jerichoblog

How many Asian countries can you name?

noreply@blogger.com (j.shoehorn) — Mon, 27 Aug 2007 16:13:00 +0000

Much more challenging than the 50 states quiz. If you think you know Asia, this site will really test you. Watch out for the former Soviet states and the territories of South East Asia.

read more | digg story

Name the 48 Counties of England

noreply@blogger.com (j.shoehorn) — Mon, 30 Jul 2007 14:23:00 +0000

Continuing the venerable tradition of online geography quizzes, this page tests your knowledge of the 48 Ceremonial Counties of England. As you name the counties, the names are pinned to a map of England.

read more | digg story

SIM card rejected? Phone doesn't ring?

noreply@blogger.com (j.shoehorn) — Thu, 29 Mar 2007 14:52:00 +0000

I have a very basic mobile (cell) phone, bought simply to make and receive phone calls. After a year, I started getting the message "SIM card rejected" with increasing frequency, requiring me to restart the phone. Of most concern to me was that I might be missing calls during the periods of rejection. I took the phone (a Nokia 3120) to my local Orange shop where I was told that the phone might be dying on me and that I would have to get a new one. I was not pleased!

A few more months elapsed and I found that the phone had stopped ringing, though the vibrating alert continued to work. I checked my phone settings to make sure that it was set to ring. Everything seemed to be set up OK, and the phone was still producing bleeps, suggesting that the hardware was working properly. Again, I took the phone to the Orange shop and was told I'd have to buy a new phone. Given my belief that the hardware was operational, I decided not to give up on the phone. I turned to the user manual and found how to restore the factory settings. Having done this, my problems disappeared. Note that the contacts list and text messages stay intact after the restoration. If you have a similar phone, I've copied the instructions below:

Restore factory settings
To reset some of the menu settings to their original values, press Menu, and select Settings and Restore factory settings. Key in the security code and press OK. Note that the data you have keyed in or downloaded, for example, the names and phone numbers saved in the contacts list are not deleted.

More troubleshooting information is available from Nokia.

Amateur Mathematicians

noreply@blogger.com (j.shoehorn) — Tue, 13 Feb 2007 22:18:00 +0000

Pierre de Fermat is the best known amateur mathematician, but the story of Grassman is much sadder. Something of a mathematical Van Gogh, he created the subject of linear algebra single-handedly, devised the first axiomatisation of arithmetic, and much else besides. His work was rejected by almost all professional mathematicians of the day, including Möbius and Kummer. Unlike Van Gogh, he didn't end up killing himself, but became a noted philologist instead!

Another case of a neglected mathematician is Kurt Heegner who solved Gauss' class number problem for imaginary quadratic fields (finding all nine such fields of class number 1). His proof was dismissed by the mathematical community until 1967 when Harold Stark developed a proof and showed it to be equivalent to Heegner's. Unfortunately, Heegner had died two years earlier.

How to log in to your Motorola WR850G wireless router

noreply@blogger.com (j.shoehorn) — Mon, 24 Jul 2006 18:35:00 +0000

Question

Dear Sir/Madam,

I can't access the control panel on my WR850G. I bought the unit in March and managed to set it up just fine. I enabled WPA-PSK and MAC-based authentication and disabled DHCP (as I was using another device as a router). I've had no problems with it since then, until just now when I bought a new laptop.

Naturally, I needed to access the control panel in order to enter the MAC address of my new wireless adapter. Unfortuately, nothing happens when I try accessing 192.168.10.1 on my web browser (even using the machine which can get a wireless service from the router). I get a ping response from 192.168.10.1 if I change my IP address to 192.168.10.2.

I've tried resetting the router (by holding the reset button for 30 seconds while the power is on). This seems to have no effect and the router continues to transmit the old SSID.

I've also tried running the installation utility which came with the router. This works OK until it gets to the "detecting router" stage, and then stops.

Basically, I can use the router fine as a wired switch, and I can use it as a wireless access point with exactly one wireless adapter (the one whose MAC address I'd entered into the router using the control panel). I cannot access the control panel, hence cannot add the MAC address of my new laptop.

I would very much appreciate any help you can provide me with in solving this problem.

Answer

Hello Gihan
try this hook the router to the xp computer remove the modem from the router so just 1 eithernet cable going from one of the 4 lan ports on the back of the router and the other end to the back of the pc now go to start , then click on control panell
now click on internet and network connection then click on net work connection
or you may just see network connection now right click the local area connection and go and left click properties
now high light internet protocal tcp/ip and then click on properties
now put the dot in use the following ip address Then type each of the next but subnet mask should auto populate
IP=192.168.10.4
subnet mask 255.255.255.0
default gateway=192.168.10.1
Then click on ok then close
now open up internet exploror or mozilla and in the address bar type 192.168.10.1 and see if you can get to the log in screen if you cant you will need to call the # below and talk to our tech support team there incase the router is faulty
let them know what we already did so they dont have to redo what weve already done
Thank you for chooseing motorola
If you need further assitant please respond to this email or contact us by 1877 466 8646
Thank you for choseing motorola you have a great day
Charlotte

Using Xfig with LaTeX

noreply@blogger.com (j.shoehorn) — Sun, 23 Jul 2006 16:27:00 +0000

Xfig is a program used to create drawings with lines, arcs, and splines. LaTeX is a document preparation tool. How do you use them together? I'll discuss a technique which allows you to use LaTeX strings within your figures (for mathematics, Greek text, etc). The first thing you'll need is the following entries in your LaTeX preamble:

\usepackage[dvips]{graphicx}
\usepackage{color}

The first package is essential for working with graphics in LaTeX, the second is needed because Xfig enters colouring commands into its LaTeX output (even if all the output is black). Fire up Xfig with the following options:

xfig -specialtext -latexfonts -startlatexFont default

If you don't want to do this every time, just add the following entries to your .Xresources file:

Fig.latexfonts: true
Fig.specialtext: true

Go ahead and make your figure. You can enter LaTeX strings as text, these will later be converted by LaTeX into beautiful mathematics.

When you're done with the figure, save it in the same directory as your LaTeX file, let's suppose you name the figure myfig.fig. Export the file as "Combined PS/LaTeX (both parts)". This will make two new files, myfig.pstex and myfig.pstex_t. When you need to use the file in your LaTeX document, enter something like:

\begin{figure} [ht]
\input{myfig.pstex_t}
\caption{My figure}
\label{some_label}
\end{figure}

You might not be able to see the effects in the dvi file, but you should be able to see your figure if you run dvips mytexfile.dvi to create a PostScript file.

Working with PDFLaTeX

Similar principles apply if you want to end up with a pdf. Of course one simple solution is to run ps2pdf on your ps file from the previous section, but you may end up losing some pdf-specific features, such as hyperlinks. The recommended alternative is to run pdflatex instead of LaTeX. You'll need some changes to the preamble:

\usepackage[pdftex]{graphicx,color}
\DeclareGraphicsRule{.pdftex}{pdf}{*}{}

You use Xfig much as before, but this time you export the figure to "Combined PDF/LaTeX". This will produce files myfig.pdftex and myfig.pdftex_t. The latter file replaces myfile.pstex_t in the body of your LaTeX document. When using pdflatex, make sure that your Xfig is in the correct orientation (usually portrait).

Most of the information is this post was gleaned from the Xfig website, which contains much more information on using LaTeX with Xfig.

Creating a Bootable Windows XP Setup CD

noreply@blogger.com (j.shoehorn) — Sat, 15 Jul 2006 14:23:00 +0000

There are a number of reasons why you may need such a CD:

Your copy of Windows came preinstalled, and you'd like to have a backup in case something goes wrong.
You want a 'slipstreamed' setup disk, i.e. a setup disk which will install XP Service Pack 2 as part of a full install.
You want access to the Windows Recovery Console.

I actually fall into the last category — having decided to remove Debian Linux from my computer, I also wanted to remove its boot loader, GRUB, and replace it with the Windows boot loader. Unfortunately, this can only be done using the fixmbr program which comes with the Windows Recovery Console!

If you already have a Windows Setup CD, then all you need to do is to follow the instructions given in Paul Thurrott's web site. However, if you have a preinstalled version of Windows, you may find that the contents of the Setup CD are located somewhere on your hard drive. In my case, (with an Acer TravelMate 4151LMi) the Setup files are in C:\i386. You need to follow the instructions in Bart Lagerweij's web site to create a bootable CD from the Setup files.

If you have SP2 then you'll also need to 'slipstream' the Service Pack. Unless you already have the Service Pack file, you'll need to download it from Microsoft. Instructions for downloading and slipstreaming are given as Steps 2 and 3 in Paul Thurrott's web site (you need to modify the instructions a little to work with Bart's procedure).

Remote Mathematica use for Linux / Cygwin

noreply@blogger.com (j.shoehorn) — Mon, 15 May 2006 07:30:00 +0000

Unless you can afford to shell out the long green for a Mathematica licence, you may be in the situation where you have to be physically present at a University computer in order to use it. The other possibility is to remotely log-in via ssh and the X Window system. If you choose the latter path, it is crucial that you have the appropriate fonts installed on your computer, otherwise Mathematica will present you with goobledegook instead of mathematics.

I'm assuming here that you are using Linux or Cygwin. I don't know how this works for native Windows, but would be happy for any enlightenment. As a root user, carry out the following commands:

The first step is to download the Mathematica fonts from the Mathematica web site.
Create a Mathematica subdirectory of /usr/lib/X11/fonts
Copy the downloaded files to /usr/lib/X11/fonts/Mathematica
Untar the files (with tar zxvf filename, for each downloaded file called filename).
Make sure the permissions are set correctly on the files. You may have to run chmod -R 750 /usr/lib/X11/fonts/Mathematica. Essentially, just make sure that the new font files have the same permissions and ownership as all other font files on your system.

This is where the instructions for Cygwin and Linux vary. For Cygwin, enter the following lines into your .xinitrc file as an ordinary user (the file will be in your home directory):

xset fp+ /usr/lib/X11/fonts/Mathematica/BDF
xset fp+ /usr/lib/X11/fonts/Mathematica/Type1
xset fp+ /usr/lib/X11/fonts/Mathematica/PCF
xset fp rehash

You will then have to restart X for the changes to take effect (or, if you are impatient, you can enter the above lines into your command shell for an immediate change).

Troubleshooting: You may find that the font paths are set correctly when you enter the above commands (check by typing xset q), but aren't set properly when you restart Cygwin. This is probably because you aren't starting X from the startx command, and hence .xinitrc is being bypassed. You'll have to modify a different file. If you're using the fvwm window manager, place the above commands in the .xinitrc-fvwm file instead. If you use the XWin window manager, add the lines to your .bash_profile (this is a set of commands which is run for every login shell). If you use many window managers, it may be more efficient to keep the above lines in a separate file (e.g. ~/.mathemata-fontset) and then run this file from each of the startup files.

The above technique will work with Linux too, but is somewhat non-standard. The standard approach for Linux would be to enter the font paths into your XF86Config file (or your xorg.conf file if you use xorg). Just add the following lines to the "Files" section of /etc/X11/XF86Config (or the appropriate configuration file on your system):

FontPath "/usr/lib/X11/fonts/Mathematica/BDF"
FontPath "/usr/lib/X11/fonts/Mathematica/Type1"
FontPath "/usr/lib/X11/fonts/Mathematica/PCF"

That's it!

Firefox keyboard scrolling problems?

noreply@blogger.com (j.shoehorn) — Fri, 05 May 2006 21:45:00 +0000

If you don't want to the read the whole article, I'll sum it up briefly: turn off caret browsing!

Firefox has a feature called caret browsing, which can be enabled / disabled by clicking F7 or ticking the checkbox under Tools -> Options -> Advanced -> General and "Allow text to be selected with the keyboard" (or "Always use the cursor keys to navigate within pages" for Firefox 2). This is somewhat misleading as text can be selected with the keyboard even without caret browsing. The main difference is that the keyboard navigation keys (e.g. the cursor keys, PgUp, etc.) will affect the caret rather than the page location.

In short, if you find that the keyboard navigation keys don't act as you expect them to, turn off caret browsing.

Reviews: Kernighan and Pike, The UNIX Programming Environment

noreply@blogger.com (j.shoehorn) — Sun, 09 Apr 2006 14:39:00 +0000

A real classic of its genre, this is the first book ever written on UNIX, published in 1984 and still in print today. While some of the details may have changed, the book remains relevant by expounding timeless principles of good programming practice.

The authors are true gods in the pantheon of computer science. They worked together at Bell Labs in the early days of UNIX and have since been instrumental in the development of computing. Rob Pike co-developed UTF-8 with Ken Thompson and now works at Google. Brian Kernighan[1] co-wrote The C Programming Language with Dennis Ritchie, a book widely regarded as the bible of C. Kernighan is now a professor at Princeton University.

The wit and sagacity of these men is evident in their book. Each new idea is fully reasoned out and they take delight in presenting novel solutions with the minimum of raw material. My favourite example is their 'bundle' shell script from Chapter 3. This is a 10-line program which creates self-extracting archives by using the principle of 'here documents'.

In content, the book is split into two parts. The first four chapters deal with the details of using UNIX: simple commands, the file system, interacting with the shell, pipes, redirection, and a little on awk, grep, and sed. Chapters 5 through 9 are more directly concerned with programming. In particular, shell programming is covered in Chapter 5, culminating in the development of a version control system! Chapters 6 and 7 discuss the stdio library and UNIX system calls. Chapter 8 brings it all together with the implementation of 'hoc', a programmable calculator. Kernighan and Pike take the time to develop it organically, building up hoc from a simple four-function calculator. This chapter introduces the yacc parser generator and the lex lexical analyzer generator. As a matter of historical interest, document preparation using troff is discussed in Chapter 9 — this system is used to create UNIX manual pages.

The only real drawback of this 20 year old book is that some of the examples don't work correctly, or are irrelevant. It is unlikely that you will use the 'mail' command to read your mail, or the 'ed' editor to write your documents. Running 'od -cb .' no longer prints out the contents of the directory-as-a-file. However, these are minor issues. Learning 'ed' is a good introduction to regular expressions, and you may have occassion to use 'mail' in a shell script!

If you only buy one book on the UNIX programming environment this summer, make it this one.

[1] the 'g' is silent

Internet Tools, Web2.0, and the new Community

noreply@blogger.com (j.shoehorn) — Thu, 06 Apr 2006 14:13:00 +0000

Water, water, every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink.

Samuel Taylor Coleridge - The Rime of the Ancient Mariner

Since the dawn of the Web we've struggled to find useful information from amongst the flotsam of irrelevant websites. The first torchbearers to guide us through this mess were search engines, tracing their lineage to the pre-Web Internet. The modern age has sprouted a new generation of tools and services which depend on the collaborative force of diverse users. Collectively, these advancements are being referred to as Web 2.0. Some of the more sucessful manifestations of this ideal include Wikipedia, blogs, del.icio.us, flickr, StumbleUpon, Freecyle, and Slashdot.

These sites broadly fall into two camps: (1) 'Web Finders' deliver up relevant Web pages. Examples are Google, del.icio.us, and StumbleUpon; (2) 'Web Tools' are Internet resources which provide a useful service. Examples are Wikipedia, flickr, and Slashdot. Naturally, there is a certain ambiguity. Slashdot could fall into either of the two camps.

Many of the above examples will be familiar to the majority of users. I'll illustrate Web Finders and Web Tools with two lesser-known examples from each group:

StumbleUpon

Traditional search engines suffer from one major drawback - they can only show you what you're looking for. In the words of Pablo Picasso, "Computers are useless. They can only give you answers".

We've all had the experience of being alerted to a cool website by a friend or a magazine. The type of website we never would have found by googling for 'cool website'. The point is that we all have a different notion of what is cool. There cannot be a canonical list of great sites that would suit all tastes.

Coming to our rescue is StumbleUpon. You mark the sites you like and those that you don't. Based on your personal preferences, StumbleUpon will suggest sites which like-minded Stumblers enjoy. A simple idea brilliantly executed.

Freecycle

Freecycle is a great example of a global technology acting on a local level. In a sense, it is a marketplace for free goods, bringing together people with things to give away and people in need of those items. I belong to my local freecycle group in Oxford, England. As I'm without a car, Freecycle is a great way for me to get rid of unwanted possessions! When I have material needs you can be sure that Freecycle will be my first port of call.

Conclusion

In all cases, the new breed of websites make positive use of community spirit. In our modern age of nuclear families and increasing alienation, it is as though the Web has stepped into the breach to create new communities of like-minded individuals. Each such community carves out its own slice of the Internet, adding order and cohesion where once there was chaos.

For the moment social networking is in the ascendency, but the one certain truth about the Internet is change. It is unlikely that social networking will disappear, but it will ultimately transform into something else. The leaders of tomorrow's Net will be at the helm of this change.

web 2.0
stumbleupon
freecycle
community

Thunderbird Upgrade Problems - version 1.5

noreply@blogger.com (j.shoehorn) — Wed, 05 Apr 2006 19:54:00 +0000

You may have experienced problems upgrading from Thunderbird 1.07 to version 1.5. I did! In particular, upgrading caused failure of Enigmail, and there were issues using the United Kingdom / Great Britain spell checker.

One thing to bear in mind is that you will not have to delete your old Thunderbird profile, which will save much heartache if you can't recover your profile.

If you have problems after installing Thunderbird, follow these simple steps:

Start by uninstalling Thunderbird (for Windows users this would involve the Add/Remove programs applet from the Control Panel).
Delete the main Thunderbird folder, which should be located at C:\Program Files\Mozilla Thunderbird.
Reinstall Thunderbird.

Then reinstall your extensions. If this doesn't work, rinse and repeat.

The spell checker is particularly problematic. I found that the UK dictionary wasn't included even though I chose to download the British version of Thunderbird. Moreover, the spell checker marked every word as being misspelled. You can find the appropriate dictionary from Mozilla's dictionary page. Install the file as you would for any other extension. Note that the dictionary will not appear in your list of extensions. To activate the British (or other) dictionary, go to Tools → Options → Composition → Spelling. Make sure "Enable spell as you type" is checked, then choose the dictionary you want. You may have to restart Thunderbird a few times before the dictionary begins to work properly.

Reviews: Bartle and Sherbert, Real Analysis

noreply@blogger.com (j.shoehorn) — Tue, 04 Apr 2006 13:44:00 +0000

This is a superb introductory text on real analysis. It is the recommended text for first year undergraduates at the University of Oxford and covers sequences, series, limits, continuity, differentiation, integration, and uniform convergence. There is even a short section on Lebesgue integration.

The book is rigourous yet readable, contains copious exercises and is complemented with short biographies of famous mathematicians, adding a human touch to the proceedings.

The authors eschew the more informal style of some introductory texts and prepare the students for the Definition - Lemma - Theorem technique of higher mathematics. It can be somewhat terse in places, but this has the advantage of focussing the student's mind on the essentials.

Miscellaneous Pages

noreply@blogger.com (j.shoehorn) — Tue, 04 Apr 2006 10:40:00 +0000

Random matter:

Moon at St Barnabas
Daylight Saving Time - Crime, Larks, and Energy
First Day

Mathematics Pages

noreply@blogger.com (j.shoehorn) — Tue, 04 Apr 2006 10:36:00 +0000

My mathematics posts. Also see the mathspages on my main website.

Using Xfig with LaTeX
Remote Mathematica use for Linux / Cygwin
Reviews: Bartle and Sherbert, Real Analysis
Partial Preorders
Simple Margin Adjustment in LaTeX
Elementary Wavelet Analysis

Computer Pages

noreply@blogger.com (j.shoehorn) — Tue, 04 Apr 2006 10:20:00 +0000

Recipe Pages

noreply@blogger.com (j.shoehorn) — Tue, 04 Apr 2006 10:18:00 +0000

My food posts:

English-Style American Hamburgers
Gihan's Fruity Penne With Chorizo

English-Style American Hamburgers

noreply@blogger.com (j.shoehorn) — Tue, 04 Apr 2006 10:15:00 +0000

This is my own take on a classic American dish. I substitute (English) muffins for burger buns and use real cheese instead of American cheese-substitute.

Ingredients (serves two)

250g (½ lb) lean minced beef
1 clove garlic, finely chopped
3 sticks of celery, sliced
4 slices (hand-sliced!) mature Cheddar
1 handful of chopped red onion
2 (English) muffins
salt, pepper, olive oil

Method

Gently mix the beef, olive oil (about 1 tbsp), salt, pepper, and garlic in a bowl. Divide the mixture into two balls and press into patties. As with dough making, this is a sensual delight, so enjoy the experience.

Take a skillet of generous size and line it with olive oil. Place the pan on a high heat then add the patties when the oil is hot. You will need to turn the patties once, and be aware that the insides may not be cooked even if the surface is crisp — hence you should keep cooking for about five minutes after the outside seems done.

Prepare the muffins by cutting down the middle and thinly spreading Dijon mustard. Add the cooked patties followed by layers of cheese, red onions and celery. The celery will spill over onto the plate, this provides a little decoration. Now eat with your hands.

Converting DVDs to mp3s

noreply@blogger.com (j.shoehorn) — Mon, 03 Apr 2006 11:30:00 +0000

Scenario: you have a DVD and you'd like to make an mp3 of a particular track / soundclip. The simplest solution (especially for Linux users) is to use mplayer and lame, which are freely available and open source.

Basic Ripping

Mplayer will produce a wav file from the DVD, and you can then use lame to convert the wav file to an mp3. The general mplayer command line is as follows:

mplayer $SOURCE -ao pcm -af resample=44100:0:0 -aofile $WAVFILE -vc dummy -vo null

Here $SOURCE is the recording source and $WAVFILE is the output file.
There are many ways of specifying the source. If you wished to record chapters 2 to 4 from dvd title 2, the appropriate invocation would be:

mplayer dvd://2 -chapter 2-4 -ao pcm -af resample=44100:0:0 -aofile outfile.wav -vc dummy -vo null

The final stage is conversion from the wav file to the mp3 file. You do this using lame, and the correct command is:

lame $WAVFILE $MP3FILE

where $MP3FILE is the desired mp3 file name.

Mplayer and lame are available for Windows, but there may be problems playing the later chapters in a DVD, as there seems to be a 2Gb limit imposed by the underlying software.

If you don't have Linux, it may be better to try a non-free alternative. A search through Tucows comes up with a large array of Windows tools, including "A1 DVD Audio Ripper", "AoA DVD Copy", "DVD Audio Extractor", and many others!

Advanced Ripping

The previous section should be sufficient for most purposes, but there are a few more tricks which may make the process smoother. Linux users can eliminate the need for a large intermediate wav file by using named pipes. First create the named pipe with

mkfifo $WAVFILE

You can now issue the lame command, followed by the mplayer command (preferably on different consoles). Delete the $WAVFILE file once you've finished the process.

Mplayer has a large variety of options. We've already seen how to specify the chapters you want to record. Another alternative is to specify the seek time. For example, to start recording from 1hr 30mins 40s, issue the following command:

mplayer dvd://2 -ss 01:30:40 -af resample=44100:0:0 -ao pcm -aofile outfile.wav -vc dummy -vo null

To find out more about mplayer, read the manual page.

Moon at St Barnabas

noreply@blogger.com (j.shoehorn) — Sat, 01 Apr 2006 21:55:00 +0000

Moon at St Barnabas
Originally uploaded by Gihan Marasingha.

We've spent some time looking at the Moon in Oxford. Here's a calm picture of the Moon sitting by St Barnabas church tower in Jericho, Oxford. This photograph was taken by Maggi and we can see an acacia tree in the foreground.

Daylight Saving Time - Crime, Larks, and Energy

noreply@blogger.com (j.shoehorn) — Fri, 31 Mar 2006 17:40:00 +0000

This Sunday, clocks go forward at 2:00am in most of the U.S. The biannual clock-changing has been marked by controvery since it was first conceived by Benjamin Franklin in 1784. Many late-night revelers feel cheated of an hour's drinking time. This has lead to Time Change Saturday riots in Athens Ohio, witnessing skirmishes between armed police and rowdy students.

However, the general trend is that Daylight Saving Time reduces crime. One study in Washington DC found a 10 to 13 per cent decrease in violent crime. This is due to lighter evenings, making crime more detectable.

Unfortunately, there is a downside for 'larks' — those who naturally wake early. They are genetically more aware of light and will have a harder time adjusting.

Finally, this is the last year that clocks 'spring forward' on the first Sunday of April. From 2007, the time change will occur on the second Sunday of March, with a corresponding alteration in the Fall. This is in accordance with the Energy Policy Act of 2005, which hopes to give a 1 to 2 per cent saving in household energy use by reducing the need for electric lighting in the evenings.

A Reformed Linux Zealot Speaks Out

noreply@blogger.com (j.shoehorn) — Thu, 09 Mar 2006 08:26:00 +0000

They say there's nothing worse than a reformed smoker. Perhaps that's true, but it's a great thing to be a reformed Linux Zealot. Actually, not using Linux is akin to smoking and drinking all you want and generally having a big party (note this is a simile - I don't smoke at all and drink only in moderation).

I take this opportunity to share a tale with my Linux brethren in the hopes that I may lead you to the land of Easy Computing in far off Redmond (though Cupertino works too). As you read my story, you will come across familiar horrors such as driver woes, kernel compilation, and writing scripts just to get basic functionality. I begin with a brief chronology of my computer use:

c. 1988 Sinclair ZX Spectrum 128K +2 (died in action)
c. 1992 Acorn Electron
c. 1994 PC (Western Systems 486 SX 33 MHz, 4Mb RAM, 270 Mb hard drive)
1994-2005 A succession of upgrades / cannibalisations with second hand PCs
2005 Acer Travelmate 4151LMi Laptop (Pentium M 725 @ 1.6 GHz, 512 Mb RAM, 60 Gb hard drive)

I was introduced to Linux in 1996 on university computers at Imperial College, London. Having dabbled in C programming on the Windows platform, I found Linux to be a breath of fresh air. At the time, a programmer had to use many system calls to get things done properly with Windows. All this was transparent to Linux, and it was really just a case of coding in ANSI C. Even more wonderful for a cash-strapped student was the fact that the gcc compiler is free.

At some point in my undergraduate career, I decided to go dual-boot and opted for Debian (either Slink or Potato, I forget which). In retrospect, this was a terrible choice as a first Linux distribution. At the time, Debian was very much a hardcore distribution and only for the brave souls who wanted to get down and dirty with Linux. My first installation took a couple of very stressful days, and involved a steep learning curve. A major source of stress was the worry that I would accidentally format my Windows partition, or that the resizing process would damage it somehow. These days, I would strongly recommend backing up data before messing about with partitions.

Linux was not entirely hardware-friendly. In particular, I spent many hours (days?) getting sound, joysticks, and printing to work properly. Only by recompiling the kernel was I able to get sound to work properly. Things are somewhat easier now with the introduction of kernel modules, but it's still something of a hassle.

I switched to Red Hat 6.2, and then to Pink Tie 9 (a Red Hat 9 clone). This distribution was sufficiently capable that I dropped Windows 95 in favour of it, only returning to Windows when I needed to use MS Office (which was infrequently). I saw further improvements with Debian Woody and then Debian Sarge. By the time I got to Sarge, Windows was a distant and rather unpleasant memory.

As a mathematician, my main applications are: a web-browser and email client, emacs (a text editor), LaTeX (a typesetting application), and Maple (a computer algebra package). Unencumbered by reliance on MS Office, I was entirely free to use whatever operating system I desired. Ironically, it was this very freedom which ultimately led me back to Windows.

My brand-spanking new laptop had a SATA drive. Unfortunately, this drive was not recognised by the Ubuntu Hoary Hedgehog installer (Ubuntu being my current Linux distribution of choice). Instead I installed Debian Sarge. The problem was that the system still needed considerable work to support my wireless card and didn't have xv support for my graphics card.

Back in the dual Linux/Windows 95 days, I would have had no option but to spend hours configuring the drivers, recompiling the kernel, etc. However, I suddenly found myself working with a perfectly functioning Windows XP Pro. Other than some relatively minor tweaks, XP worked fine. It was a busy time for me with deadlines fast approaching, so I ditched Sarge in favour of Windows XP. I haven't looked back.

Don't misunderstand me, I didn't drop open source software. I didn't even completely ditch Linux. Other than the operating system, the only commercial software I use is Maple (so no change from my Linux days). When I need the power of Linux, I turn to Cygwin, a Linux-like environment which sits on top of Windows. The advantage of Cygwin over a virtual machine is that Cygwin uses the Windows filesystem, device drivers, and system calls, but presents a Linux-like API to applications. In effect, it is Linux but without the hassle!

I now find that I spend much more time getting things done, instead of tweaking my Linux system to the nth degree. If Linux is to find mainstream acceptance, developers should make hardware support a priority. Ubuntu seems to be going in the right direction by offering the xorg server and generally good automatic hardware configuration. The turning point will come when major computer manufacturers produce good machines with Linux preinstalled.

The point of my article is that in these days of free/open source software, the operating system has become less important, not more. Applications are the king and they are no longer tied to particular operating systems.

Partial Preorders

noreply@blogger.com (j.shoehorn) — Sun, 05 Mar 2006 21:27:00 +0000

How many transitive and reflexive relations (partial preorders) are there on a set of three elements? This question was recently posed in a first-year maths problem sheet at the University of Oxford.

It can easily be shown that there are 64 reflexive relations on such a set, and one can determine which of them are transitive. This is a bit of a pain, so I wrote a Maple worksheet to simplify the process.

The worksheet computes all relations on a set of 3 elements and represents them as matrices. Without loss of generality, the set of 3 elements is S = {1, 2, 3}. A relation is then represented by a matrix A with entries from {0, 1}, where A[i, j]=1 iff i ~ j.

With this representation, a matrix is reflexive iff the diagonal entries are all 1. The transitivity condition is a little more complicated, but can be coded without much difficulty.

It turns out that the answer is 29.

Gihan's Fruity Penne with Chorizo

noreply@blogger.com (j.shoehorn) — Sat, 25 Feb 2006 16:55:00 +0000

Here's a delightful meal I whipped up this lunchtime. It was very scrummy, so I thought I would share it. The recipe below is for two people.

You will need:

one chorizo sausage
200g penne
two nectarines
a handful of corriander

Boil the penne according to the packet instructions. While you're doing this, slice and skin the chorizo (the slices should be about 5mm in thickness). Fry them gently in a little olive oil. Slice the nectarines and cut each slice in half. Coarsely chop the corriander.

When the penne is boiled, drain it and add to a warmed plate. Add the chorizo and drizzle the chorizo oil over the pasta. Add the sliced nectarines and corriander. Season with a little salt and pepper.

This dish is delicious with a nice herb salad consisting of baby spinach, roquette, corriander, lollo rosso, chives, and frisee. For a light dressing, just add a little olive oil, balsamic vinegar, and salt.

Simple Margin Adjustment in LaTeX

noreply@blogger.com (j.shoehorn) — Sat, 25 Feb 2006 11:01:00 +0000

LaTeX enforces beauty upon its documents, sometimes to the detriment of practicality. By default, LaTeX margins are extremely generous. This leads to good-looking documents, but there are occasions when it may be better to have smaller margins — for instance, if you want a document to fit entirely within one page.

Page layout with LaTeX is a complicated matter. A cursory glance at the LaTeX documentation shows that the layout is determined by 11 different parameters. However, I find that the following commands are sufficient for most purposes:

\addtolength{\textwidth}{ain}
\addtolength{\hoffset}{-bin}
\addtolength{\textheight}{cin}
\addtolength{\voffset}{-cin}

where a, b, c are numerical quantities such that a=2b. The effect of these commands is to increase the extent of the horizontal material by a inches and increase the extent of the vertical material by c inches.

If you want more control over your margins, then I highly recommend the LaTeX geometry package. The author of the geometry package is careful to ensure that all page settings are correctly assigned, leaving a straightforward interface to the user. As a simple example, add the following to your preamble:

\usepackage[hmargin=3cm,vmargin=3.5cm]{geometry}

This sets the left and right margins to be 3cm and the top and bottom margins to be 3.5cm. Full details are set out in section 5.3 of the geometry user manual.