Sunday, 23 November 2008

Scientists are possibly a little obsessive

I'm feeling pretty smug tonight because I finally managed to implement a new way of simulating the Ising model that I'd been thinking about off and on for years. At the same time I'm also feeling a bit sad that I've stayed up until 3am on a Saturday night doing it. I think it's the element of obsessive scientist that comes out occasionally where you have a tea/coffee fueled binge until you've solved the problem - it's probably not limited to scientists.

The reason I wanted to do this will become clear soon (as in I'll post on it). I wanted to simulate a lattice with as many sites as possible so that I can do some visualisation of renormalisation group ideas (again more on this soon). Instead of storing each site inside a byte of memory I store 8 sites in each byte and then use a bit of binary operating to get the bit I need. This means each site now only takes one bit of memory.

That was the easy bit. The hard bit was simulating this setup around the critical point. Critical points in statistical mechanics are incredibly interesting but real buggers to simulate. Fortunately there have been some very clever people who have worked out how to do this. I've not done anything that clever, but I have worked out how to implement a Wolff cluster algorithm using ~ N/4 bytes of memory which I think is good going.

I will post on this again when I've managed to run the programme on our fancy new computer (it's got 8GB of RAM) and have a nice picture to show. I will also explain what the Ising model is and what a critical point is...

Sunday, 16 November 2008

Viva and Backup update

I thought I'd return to backups briefly and say how I was getting on with some of the web based ones. Initially I was using Mozy but after some problems with the software I uninstalled it. I'm too impatient to fix problems with this sort of programme so I ditched it. Live mesh, on the other hand, just worked. I have to say I'm getting on well with it. I don't really have a lot to say about it except that it's relatively unobtrusive and I don't think it's slowing the computer down too much.

In other news I passed my viva! Hopefully this means I can start talking about statistical physics more which is sort of what I wanted to do with this blog in the first place.

Thursday, 6 November 2008


I'm pretty much backup obsessed. Of all the obessions you can have this is probably quite healthy. For example I wish I was a bit more exercise obsessed but what can you do? It's staggering how many people still don't think about backup despite the fact that they switched all their photos and music over to their PC years ago. One hard disk failure and you're buggered - and they fail depressingly often.

At work I've been using this rsync system for years. It's great, I never have to think about it but every day any new work is saved and you can track changes for as long as you like. Unfortunately I could never get this to work in Windows (through cygwin), I think it's a file system thing. Apple introduced Time Machine with their latest version of OS X. This is exactly the same system but packaged up in the neat Apple way as you'd expect. I haven't got this working on remote servers yet but I'll update if I do.

At home I'm still stuck with Windows XP (see earlier posts on why I won't switch to Linux) and I have an external hard drive. I'd really like something like Time Machine but at the moment I have to copy everything each time I backup - this is far from ideal. The simplest, and most effective, long term backup is still to post a DVD to your parents or a friend. It's cheap and it's off-site. The trouble with these last two (my current home setup) is that if my hard drive goes down I'll still lose 2-4 weeks worth of data as I can only be bothered backing up about once a month. Fortunately there is a new (new to me) solution brewing in the clouds.

It seems that storage is becoming sufficiently cheap that companies can now offer large amounts of online space for free. After reading this page I checked out a few of their recommendations. Initially Mozy looked really good but I didn't get on too well with the software so I moved to Microsoft's "Live Mesh". I have to say Microsoft appear to have knocked it out of the park with this one. I already had a hotmail account so setting it up was a breeze. Once it's installed you can just drag whatever folders you want to synchronise with the mesh. After that you just leave it in the background and it quietly makes sure you're files are synchronised. Seems to work well, I'll let you know how it goes.

This is more meant for synching files than it is backup but it obviously serves both purposes. I'm looking to use these kinds of service to fill in the month-6 month backup gap. I'll still use more traditional methods for older stuff. These systems all seem a bit early days and no doubt will improve with time, it's definitely a move in the right direction though.

If I could afford it I'd get a new mac £950 and a time capsule £200. But I can't. Damn expensive Apples. There are other network hard drive options though so that's worth keeping an eye on. Oh, and don't forget the ultimate. Despite being backed up on three computers I still emailed my thesis to my gmail account as soon as it was finished!