Parallels screws up Windows

Since Parallels 3 has come out there have been a lot of complaints that it can screw up your Windows XP installation, resulting in an error like:

/system32/ntoskrnl.exe file is missing

Parallels has finally posted a fix:
http://kb.parallels.com/entry/30/516/

However, it doesn't tell you how to get your Parallels VM to boot from the Windows CD in the first place. The trick is to start the VM, then go to edit/Virtual Machine, and in there you'll find an option to change the Boot order to CD first.

In my case, this only partially fixed the problem, perhaps because I'd previously botched things by following other advice on the internet. The solution for me was to completely deinstall parallels (using the _installer_, weirdly), then reinstalling it. Be warned that this might then need you to reactivate your windows installation.

J1 visas at the London US embassy

The US embassy website at http://london.usembassy.gov makes applying for a J1 visa appear to be an intimidating and unpleasant process. It's big on the "don'ts" - Don't bring a mobile phone, don't expect to be allowed inside with a bag, don't arrive too early or too late. Then there's the forms: half a dead tree's worth, requiring you to list your experience in nuclear, chemical and biological weapons, every foreign country you've been to in the last ten years (the form was designed by an American...right? They only give you a box big enough to write "Mexico and Canada".)
With a start like that, it's hardly surprising that the actual experience is, in fact, a whole lot better, at least if you're white, middle class and British.

It's still expensive though: for my family of 3 the bill was:
$100 X 3 visa fees
$100 SEVIS fee
£15 mail courier
£170 transport to, from and around london
£15 phone call to make the appointments
------
£400

So, it's worth getting the paperwork right first time.

Ingredients for a J1 (and associated J2) visas:

• DS2019 forms for everyone - these should be provided by your sponsor

• An appointment at the Embassy in London (the Consulate in Edinburgh doesn't do visas. I wonder what they DO do.)

• The appointments are booked via a phone line at £1.20 per minute
• After you make the appointment, you will receive via email an appointment letter and a payment receipt for each member of your family
• Visa application forms for everybody - this is form DS156, which you complete online, and then print out.
• Contact forms DS158 for everybody. This is a PDF file that you print out, and then complete (unless you're lucky enough to have a PDF editor).
• Form DS157 for males of military age (and assorted other categories such as scientists). This is where you have fun listing your chemical warfare experience. It's also a PDF that you print out.
• A SEVIS fee receipt - this is a receipt that you've coughed up the $100 to take part in the program. You can print this off from the web after you've filled in the online form. Note that they don't tell you that you can use this as official proof until you've already agreed to pay an additional $30 to have the certificate couriered over from the US.
• passports for all the family
• One passport photo for each family member.
  

What happens at the embassy
You show up at the embassy shortly before the time on your appointment letter and join a queue. There's one queue (red) for US citizens doing US-citizen things and one queue (yellow) for the rest of us (though when I was there, there was noone in the red queue). At some point a friendly english girl comes down the line and checks your appointment letter, crosses you off a list of expected people, and ushers you on to the next queue at the security checkpoint. At around your allotted time you are waved forward into the checkpoint, which is a portacabin containing an airport style xray machine and a cheery Australian chap. Your documents are looked at again, and you have to put your stuff through the xray machine. There's nothing here that's any more scary than going into an airport departure lounge. Off you trot round the outside of the embassy following the "visas" sign, up some steps and to reception, where your appointment letters are checked again, and you're given a sticker with a number on it. You go into a waiting room and, well, wait. Eventually your number is called and you are told to go to a counter window, where all your documents are taken and examined. These booths are also manned by surprisingly friendly (since it must be a tedious job) Brits and Australians. At this point you get to play with the finger print machine. You're given a blue form with your sticker attached and told to go and sit down and wait again. Tum-de-tum. After an hour or so you get called again, this time to the booths down the corridor for your "interview". If you were expecting an interview behind closed doors with a guy with a rubber hose and a desk light then you'll be pleasantly surprised. Again, the interview takes place at a counter window, in my case with a charming and friendly girl who ought to have been working for the tourist board, not the embassy. This job only seems to be trusted to Americans though, since they presumably have a bigger incentive to keep ne'er-do-wells out of their country. You will be asked about your research project, but we're talking about delivering your elevator pitch here...it's not a viva exam. Click click, stamp stamp. Your visa has been granted. The whole interview took about 5 minutes. Including waiting time, the process takes about 2 hours (though I was told it was a particularly light day). From the order the numbers were being called it was clear that some people had been waiting considerably longer, presumably for being too muslim, too dark skinned or having too interesting a police record. Finally, you take your blue form to a counter at the back of the waiting room where you hand over £15 pounds to pay for the safe return of your passports. I guess you could skip this bit, but it would render the trip a little pointless.

Frequently Asked Questions
Well, I was was asking them, anyway.

• How long does the appointment phone call last?
• At £1.20 a minute, you'd expect them to milk it for all the cash they could get, but mine proceeded at such a rapid pace you'd think it was them paying, not me. Everything was done in about 10 minutes.
  
• Do children need to attend?
• Apparently, children under 14 don't need to go.
• Can children attend?
• Yes. They advise that the embassy isn't the most fun place in the world for a young child, but you're not prohibited from taking child + pram into the embassy.
  The pram will probably need to go through the xray though.
• What about my mobile phone, key fob etc....?
• The website says these aren't allowed. It's lying. When you go through security they'll be taken off you and stored till you return.
• The website says that the visa photos need to be 2 inches square.
• Normal UK passport sized photos seem to be acceptable.
• Are food and drink allowed in?
• They say that you can't take liquids in, and I've no reason to doubt this. However, there's a cafe inside that serves tea, coffee and pop. Beware that it closes at 3ish though.
• Can I take a bag in?
• The website says that you can't take a large rucksack in....I think they mean one of those 70 litre jobs. I took in a reasonably large briefcase. From the setup I expect that they'll tolerate anything you could take as hand luggage on a plane, though their patience might be more limited on busy days.
  

Faster pussycat

"...but Java's so slow...."

1) Java's bytecodes are interpreted by a virtual machine, therefore Java can never be as fast as a statically compiled language such as C
2) Java's VM can perform dynamic optimization in ways not available to a statically optimizing C compiler, therefore Java can outperform C.

The web is full of opinions on which is the fastest language and why. There are plenty of benchmarks proving once and for all one view or the other. However, you never really believe it unless you've tried it yourself. So here, for the first time ever is conclusive proof that really there ain't much in it one way or another.

My completely unscientific test case: an algorithm to sum the first N Fibonacci numbers. The numbers themselves are calculated by a deliberately naive recursive algorithm - don't try this at home. The running time grows exponentially with N. However, it is easy to get a good range of running times. The algorithm can be coded almost identically, line for line, in my 3 target languages of Java, C, Python.

Here are the results:

N	Java (client vm)	Java (server vm)	C (gcc standard options)	C (gcc -O3)	Python
0	0.2	0.2	0	0	0
10	0.2	0.2	0	0	0
20	0.2	0.2	0	0	0
30	0.3	0.2	0	0	1.4
35	0.5		0.4	0.2	15
40	2.5		4.8	1.8	171
45*	24.5	20.6	52	19.8
50	272	232	600	227

*For N>=45 the result overflows when using 32 bit integers. Here's some results using Java longs and C long longs (64 bits):

N	Java (server vm)	C (gcc -O3)
45	21	23.5
50	221	265

No doubt you can find algorithms (and better C compilers) that change the results. But change them enough for you to care?

---

Details:
The tests were run on Ubuntu Linux running in a Parallels VM on a 2007 model Macbook Pro with a couple of gig of RAM.
The Java code was compiled and run with Java 6, the C code with gcc, and the Python code run with Python 2.4.3
Times are the sum of user and system time in secs, recorded to the nearest 0.1 of a sec, and the tests were run a handful of times until I reckoned the time looked about right. Times include any VM startup times.

Boxplots for beginners

How to create Boxplots in R
Refs:
http://en.wikipedia.org/wiki/Boxplot
http://www.r-project.org/

Suppose you have data such as:
number_of_threads thread time
1 1 10
2 1 20.5
2 2 19.5
3 1 30
3 2 25
3 3 35

This table represents made up data describing some system testing, where the system is exercised with 1,2,3... concurrent users. You want to produce a boxplot showing the timings for each number of concurrent users. Here's the magic incantation in R:
Assuming the above file is saved to data.txt
1) Use R's Misc menu to change to the correct working directory
2) Load the data into a dataframe with
myresults = read.table("data.txt", header=TRUE)
3) Generate the boxplot with
boxplot( time ~ number_of_threads, myresults)

To jazz it up with some axis labels:

boxplot( time ~ number_of_threads, myresults, xlab="Concurrent users", ylab="time")

Adding several boxplots on the same axis:
boxplot( time ~ number_of_threads, myresults, add=TRUE)
*Warning* - if you don't see your new boxplot, then it's because for some nutty reason the plot doesn't automatically rescale, and you need to set the scale explicitly with ylim=c(0,40) or similar.
Making the boxes a particular colour:
boxplot( time ~ number_of_threads, myresults, col="yellow")
and adding a legend:
legend(2,9m c("plot1","plot2"), fill=c("red","yellow"))

http://www.flickr.com/photos/josiefraser/532394229/in/set-72157600317386945/

Our Emerge slide.

The Web 2.0 Expo, San Francisco

Audio files from some of the talks:

Check out my Public Files on myDataBus!
ArchitectureforHumanityWeb2.0Expo.mp3
ArchitectureforHumanityWeb2.0Expo.mp3
BadgesandWidgetsWeb2.0.mp3
BuildingSMSWeb2.0Expo.mp3
BuilttoLast.mp3
GoogleWeb2.0.mp3
JeffBezosWeb2.0Expo.mp3
JeffBezosWeb2.0Expo.mp3
LaunchPad1Web2.0Expo.mp3
LaunchPad2Web2.0Expo.mp3
LocationtoanappWeb2.0.mp3
MashupsincompleteWeb2.0.mp3
Mobile2.0Web2.0Expo.mp3
StateoftheWeb2.0.mp3
Syphilis.mp3
Provided to you by

Converting jpgs to ps or eps

A bit of googling finds a number of commercial and shareware packages that will do this task, but you can also do:

jpegtopnm MyDog.jpg | pnmtops > MyDog.ps

on a unix machine.

http://en.wikipedia.org/wiki/Portable_Pixmap_file_format

Moving mail to gmail

I've decided to move completely over to gmail so that I don't have to configure my mail clients to deal with umpteen different accounts. I also want to store all my legacy mail so it's all searchable in the one place. How do I upload my Thunderbird mail files to gmail?
This: http://www.marklyon.org/gmail/download.htm seems to do the job. It's a small python app that goes through your Thunderbird mbox files and forwards them all. It's slow, and it's going to mess up your emails' timestamps, but it does the job.