Erik's Blog

Interplanetary billards

noreply@blogger.com (Erik Corry) — Sat, 19 Jul 2008 19:33:00 +0000

If you've ever wanted to play at being a god then perhaps you'll find the University of Chicago's solar system simulator to be as much fun as I did. Here you get to set up moons, planets and stars, press the start button and see what happens. Most of the time it's a demolition derby. The bodies are obviously made of glue, because nothing escapes the frequent collisions.

Making any orbital system stable with 3 or more bodies is well known to be quite difficult. However, it's easy to see in the simulator that if you keep the masses of all the bodies but the central sun down then it gets much simpler, at least on the time scales on which I can be bothered to keep watching. Starting 3 planets at distances of 142, 100 and 50 with velocities of 130, 150, 170 gets you a nice 3-planet solar system which might be OK to live in as long as the planets are much smaller than the star. Increase their sizes and things get interesting in the sorts of ways that wouldn't give evolution time to work its magic.

There are ready made systems with planets, moons and even a dual star where one of them has a planet. When I got tired of playing with them I tried making more of my own. Two planets at radius 140 and 160 with speeds of 137 and 103 will make a dual planet system that looks fairly stable. This would be something like having a moon the size of a planet, not entirely unlike the world in Ursula K. LeGuin's The Dispossessed. Again, it works best with smallish planets.

The somewhat more serious, but not nearly as fun simulations at Princeton also illustrate that making stable several-body solar systems is just not an easy thing to do. Even some of the ones that start off well, such as the 3-body Lagrange orbit or FigureEight5 quickly degenerate into what looks like a drunken game of pool, played with magnetic balls. Still, who would have thought that the figure of eight with 3 bodies was stable?

So it's vital that You budding solar system building deities note how important it is to keep the size of orbiting satellites down if You want more than two of them in your system. If You keep them small enough, You can even have a stable million-body configuration, as shown in this paper about Saturn's rings. I may be old-fashioned, but I always feel that having at least one planet with prominent rings in your solar system shows an attention to detail that is appreciated by any sentient life You manage to breed.

Broken link of the day

noreply@blogger.com (Erik Corry) — Sun, 04 Nov 2007 16:59:00 +0000

Here in Denmark almost all our interactions with the state bureaucracy can be done online. We can do our taxes online, and a thousand other things. That's great.

Until now a lot of the web pages involved were on www.danmark.dk and www.netborger.dk (netborger = net citizen, nothing to do with the Borg). Now they have been consolidated on borger.dk. I suppose in some way this makes more sense, but it means that thousands of links have been broken. All links to places on danmark.dk now link to the front page of borger.dk. That's painful enough, but the netborger.dk domain has just been completely removed from the net. There's no clue as to where the content could have gone.

I just hope they haven't dropped the domain completely. Because it will be hawking online casinos really soon if they have.

Reuse of neurons

noreply@blogger.com (Erik Corry) — Thu, 01 Nov 2007 19:20:00 +0000

Few things are as annoying as having to switch between different keyboard layouts. It took me several years to get rid of the nervous twitch caused by switching between German QWERTZ keyboards and non-German QWERTY keyboards. The nervous twitch when writing my name, worrying about whether I had yet again written "Corrz" has only recently worn off.

After leaving Germany I settled on the Danish keyboard. It's a great keyboard for English, Danish and German. For programming, the placement of the {} braces can be annoying so I have a couple of keyboard macros in my .vimrc file:

map! hh {
map! jj }

The letters 'jj' and 'hh' occur very rarely in normal text so this doesn't interfere with non-programming use of vim.

So, happy as I am with my new employer-provided MacBook Pro, I'm not happy about the differences between the normal Danish PC keyboard layout and the one the Mac supports. It's particularly annoying on external keyboards, almost all of which have the PC keycaps.

It's not that I am totally opposed to changes in keyboard layout if they are justified. The most obvious improvement to the standard Danish PC keyboard is to get the rid of the currency symbol that squats like a belligerent drug addict in the penthouse of the '4' key. This symbol was invented as a placeholder for various local currency symbols in the days of 7 bit character sets on non-connected washing-machine-sized machines that processed accounts using reels of tape and chugged along with less processing power than a modern day SIM card. But now, what on earth could be the justification for a symbol that means "some currency, but we don't know which one". Find out and get back to us with the answer, dammit! In these days of Unicode and a three-letter currency abbreviations the only reason for keeping the running pancake in such a prominent position must be anti-Americanism or a misplaced sense of vague internationalism. I suppose it could be to annoy perl programmers and vim users.

Unfortunately, instead of turning this piece of prime keyboard real estate over to the rightful owner, the dollar sign, the Mac people have replaced the currency symbol with the Euro symbol. While marginally more useful this is no help for those of us that need the $ symbol (relegated to shift-alt-3) and conflicts with the standard placement dictated by the Eurocrats (alt-e). Granted, the Euro placement is a hugely verbose demonstration of why you shouldn't let bureaucrats design computer equipment (yes, it's a Word file), complete with a class system for keyboard symbols (level 1, level 2 and level 3 - it is imperative that the Euro shouldn't be on a less prestigious level than other major currencies). However, now they've settled on an standard, there are advantages to following it.

So without further ado, here are a couple of MacOSX keyboard layouts for Danish keyboard layouts. If you are the sort of person who looks down while typing they will allow the characters on your unseen screen to match the keycaps you are looking at. If you have parts of your reptile brain dedicated to the placement of the keys it will allow you to conserve neurons and nerves needed to learn a new layout and (not least) switch between the layouts. They are made with Ukelele and can probably be usefully combined with the use of DoubleCommand. I hope they are useful to someone other than me.

Job at Google

noreply@blogger.com (Erik Corry) — Mon, 08 Oct 2007 20:04:00 +0000

Well, after a fairly long process, I finally got a job at Google in their Aarhus office. I'm very happy about this, but I can't say a lot about what I'm doing there. I'm employed as a software engineer, which won't come as a shock to anyone who knows me.

They interviewed me for around an hour on the phone, then for around an hour in Denmark, then flew me to Trondheim for several more interviews. Most of the interviews involved writing some code on a whiteboard in a language of my choice.

I've been there a month now and as always in a new company it's a challenge to get up to speed. So far, the best thing about it is the colleagues, and the worst thing about it is the version control system. There's an interesting video of Torvalds talking about such issues on YouTube and probably other places.

What I hope I can say is that, in my experience so far, Googlers take the idea of 'not being evil' seriously. But of course, if we were all evil then I would say that too!

Boggle your mind

noreply@blogger.com (Erik Corry) — Mon, 21 May 2007 09:01:00 +0000

Perhaps I'm the last in the blogosphere to discover it, but this art about statistics and the environment was very impressive.

Covering your Fannie

noreply@blogger.com (Erik Corry) — Fri, 02 Feb 2007 07:58:00 +0000

Over at Mish's doom and gloom financial web site there's an interesting article on GSE's. When I say interesting, I mean it's interesting to me. I'm the sort of person who like to read books like my Christmas present this year, about how a bunch of very ambitious financial geeks nearly crashed the financial world in 1998. I also like other stories of financial madness.

The essential point of Mish's and William Poole's warnings is that when you are investing you have to balance risk against exptected return. If the investment is risky you expect to get a higher rate of return, and if it's safe you make do with a lower rate of return. Bonds from (ie. loans to) the government sponsored enterprises responsible for a large part of the mortgage market in the US have very low rates of interest. This indicates that investors think they are almost risk free. They think they are risk free because they imagine that the government is backing them and will bail them out in the event their huge ~~bets~~ derivatives positions go wrong for them. When I say huge, I mean (in the case of the two largest and most ridiculously named, Freddie Mac and Fannie Mae) around $4470000000000, which is about the same size as the US public debt held by the public. Of course Fannie and Freddie also have assets, so we are not talking about net debt, but the comparison is just in case anyone got lost in the zeros.

If Fannie's and Freddie's debt (bonds) are much more risky than the investors think they are, then that's bad news for the investors. They are not getting the return they should from their investments. Looking at it another way, they are more at risk of losing their investments than they think they are. So who are these silly investors? There's a good chance that your pension fund is one of them. They are, after all, some of the biggest investors in bonds.

(It isn't just a phenomenon restricted to US monoliths with silly names either. Risk spreads (the premium you get for taking a risk with your money) are at a very low level everywhere. In effect, the markets are saying things are safer than they have ever been.)

Perhaps your pension fund told you that they have a guaranteed minimum rate of return on the money you are planning to use for your retirement. So if they lose a lot of money because they underestimate risk then you still get to retire to the Florida Keys (assuming they are still there by that time. Or perhaps not.

At least here in Denmark, your pension probably only offers you a guaranteed average return, not a guaranteed return every year (Danish link). And at some point in the future they might decide to change that unilaterally (da). The first pension company has already done that (da) here.

So please put your seats in a vertical position, fold up your trays, and brace yourselves for a risk repricing event. Because if you "misprice risk, don't come looking to [the central banks] for liquidity assistance". I hope you found the central bankers' advice helpful. Personally, I found it a little unnerving.

(Partial) Death of the Google Bomb

noreply@blogger.com (Erik Corry) — Mon, 29 Jan 2007 20:03:00 +0000

So Google killed some of the best Google bombs. A search for "miserable failure" no longer links to Dubya's official web page. The search for liar no longer gets you Tony Blair's web page, and most of the other Google bombs have stopped working too. I guess this is good news for litigious bastards.
Still, it's a relief to see that you can still search for Internet Exploder and get the right page. Hmm. Now that I've pointed this out, will they tweak their algorithm again?

Ever wondered where you were on the net. This page has a red dot showing your location in Internet address space. The map, from supergeek cartoon xkcd uses a rather neat integer-to-space mapping, the Peano curve. I used this mapping to map addresses to positions for a video of memory activity for the talk associated with my ISMM paper. The paper was about optimistic stack allocation for Java-like languages and here is the video of memory activity. The pdf of the paper is subject to the following draconian ACM Copyright Policy: "© ACM, 2006. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of the 2006 international Symposium on Memory Management (Ottawa, Ontario, Canada, June 10 - 11, 2006). ISMM '06. ACM Press, New York, NY, 162-173. DOI=http://doi.acm.org/10.1145/1133956.1133978."

The movie perhaps needs a little explanation. It shows the execution of the 213.javac benchmark from the SpecJvm98 benchmark suite with the 10% data set. The rightmost column is the normal parameter/local variable Java stack (it's a single threaded benchmark). The next column is the allocation stack, where the system is stack allocating new objects. The next column is the semispace based first conventional GC generation. The large area is the main heap, which is so large that it is never garbage collected. Grey means unallocated, green means allocated and white means recently accessed. The idea of using the Peano curve to map addresses to screen coordinates is to make it easier to see locality of reference at both the cache line and page level. The stack allocation heuristic being used is "caller" (see the paper for details).

At any rate I find it quite hypnotic to watch. The main visible activity is the semi-space collector ploughing through memory, and switching halves at regular intervals. In fact a large amount of allocation and deallocation is also taking place on the allocation stack (this is the entire point) but it's not as visible since it's taking place in a very small amount of memory (which is also the entire point). The scale is such that the semispaces are each 64kbytes large if I recall correctly.

My password is fish

noreply@blogger.com (Erik Corry) — Sun, 28 Jan 2007 12:14:00 +0000

If you're an active user of the web, you will be constantly asked to create accounts on web sites. For those sites where you really don't care about establishing an online persona or establishing your own true identity there's always BugMeNot which will feed the website some random id and password.

However, there are a lot of sites where you would be sorry to have someone steal your identity. The obvious ones like online banking sites have their own more-or-less secure login procedures, but then there is the middle tier. Ebay, MoneyBookers and Amazon for example are all sites where there would be real privacy and money problems if someone stole your login. Then there are the networking sites. After spending hours a day and years of your life establishing a witty, informed, devastatingly perceptive online persona on some social networking site it would be even sadder to see it hijacked.

So you need secure passwords for these sites. But noone can remember dozens of different passwords, so you have a few choices. Reusing passwords is a popular one, but has obvious huge security problems. Writing them down is a little better, but not much, and it has accessibility problems unless you keep the passwords with you at all time. Letting your browser manage your passwords also has the problem of having them at hand when you need them, especially considering that hard disks don't live for ever.

A newish way to handle those pesky passwords has been implemented by PasswordMaker and in a different version by PwdHash. Here the idea is that you have one master password. The name of the site and the master password are used together to generate a different password for each site. The method used to generate the per-site password is a secure hash function. These functions have the desirable property that if you are given the output of the hash function you cannot feasibly work out what the input to the function was. (However, if you guess the input, you can use the output to check whether your guess was correct).

PasswordMaker and PwdHash are available as convenient browser plugins, which means they are hardly any more trouble to use than just typing in "fish" on every site. If you are on a machine where you can't install a browser extension they both have Javascript versions that you can use just by remembering the web page name. Since they are Javascript-based your master password doesn't leave the machine you're sitting at. I've started using PasswordMaker, and it works fine. I'm told PwdHash is a good product too, and they have a very detailed paper analyzing security risks. (Thanks to Christian.)

The producers of both products seem to have given too little attention to the risk of a dictionary attack on the master password, performed by an evil webmaster (or some evil person who has taken control of a website). Because of the way these schemes work (and this is their advantage in many ways) you only need the master password in order to generate all the site passwords. This means you, the user, have just one thing to remember. However this means that if the evil webmaster guesses your password they can verify it with your site password and then get into all your other accounts.

Now if you've resisted the temptation to use a really dumb password, then you wouldn't expect Mr. E. Webmaster to be able to guess it. You would expect him to be too busy optimizing his site for Internet Exploder or installing adware on your computer. However, both products, in their default configuration, have the problem that two users with the same master password will have the same site password on a given site. For PasswordMaker, the default is not to use the user name when calculating the site password, and for PwdHash they don't have the option of using the user name at all. Instead they allow you to have two passwords, but it's not the default.

The problem with identical master passwords leading to identical site passwords is that Mr. Evil Webmaster can generate a huge list of master passwords and their associated site password ahead of time. If we are in fact dealing with Mr. Evil Website Hijacker, he can use all the other computers he has hijacked to calculate this huge list in parallel. Once he has the list, he just needs to wait until someone uses one of the site passwords in the list, and he has their master password. Needless to say, this is bad news. There are password 'cracking' services right now that use this principle or variations on it to crack fairly difficult passwords.

So I like these tools, but I would urge you to configure PasswordMaker to use your name as a salt and to configure PwdHash with two passwords, where one of them is unique to you. Using your full name or birthday as the second password is not a bad choice here, as long as the real password is secure, because in this case we are using the second password as a salt, not as a password per se. In the case of PasswordMaker, there are hundreds of other options you can configure. Remember that every option you configure you will have to remember if you use PasswordMaker on another computer. My advice is to leave them almost all alone.

I'll still be using normal passwords for high security applications like my stock broker, but I'm going to cut way down on the use of my "1234" password for other sites. Or maybe the passwords I wrote down on a bit of paper. I'm not telling you which it is. That wouldn't be secure, would it?

Bloat

noreply@blogger.com (Erik Corry) — Fri, 10 Nov 2006 19:27:00 +0000

At the moment, my job requires me to look at the Java standard libraries, and my goodness, there is so much bloat there that it's just not funny. I was astonished that the world needed Boolean(String), but apparently we also need static Boolean valueOf(String). They both require a case-independent(!) string comparison which drags in a whole can of Unicode-related worms.

This reminds me of one of the other JAOO talks, by Walter Bischofberger of Computer Tomography GmbH. Their Sotograph tool does analyses of very large software projects in Java, C/C++ or C#. It's able to work at several different levels showing dependencies between classes, packages, modules etc. Bischofberger's standpoint was that keeping dependencies between different parts of a program to a minimum is very important for keeping a program understandable and modifiable. The relevant Anti-pattern is Big Ball of Mud. As a sort of illustration, they showed a graph of a huge blob of mutually dependent classes in the J2SE standard libraries - 1315 of them in all. He also showed it's been getting worse for each release of the SDK.

That's sort of depressing, even for someone like me who isn't quite as sensitive to smelly code as some people can be.

Wot no audit trail

noreply@blogger.com (Erik Corry) — Tue, 07 Nov 2006 17:40:00 +0000

As the US elections get underway it seems there's trouble with the voting machines again. Frankly, it's a mystery to me how the richest democracy in the world continues to make a pig's ear of something as simple as voting in a first-past-the-post system.

Having personally observed the process of a national election vote count in the UK, I'd like to tell the administrators of the USAmerican polls how it can be done. You give every voter a piece of paper, and ask them to put a cross by the name of their preferred candidate. Then you count the bits of paper. And if there's any doubt you can count them again.

That's it.

Not exactly rocket science.

No hanging chads. No Heath Robinson contraptions. No machines that can be easily tampered with.

Of course, you may have to wait a few hours for the results. Woop-de-doo.

Thinking out of the sandbox

noreply@blogger.com (Erik Corry) — Tue, 31 Oct 2006 20:59:00 +0000

I was recently at the always interesting JAOO conference. I was going to blog about the interesting stuff I saw there, but I haven't until now.

So I thought I'd have a play with Google's Web Toolkit. It's a Java compiler that generates JavaScript instead of byte codes as its output. What this means that it's like Java in the browser, only better in many ways.

* You get web style widgets, and you can use CSS to style them. This has the potential to look much better than the typical Java applet look, which is pretty dire.
* The application is not in a sandbox, but deeply integrated with the browser, including the back button, the forms, etc.
* The user doesn't need to install a plugin to use your site

And it's like Javascript, except you don't have to do everything in a prototype-based language with no debugger, no cross browser compatibility, no compile-time checking and no module/package system. So that's a net reduction in suckyness too.

So basically the idea rocks, and the implementation is pretty convincing too. I decided to have a play with it, and within a few hours had a moderately amusing little application. I don't use their clever 'pure Java RPC', the back button integration, the JUnit implementation, the CSS styling of widgets and the integration in the browser. It's just an applet, really. But it took no time, even including downloading GWT for the first time, I had fun, and I was able to debug it in Eclipse using breakpoints, etc. The whole kit and kaboodle.

It's a game of Solitaire the way we used to play it before the Yanks came along and taught us to call Patience Solitaire. The game is here and the source is there.

Lies2

noreply@blogger.com (Erik Corry) — Sun, 22 Oct 2006 12:46:00 +0000

"The world is safer because Saddam Hussein is no longer in power" says Bush, but is it?

Lies

noreply@blogger.com (Erik Corry) — Fri, 08 Sep 2006 21:59:00 +0000

Apparently it's still news that Saddam Hussein had nothing to do with 9/11.

Trust a Murdoch-owned news outlet to attempt to distract us from inconvenient facts like that.

Housing market blues

noreply@blogger.com (Erik Corry) — Mon, 28 Aug 2006 19:48:00 +0000

It looks like the US housing boom is turning into a bust. You'll find lots of horror stories on Mish's blog. Over here there are also definite signs of a sudden slowdown with almost one in 5 houses deals in Copenhagen now taking place at a discount of more than 10% off the listed price. People are predicting a housing crash in Norway too. (Meanwhile, the German market - especially Berlin - looks a bit undervalued to me. Perhaps I'm just confused by crazy Danish prices.)

At the same time, I wonder what is going on in Iceland. Their central bank just raised rates to a hefty 13.5% with more rises 'inevitable'. This comes after a few years where Icelandic companies have been buying companies in the UK and Denmark (where they now own Illum and Magasin, the most prestigious department stores in Denmark). Icelandic money is also financing a new national free newspaper here in Denmark and apparently a thousand other capital-intensive projects. Are they borrowing all that at a rate of 13.5%, the sort of interest rate associated with the Stagflation of the 70s?

One of the companies that Baugur now controls is Keops, the Copenhagen property company who have of course done very well out of the property boom there. They even do "high yield bonds, secured in property, listed on the Copenhagen Stock Exchange". (Yes, Keops is a pyramid builder - I think the intended association is 'large building' rather than 'dodgy financial scheme').

Let's hope the house price booms do achieve that much hoped-for soft landing. (The Bank of England apparently managed a soft landing for the UK housing market after they eased interest rates a little last year). However, instability can spread quickly - the economies of the world are all very closely interlinked. In 1999, small changes in Danish interest rates helped provoke the spectacular collapse of a huge US hedge fund. It's not far fetched to think that a financial meltdown in Iceland could have similar unexpected consequences today.

Those with large amounts of variable-interest rate debt might do well to consider that even Iceland's 2006 interest rate of 13.5% isn't especially high in historic terms. After the 90s and especially the zeroes we have become accustomed to borrowing huge sums for practically nothing, but there's no rule that says that will continue to be possible.

Stupidity Pact

noreply@blogger.com (Erik Corry) — Thu, 24 Aug 2006 19:28:00 +0000

It now looks like Germany will manage to keep the public sector deficit under 3% this year, which means they will comply with the rules for being part of Euroland. Well, actually it would mean that they would comply with half of the rules, which I suppose is a good start: for some reason all the news sources writing about this development forget about the requirement to keep total government debt under 60% of GDP.

So now that they are on track to get onto the right track, perhaps we can forget that nasty business about France and Germany deciding not to bother punishing themselves for breaching the stability pact. I don't think it's excessively cynical to speculate that, had France and Germany managed to stay within the limits of the stability pact, the EU would not have hesitated to threaten to levy huge fines on smaller countries breaching those same rules.

It has turned out that the stupidity pact, far from operating in an automatic (and brutal) fashion, (as the German negotiators wanted, ironically) is a political tool of the EU establishment, with the potential to totally undermine the political independence of any peripheral country that falls foul of its rules. At the same time, it hasn't managed to ensure anything resembling fiscal discipline, as the "under 60%" link above, shows.

Another huge problem with Euroland is the absence of Norway, which makes the Scandinavian part of the map look like a huge flaccid penis, pointing ominously at Denmark. Whoever was responsible for moving Scania around 100km north didn't exactly make that situation any better.

Audiofejl

noreply@blogger.com (Erik Corry) — Wed, 23 Aug 2006 20:02:00 +0000

The audiophile community amazes me every time I stumble over it on the web. Apparently it's perfectly legal to sell stuff like this magic GSIC chip. How on earth a chip is supposed to alter a read-only data medium by having the one spin in proximity of the other, I really don't know. And as for the "Ultra Tweeters", even the passing bats aren't going to get any pleasure out of that one.

Protecting the young and impressionable

noreply@blogger.com (Erik Corry) — Mon, 21 Aug 2006 19:57:00 +0000

Auntie is reporting that old Tom and Jerry cartoons are going to be gone through with a fine tooth comb (not a fine toothcomb!) for examples of unsuitable smoking by the protagonists. Offending scenes will be cut out to protect their impressionable audience.

Clearly there's no problem with letting kids have their minds fried by endless hours of mindless or sadistic violence, but the sight of a cat smoking a cigar might make them slaves to nicotine for life. Is it silly to point out that cutting down to half a packet a day isn't going to redeem Tom and Jerry's ultraviolent, destructive behaviour? Probably it is, and since most of the newer junk they transmit on Cartoon Network is much worse, I guess I should be happy that those two antedeluvian happy slappers are being house trained so they can stay with us in the new millenium.

SUV

noreply@blogger.com (Erik Corry) — Mon, 03 Jul 2006 20:34:00 +0000

It looks like the era of the S.U.V. is coming to an end. It's clear from that news article that anything with high petrol consumption is getting hard to sell. This is just so much deja vu to those that can remember the 70s - yet again the US car industry has been caught with its pants down building oversized vehicles that suddenly noone wants. Not that the Europeans haven't tried to get in on what was, for a while, a very lucrative business, sometimes with comical results.

If the trend continues, then used prices for large SUVs will soon be very low, and there'll be bargains out there. The right thing to do in this situation is to buy some good example of the genre (eg. a Hummer, but never an H2) and put it in somewhere with low humidity, for example a heated garage, or the Mojave Desert. In 30 years' time it will probably be worth something.

What you shouldn't do is actually try to drive it anywhere.

You could always go by rail instead.

All fired (up) and ready to go

noreply@blogger.com (Erik Corry) — Mon, 03 Jul 2006 19:50:00 +0000

Well, Esmertec has closed down the Danish subsiduary, which included my group, so as of today I and my colleagues are looking for new challenges.

Personally, I'd like an obscenely high salary, insanely interesting work, a relaxed attitude to flextime and of course it has to be within commuting distance of Århus.

But first I have 3 months' worth of severance pay to get through, so I guess it's going to be a good summer holiday.

Java liberated a little

noreply@blogger.com (Erik Corry) — Thu, 18 May 2006 08:31:00 +0000

The biggest news from JavaOne this year is the little-noticed fact that Sun's Java license has been loosened up a little. The idea is to make it possible to preinstall Java on Linux distributions.

It's always struck me as extremely annoying that Java wasn't properly integrated in Linux distributions. It's not just the annoyance of clicking through license agreements, downloading and then ending up with files unmanaged by the package system. It's also the difficulties it causes for anyone wanting to distribute Java software on Linux: You can't just specify a standard distribution version as a prerequisite. This is even worse if you wanted to include a Java program in the standard distribution.

Now if Sun had been charging money for Java on Linux it would be clear why it couldn't just be in the standard Linux distributions. But Sun were giving Java away the whole time, they just weren't giving it away in a way that was usable for Linux distributions.

There are of course open source alternatives to Sun's Java. None of them are quite as bug-free or complete as Sun's version as far as I can see, and none of them come preinstalled on the distributions I've tried.

Now Red Hat (and by extension Fedora) have a history of developing GCJ, an alternative to Sun's Java tools. So they may not be interested in including Sun's Java on Fedora. But there are 3rd party RPM repositories, like ATrpms, and thanks to the wonders of Yum they are fairly easy to use. Debian probably won't use Sun's Java until it is hopefully open sourced properly, but some of the Debian-based distributions like Knoppix or Ubuntu may not be so holy.

So I guess my main question re. Java on Linux is why did it take so long

BitTorrent goes legitimate

noreply@blogger.com (Erik Corry) — Fri, 12 May 2006 10:58:00 +0000

The inventor of BitTorrent has struck a deal with Warner Bros. to distribute movies online. I'm not sure why Warner Bros. feel they need to pay Bram to use his technology, but I'm sure he's happy enough about it.

Of course, Warner Bros. are getting into P2P technology not as a way share the videoware. The new system will be fully encumbered, and apparently no cheaper than buying a DVD in the shops. The main motivation for Warner Bros. seems to be getting free bandwidth for the huge download volumes involved.

It's worth asking where this free bandwidth is coming from. After all, someone must be providing it. Unfortunately it seems that BitTorrent just distributes the cost amongst all the ISPs involved. That wouldn't be so bad, but BitTorrent doesn't make particularly good use of the bandwidth. A file in a BitTorrent download swarm ends up crossing the expensive transcontinental links multiple times because BitTorrent users are downloading from each other.

I wonder whether this is why ADSL Internet providers always give such paltry upload speeds. Here in Europe, transatlantic traffic costs the ISP real money, and the more their users make use of file sharing, the more transatlantic traffic they cause.

It was considerations like this that motivated my patch to Azureus which was later turned into a rather popular plugin by some guys I never met. In its current incarnation it displays flags to show the locations of the peers you are currently downloading to or from. (In my version you just got the 2-letter country codes, which was probably more informative, but less colorful.) In fact I think what is really needed is for the peer selection heuristics to be modified to automatically take the distance to the peers into consideration. In a lot of countries there is a free exchange point that the ISPs can use to exchange data without a volume charge. If BitTorrent preferred 1) peers on the same ISP 2) peers on the same exchange 3) peers on the same continent, it would be much more ISP-friendly, which ultimately is good for everyone. It would probably be faster too.

The Julia system addresses some of these concerns. As far as I can work out they use heuristics to determine which peers are close to each other. In fact I think this data could easily be provided by the ISPs, and it would clearly be in their interest to do so. An obvious way to do it would be by storing configuration information in the Domain Name Service database, which is provided for you by your ISP. It's not the first time that the DNS has been abused to store information unrelated to its original purpose. (I seem to remember that someone even 'uploaded' the pgp source code to the DNS back when it was export controlled, thus causing Internet name servers to circumvent the export restrictions.)

It will be interesting to see whether the deal means that P2P technologies are becoming legitimate or whether the project will just confirm the adage that the only part of Video on Demand that is missing is the demand. Given the draconian DRM restrictions planned for the project that's not unlikely. Also, last I checked, the firewall changes needed to make BitTorrent work well were a little daunting for an individual. Finding a way to simplify this would be a big step forward for P2P protocols.

International Symposium on Memory Management

noreply@blogger.com (Erik Corry) — Fri, 05 May 2006 18:58:00 +0000

I'm off to Canada in June to present my paper, Optimisitic Stack Allocation in Java-Like Languages. Funnily enough (!) we don't implement it in our own system (OSVM). One of the reasons for that is that it is actually better suited to larger devices with deep caches than to real time small devices with often no cache at all.

Since ISMM is colocated with PLDI, and since PLDI is one of the top venues in the business I'll also be going to PLDI. I'll be at PLDI mostly as a lowly spectator, though there will be a poster about our VM and the VM we are doing for the PalCom project.

Needless to say I am very much looking forward to the trip. Apart from the flying over the Atlantic part. Still, it should be comfortable enough compared with the route two acquaintances of mine took. It seems that the phrase 'sore behind' doesn't even begin to describe the experience.

Hop hog

noreply@blogger.com (Erik Corry) — Sun, 02 Apr 2006 18:30:00 +0000

Hauppauge (which as far as I can tell is pronounced the way an Australian would say "Hop hog" or the way a USAmerican would say "Hawp hawg") have made a new version of their lovely MediaMVP set-top MythTV terminal. And it seems they've made incompatible changes to they way it boots that make it more difficult to use with alternative software. So if you were planning on running your own software on it be careful which one you get. The new one is called 'revision H1' and looks different on the front. Apparently the changes are due to the arrival of the wireless MediaMVP which doesn't work with MVPMC either.

I'm sure a way will be found out to get these things to boot user-supplied software. After all, Hauppauge wouldn't just arbitrarily want to limit the ability of users to use their own hardware for their own purposes. Would they? Of course not...

Miscellanea

noreply@blogger.com (Erik Corry) — Thu, 23 Mar 2006 19:00:00 +0000

The man suing the Free Software Foundation using anti-trust legislation has lost. Turns out that RMS isn't an exploiting monopolist after all. Who'd a thunk. Speaking of RMS, is he going soft on his previously tough stand against natalism?

There are 99 days until the new EU directive on poisonous materials in computer equipment come into force. That's the good news. The bad news is that it looks like flat screens are still going to be exempt. So those lovely, slick power-saving monitors are probably going to be filled with poison for a while yet. Still, there are screens coming on the market that comply with RoHC, and there are developments that suggest that the exemption won't be needed for long. Lets hope it doesn't last any longer than the manufacturers need to switch to more environmentally friendly materials and get rid of their stocks of heavy-metal-laced flat screens.

And while we are at The Inq I might as well mention that they have had yet another of their rumours confimed. It seems that the PS3 will be region free for games. Now if the film industry would get a clue and get rid of regions for DVDs too, they'd be doing themselves and their customers a favour. It's a poor advert for DRM when the main currently known use of it is so arbitrary, pointless, ineffective and annoying.