was up and running. The hosting provider (WebFaction) was pretty impressive: fast, cheap and well documented. If I'd realized it was this easy I'd have gotten the live site up weeks ago.

So as that didn't take as long as expected, this afternoon I've written my first noddy AJAX code as an encore.

The Spine is Evil

2007-02-25T18:00:00.000Z

[reading: Skippy Blair, "Disco to Tango and Back"; recently: Simon Lovell, "How To Cheat At Everything"]

Drat; forgot to add extra space on the inside margins of my current typesetting project, so I had to go back through all of the chapters and re-set everything. Like the man said, the spine is evil.

Montmartre

2007-02-15T15:27:00.000Z

[reading: Scott Lynch, "The Lies of Locke Lamora"]

Also, a frustrating visit to the Pompidou centre. This involved:

queueing at level 0 to have our bags checked and get in
a couple of minutes trying to figure out where to get tickets
buying a combined "museum + exhibitions" ticket
going up to level 1 to get into the museum, only to be told my bag was too big
back to level 0 to deposit my bag at the cloakroom
back to level 1 to get into the museum
up the escalator to level 5 for the first half of the permanent collection
looking at modern art, also known as 'doodling' or 'rubbish'
discovering the second half (level 4) of the permanent collection was closed
looking for signs to the temporary exhibitions, but not finding any
going back down the escalator to level 1
…to discover a sign indicating that temporary exhibitions were on level 6
reascending the escalator to level 6
…to discover that both temporary exhibition halls were shut
redescending to level 1
going back down to level 0 to retrieve my bag
leaving.

All to be reminded that I don't really like modern art.

Louvre

2007-02-14T15:25:00.000Z

[reading: Karl Schroeder, "Lady of Mazes"]

Unexpected bonus from the French tendency towards strikes: the ticket collectors at the Louvre were on strike, so entry was free.

Museums on a non-Monday

2007-02-13T15:25:00.000Z

La Defense

2007-02-12T15:24:00.000Z

[reading: Charles Sheffield, "Between the Strokes of Night"]

We also went to the Musée D'Orsay, but it was shut on account of being a Monday. So we walked on to the Musée Rodin…which was also shut on account of being a Monday. The Eiffel Tower was still there on a Monday though.

Le Métro

2007-02-11T15:23:00.000Z

I'd forgotten how wonderful the Paris Métro is—cheap, clean, quiet and efficient. The pricing is particularly nice: a single cash ticket for a central journey is €1.40 (around £1), compared to £4 in London.

Of course, it's heavily subsidised: for every euro I spend, the French taxpayer coughs up another two euros. Which practically makes it my patriotic duty to take the Métro everywhere.

Scanned Scan 2: The Return

2007-02-07T11:21:00.000Z

[reading: Ben Willmore, "Adobe Photoshop CS2 Technique"]

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Blah blah blah

2007-02-03T18:04:00.000Z

[reading: Kingsley Amis, "Lucky Jim", Adobe Creative Team, "Adobe InDesign CS2: Classroom in a Book"; recently: Adobe Creative Team, "Adobe Illustrator CS2: Classroom in a Book", Alan Moore, "Promethea Books 1 2 3 4 5"]

I came across a really useful observation in Steve Krug's "Don't Make Me Think^*" the other day:

Happy talk must die. If you're not sure whether something is happy talk, there's one sure-fire test: If you listen very closely while you're reading it, you can actually hear a tiny voice in the back of your head saying, 'Blah blah blah blah blah….'

What's more worrying is when you get that same tiny voice repeating "blah blah blah" when you're writing.

*Excellent book, BTW; up there with Joel's UI book for accuracy, humour and pithiness.

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Disappointing

2007-01-27T13:41:00.000Z

[reading: Ty Fischer, "Color Blind"]

For one of the projects I've been playing with recently, I've been thinking it would be good to get a printed version done. The biggest print-on-demand site seems to be Lulu, so a couple of weeks ago I ordered one of their books at random to see what the printing quality was like. My project is going to involve a bunch of black and white photographs, so I picked the cheapest B&W photo book I could find in their listings.

The book arrived this morning, and the quality is very disappointing. The photographs look a bit like newspaper pictures did 20 years ago, with not-dissimilar paper quality. It's definitely down to the halftoning of the printing too—the original photographs online look fine. It seems other folk have similar concerns; rumour has it that their colour printing gives better results, but it's three times the price and seems unnecessary given that everything I'll want to print is monochrome.

So does anyone know of a print-on-demand place that gives decent results with monochrome images?

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Extras

2007-01-26T17:56:00.000Z

[reading: Douglas van Duyne et al, "The Design of Sites (2nd edn)"; recently: Steve Krug, "Don't Make Me Think"]

It's been a while since I last tried to book tickets for live music, and I'd forgotten how extraordinarily annoying the added extras are. I was thinking about going to a Tom McCrae gig, and the tickets are listed as £15.

Of course, it's naïve to think you can actually buy a ticket for that price—there's the £1.50 "booking fee" to pay too. (What exactly does that pay for? The tricky business of keeping track of what tickets are left? Given that it's a standing-only venue, that involves … counting up to 500.)

OK, so the £15 tickets are really £16.50 tickets. I'm annoyed but I can just about cope with that, until I get to the checkout and discover the additional £2 "transaction fee". (Presumably this is to pay for the back-end credit card processing, but I've looked into how much this sort of thing costs, and 5.7% (assuming people normally buy 2 tickets) is ridiculously high.)

So listing the tickets as £15 is a flat lie; they're actually £17.50 tickets.

(In the past, I've tried physically turning up at the venue to buy the tickets with cash in an attempt to avoid the fees, but it didn't make any difference—they still added on all the extras. They don't call themselves "Mean Fiddler" for nothing.)

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Continuing the theme

2007-01-23T17:52:00.000Z

[reading: David MacDonald, "The Encyclopedia of Mammals"]

I got rid of an old camera today (by donating it to the nice folk where I did a studio lighting course), which reflects a grudging acceptance of the new era—my primary camera gear is now entirely digital. In some ways I'll miss the physical experience of the darkroom, but on the other hand the efficiency gains are just too enormous to ignore—a ten-second tweak in the Photoshop Levels dialog equates to twenty minutes of producing test strip prints.

I still have a medium format camera that I use occasionally, but even with that I'm unlikely to do any darkroom work—a scan of a 6x6 negative gives a monster-megapixel image I can play with in Photoshop.

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Envy

2007-01-22T18:39:00.001Z

[reading: Peter Hopkirk, "The Great Game"]

I heard today that someone I know might be getting a new job, working as a part-time photographer for a web retailer. For some reason I'm slightly envious….

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Error in Server Configuration

2007-01-17T21:42:00.001Z

[reading: Tanya Huff, "Blood Bank"; recently: China Miéville, "Looking for Jake and Other Stories", Neal Asher, "The Parasite"]

Worrying—Thunderbird is currently reporting "Sending of password did not succeed. Mail server responded: error in server configuration". Not sure what this means about my current email connectivity.

[Edit: seems to be back to normal now.]

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Absent-minded

2007-01-13T17:37:00.000Z

[reading: Phil Wilson, "The Definitive Guide to Windows Installer"]

Hmm. Not having the most competent of days—I managed to buy a computer game that I already owned and also to leave behind something I'd bought at the supermarket, both within the space of a couple of hours.

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Bright Idea

2007-01-07T16:46:00.000Z

What a surprise. It turns out that IKEA use different lightbulb fittings than everywhere else in the UK.

It does induce a potential business idea though: surely it would be possible to make adaptors that fit into IKEA lamps and take UK-standard bayonet fitting light bulbs? You could set up a van in the IKEA carpark selling them to customers leaving the shop; a sales pitch along the lines of "Buy one of these or else you'll have to come back here again" ought to work nicely.

(It's not an entirely dissimilar business plan to the estate-car taxi services that operate outside IKEA, mopping up the customers who discover the limitations of the IKEA "delivery" service.)

SVG

2007-01-06T16:31:00.000Z

[reading: Kurt Cagle, "SVG Programming: The Graphical Web"]

I've started investigating SVG, and it's beginning to look like I chose the wrong book to read. In the source code download, the second file from the book is corrupted; the author's website has gone so there's no chance of finding fixed versions, and the Apress site for the book doesn't have any errata listed (despite the fact that the book has been out for five years and I've spotted 3 typos in the first 40 pages).

Still, at least it was cheap.

End of Another Era

2007-01-04T19:39:00.000Z

[reading: Justina Robson, "Natural History"; recently Anne Deans, "Your Pregnancy Bible"]

For one reason or another, I've sold my motorcycle.

It's a bit of a wrench: I've had a bike since December 1992, but now I'm reduced to the vagaries of London Transport. Which may not be the best of timings (well, mebbe not).

(Previously.)

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Splendid Box

2006-12-25T09:51:00.000Z

Also: good pie.

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Draft 3

2006-12-23T17:43:00.000Z

[reading: Tanya Huff, "Smoke and Mirrors"]

Finally got around to taking another pass over my scribblings on software engineering. It's been a fair while since I last looked at it—around eight months—which means I've now got enough distance to be able to spot (some of) my own typos.

I'm also finding that I rather like it as I re-read it, which is a slight surprise (almost no-one else that I've shown it to seems to have been able to wade through it, which augured badly). I've got a couple more small sections I'd like to add, but I think it's in fairly decent shape.

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Scanned Scan

2006-12-14T13:15:00.000Z

I've seen ultrasound scans before, and I could never quite understand the enthusiasm with which they were presented. They always seemed like a grainy collection of vague blobs to me, and so I thought the enthusiasm was just early-onset baby obsession.

Now that I've seen the scan in action, it makes a lot more sense. Any individual still image is grainy and vague, but as the 'camera' moves around you build up a 3D image in your head which is much more impressive. It's like being in a really dark room with a single lightbulb swinging far overhead, so that the shadows gradually converge into shapes. (Actually, that makes me think of Doom 3, which probably isn't the best association).

Django Su

2006-12-13T17:29:00.000Z

It's always a sign of good design when adding a new feature turns out to be easy.

In the Django authentication system, I wanted a way for an administrator to view the site as if they were a particular user; effectively an equivalent to su in UNIX-land.

The first easy step was to invent a URL to correspond to this action, which gets encoded in urls.py:

  (r'^su/(?P<username>.*)/$', 'qlockweb.accounts.views.su', {'redirect_url': '/qlockdata/'}),

That done, the second and final step is to write some view code.

  @user_passes_test(lambda u: u.is_staff)
  def su(request, username, redirect_url='/'):
      su_user = get_object_or_404(User, username=username)
      if su_user.is_active:
          request.session[SESSION_KEY] = su_user.id
      return HttpResponseRedirect(redirect_url)

Seven lines of code and we're done (modulo a bunch of import statements).

Expanding what's going on here:

(r'^su/(?P<username>.*)/$', 'qlockweb.accounts.views.su', {'redirect_url': '/qlockdata/'}),

When an HTTP request arrives at the framework, Django goes through its list of URLs until it finds a match. In this case, going to http://mysite/accounts/su/fred/ ends hitting the urls.py line above; the /(?P<username>.*)/ part of the regexp pulls out "fred" and this gets passed as a parameter named username into the function su in qlockweb/accounts/views.py. This function also gets passed a parameter called redirect_url with value '/qlockdata/'.

@user_passes_test(lambda u: u.is_staff)

Actually, we need to rewind one step before we get into the su function. The line before the function definition is a Python decorator: some extra code wrapping the function that gets executed just before the function itself is executed. This decorator needs some expansion of its own:
- The @ sign is the syntactic sugar that indicates that this line is a decorator for the function that comes immediately afterwards.
- This is the decorator function (from contrib/auth/decorators.py); its first argument test_func is a function that does the test. This test function is given a single parameter: the current User. If the test function returns true, the wrapped view code is called; if not, then the user gets redirected to a login page.
- More syntactic sugar. We want a function is_this_a_staff_user(u) that checks whether its argument u is an administrator. However, as this is the only place that the function is used, we don't bother to give it a name—we just use a lambda expression to give the definition right here and now.
- Finally, the body of the lambda expression just uses the method of the User class that indicates whether the user is an administrator or not.

def su(request, username, redirect_url='/'):

So now we're in the su function itself, and if we've got this far we're guaranteed that the person viewing the page is logged in as an is_staff user. The function has the username and redirect_url parameters mentioned earlier; it also has a request parameter that holds all of the information about the original web request (in a HttpRequest object).

  su_user = get_object_or_404(User, username=username)

The next line of code gets a User object for the username that was specified—fred in other words. If there isn't a user called fred, then a Http404 exception gets raised, which will percolate up the stack and display a (surprise, surprise) 404 page.

  if su_user.is_active:

This particular version of our code only allows impersonation of active users, helpfully provided by the is_active field in the standard User model.

    request.session[SESSION_KEY] = su_user.id

The next line of code is the one that actually does the work. The requesting user's session is modified so that its user ID is the impersonated user's.

  return HttpResponseRedirect(redirect_url)

The final line of code redirects the web browser off to the redirect_url page.

(Statutory disclaimer: I am not a security expert, nor do I play one on TV. Adding this to a production system is probably not a good idea.)

Another Django snippet: I finally discovered that the follow argument to the standard Manipulators allows you to list fields in the model that the form should leave untouched. Very helpful: the end result is more compact and less brittle than the code I'd put together to manually override all of the hidden fields.

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Mind Hack #39

2006-12-02T14:32:00.000Z

[reading: Jón Árnason, Alan Boucher (translator), "Icelandic Folk Tales"]

One of the MindHacks that doesn't include an easy demonstration is Hack 39, where you're less likely to notice a trigger event if it occurs soon (say, <0.5s) after another trigger event.

(Now that I've got into the content rather than being distracted by the typesetting, the book is turning out to be rather good.)

My first attempt to test this out is below, but I have to say that the effect didn't seem all that strong to me—so maybe there's a bug or I've implemented it wrong. Or maybe I'm just too impatient to run it for long enough to get statistically significant data.

After hitting "Go", this applet will display letters for a tenth of a second each. You should hit a key whenever the letter displayed is either "X" or is displayed in white. To stop the applet, hit "Stop" or press the Escape key.

After running the applet, the bar graph shows the time between triggers (on the X axis) against how many triggers there were with that delay; the white is the total number shown, the black is the subset of them that were missed. Hitting "Go" again accumulates more data.
(Download source code)

Technical Details: letters are picked uniformly (so there's a 1/26 chance of a letter X trigger) and white is used for the colour 1/20 of the time. A trigger is considered hit if there's a keypress within 1 second after the trigger, but each keypress only counts once (so "trigger, trigger, keypress, letters…" would count as one hit then one missed trigger, with a delay of 1).

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knolp

2006-11-30T14:19:00.000Z

[reading: William Faulkner, "As I Lay Dying"; recently Neil Strauss & Bernard Chang, "How To Make Money Like a Porn Star"]

Now that I've got Django installed and running, I've been setting up my first web application with it.

I spent a bunch of time yesterday trying to figure out how to get extra parameters passed through a generic view; in the end I had to UTSL to get a method that worked.

So of course today I find a nice page that concisely and coherently explains it, rather more quickly than the couple of hours it took me to figure out.

Perhaps I can suggest *knolp* (the reverse of *plonk*) as the sound of an RSS feed hitting my aggregator. (It looks like I'm not the first person to think of this.)

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&numl;

2006-11-25T20:57:00.000Z

[reading: Derek Young, "Rock'n'Roll Dancing"]

Here's a question: is there a Unicode character for an N with an umlaut?

(Triggered by eating a splendid dessert of Gü brownies and Häagen-Dazs ice cream, which made me think of that most famous of fake umlauts, the one in the name of "Spinal Tap").

Oh, and compounds like U+006E U+0208 (i.e. 0x6e 0xcc 0x88 in UTF-8) don't count.

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Editing Hacks

2006-11-21T09:59:00.000Z

[reading: Tom Stafford & Matt Webb, "Mind Hacks"]

Started reading "Mind Hacks", which looked interesting in the bookshop but the formatting is already starting to annoy me. In that respect, it's the worst book-that's-just-a-printout-of-a-cool-website ever, and that's up against some pretty stiff competition.

A large fraction of the hacks refer the reader off to movie files or Flash animations on the web. Not very helpful for a physical book that you might want to read on a train.
"Color: The second color is used to indicate a cross-reference within the text". Except that there is no second color—the relevant parts just come out in a hard-to-read light gray.
The halftoning for photographs and some of the diagrams is poor—it looks like the output of an 1980's laserprinter.
I don't know what system they used to produce the book, but it's generated some real oddities in linebreaking (mostly around URLs). Favourite so far: a line break after the decimal point in "3.3" (page 144).

Still, the content might be OK once I get into it, and at least they include lots of references to the original literature.

[25-Nov-06] Edited to clarify that I'm complaining about the formatting rather than the content. Feeling slightly guilty given that one of the authors came over and commented. You'd think I'd have learnt my lesson about who finds what on tha intarweb.

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Spam

2006-11-20T09:58:00.000Z

[reading: Martin Amis, "The Rachel Papers"]

Grr. The spammers seem to have found me. I've been using my current email address for three years now, and I've not had any spam at all until the last week or two. (There's occasional spam to webmaster@ or info@, but they're easy to ignore). I guess I must have gotten complacent and signed up to something dubious with my real address. Drat.

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One Year In

2006-11-09T15:53:00.000Z

[reading: Seamus Heaney, "North"]

Just noticed: it's a year since the original idea for the company.

Strike One

2006-11-07T10:16:00.000Z

[reading: Lois McMaster Bujold, "The Sharing Knife: Beguilement"]

One down, two to go. Still, at least it was a swift response; strike while the iron is hot for the next scary email….

Post Hoc

2006-11-06T22:09:00.000Z

[reading: Seamus Heaney, "Beowulf"]

I know it's entirely back-to-front, but I keep encountering things in Beowulf that feel like they were stolen from Tolkien: there's a minor character called Eomer, and I've just read the bit where a drowsing dragon is raised to wrath^* because a thief has snuck in and stolen a cup from his hoard. I had a similar experience in Iceland—I kept on spotting businesses apparently named after dwarves: "Balin Shipping" and "Thorin Warehouse" (or þorin) and so on.

In other news, I finally succumbed to nagging and sent off a scary email….

* Anglo-saxon alliteration is irresistibly infectious.

Scarecat

2006-11-01T08:50:00.000Z

[reading: Scott McCloud, "Making Comics"]

Over the last few weeks we've had our flat roof re-felted. (This involved an unexpected amount of hassle, as we seemed to end up in the middle of a dispute between management and workers. The dispute was nominally about health & safety, but I suspect it was really about something else—probably money.)

The trigger for getting the work done was how much it had been raining…indoors, particularly around the skylight. A quick examination revealed the primary problem: there were large, ragged, holes torn in the flashing around the skylight. The flashing was silvery, so the most likely explanation for the holes was that they had been pecked out by birds.

So when I heard a loud tapping sound this morning and looked up to see two crows attacking the newly-repaired skylight, it was time to do something about it.

* And yes, I know that "scarecat" isn't a logical variant of "scarecrow" in this context.

Astroturf

2006-10-31T11:00:00.000Z

[reading: Tom DeMarco & Timothy Lister "Peopleware: Productive Projects and Teams"]

On the plus side, this is an absolutely fascinating advert:

On the minus side, when I emailed^* Dove to see if there was a higher-resolution, downloadable copy anywhere (for a teacher friend who wanted to use it as the basis for a school assembly), I got a swift response of:

Due to licensing reasons we are unable to send the Dove Evolution Film to other organizations. We invite you to log on to http://www.campaignforrealbeauty.com/ to play the film live.

I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a response.

*When I say "email", obviously I mean "fill out a ridiculous web form that requires me to fill in my postal address". And when I say "my postal address", obviously I mean a random invented address because a) I don't want junk mail for the rest of my days and b) the address form doesn't allow non-US addresses.

Top Tip

2006-10-29T13:13:00.000Z

[reading: Alistair Reynolds, "Pushing Ice"; recently Neal Asher, "The Voyage of the Sable Keech", Steven Brust, "Dzur", John M. Ford, "The Dragon Waiting", Scott McCloud, "Understanding Comics"]

Today is my third attempt to fill the cracks in the grouting around the bathroom tiles. I have high hopes that this iteration might actually work, for I have encountered a Top Tip: fill the bath with water while the grout is drying, so that the gaps are stretched to their biggest during the drying period.

I did wonder why the cracks seemed to appear and disappear at random; I now realize that it depended on whether I was checking on them when I was sitting in the bath, or when I was standing by the bath. Doh.

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Mugging Shock

2006-10-09T22:55:00.000+01:00

Bit of excitement this evening; I was reading a bit before bed (about instruction pipelining on the PowerPC 970FX, as it happens) when I heard someone shouting for help outside. This was different from the normal young-drunk-giggly-female shouting we sometimes hear (being close to a pub)—this was an older male voice that sounded in genuine trouble.

So I trundled out to discover that it was indeed someone with trouble—a chap who'd just been mugged, around the corner. After I'd retrieved a torch and an ice pack for him from the house, I ended up tagging along with him and a policeman as we wandered down the nearby alleyway looking for the muggers and to see if they'd abandoned his bag (they had).

From his description of events: he was walking down the alleyway towards three youths coming the other way, and he had advance warning that something was up because they didn't move apart to let him pass. They hit him a couple of times, then started demanding his stuff. He handed over his bag (knowing it had nothing of value in it), and his watch when they demanded it, and was in the process of handing over his mobile phone when they started after his wallet. This triggered him to start resisting, and he grabbed back his phone and ended up keeping his wallet—but ended up being hit more (net result: a nasty looking swelling above his right eye, but fortunately no loosened teeth) before they scarpered.

It was interesting to observe someone who presumably had a touch of shock: he was fairly calm and coherent, but he kept talking continuously and repeated almost everything he said several times. He insisted he didn't need anyone to look at his eye, but I wasn't so sure myself (hence the icepack); I guess I was probably overly worried—I got one of the policemen to take a look at it (assuming he's probably got vastly more experience with black eyes than I do) and he didn't seem too concerned.

So overall he didn't come off too badly: he lost his watch, but kept his wallet, phone, briefcase and all of his teeth. Still, a bit disturbing to have a mugging 100 yards from my house….

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Scratched

2006-10-06T12:17:00.000+01:00

[reading: Amit Singh, "Mac OS X Internals"]

So I finally gave in and scratched my itch about the 5¼" floppy, by sending it away to a data recovery place. It was a little bit expensive (although still considerably cheaper than calling out a plumber) and time-consuming (two weeks, five phone calls and an email later), but worth it just for the satisfaction of never having to think about it ever again.

Amazingly, my very first TeX files (from 1989) still produce exactly the same page layouts in the TeX system on my 2005 laptop.

Learning TeX was actually driven by embarrassment. When I originally wrote the essay, it was in WordStar. Dealing with accented characters was a bit annoying in WordStar, so I decided to deal with it in batch mode. While I was writing the essay, I used 'Godel' instead of 'Gödel' all the way through. Then, just before submitting it, I ran a search-and-replace to change all instances of 'Godel' to 'Godël'.

Oops.

So when someone eventually pointed it out to me, I persuaded the college to let me have the submitted hardcopy of the essay back with the excuse that I was going to replace it with a better-typeset version—and hence my introduction to TeX.

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In Extremis

2006-09-30T17:06:00.000+01:00

[reading: Lenny Smith, "Chaos: a Very Short Introduction"; recently Terry Pratchett, "Wintersmith"]

Last Globe trip for the season, for another modern play. It's not as brutal as Titus—a piffling single mutilation and no murders (although there is some, er, hot nun-on-nun action)—but it does have some rather good theological sparring.

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The Hot Seat

2006-09-24T14:46:00.000+01:00

I'd not noticed before, but it seems that the parking meters around Haringey are at least partially solar powered. A neat idea, and I'm not the only one who thinks so:

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Smugness

2006-09-23T17:11:00.000+01:00

Kewl. Just had my tax assessment back, and even with my earlier monster tax refund, they still owe me more money.

(Not that this was really a surprise, as I'd already figured out what they would owe me. But on previous history, it was slightly a surprise that they got the numbers right—more often that not, I have to ring them up to get them to correct it).

[Edit: Also, I guess this explains why my bank balance was mysteriously much higher than I expected last week…]

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Avast, ye noodly appendage

2006-09-19T08:36:00.000+01:00

[reading: Bobby Henderson, "The Gospel of the Flying Spaghetti Monster"]

Another day closer to the worms. Still, as I've mentioned before, at least it's a particularly special day.

Reg Ringtone

2006-09-07T08:18:00.000+01:00

Some people are of the opinion that Reg, the the cat who doesn't live here, could generate a good ringtone. Even though he's incredibly loud, he seemed to view microphones with suspicion (when he's not trying to eat them) and so the samples are quieter than they should be.

Believe it or not, this isn't the sound of a cat in any sort of pain or distress—except for the distress of having to wait thirty seconds for his sixth meal of the day (provided by four different neighbours). It's a sound that was once described as "someone torturing a granny to death".

If you build it, they will come

2006-09-06T16:17:00.000+01:00

[reading: Tom Reynolds, "Blood, Sweat and Tea"]

W00t, we have customers!

Well, except for the paying money bit, obviously. We haven't actually set up a way for people to pay us money yet (which might be a bit of an oversight).

But we shifted our website around last week so that random members of the public could actually get to the beta download page and get an evaluation copy of the product, and today a couple of people found and followed the relevant links.

Reykjavík to London

2006-08-27T22:45:00.000+01:00

[reading: Alfred Bester, "The Stars My Destination"]

Just time in the morning to go back to Hallgrímskirkja

Then off to the airport and back to London.