dasman’s World

In the process of furthering my Javascript and HTML5 knowledge, I picked as a project an old favourite of mine: an implementation of Conway’s “Life”.

“Life” is an example of cellular automata. All the activity takes place on a 2D grid of cells, where each cell is either “alive” or “dead”. Then from generation to generation whether a cell is born, lives or dies depends on some very simple rules:

• If a cell is alive and has 2 or 3 neighbours, it survives
• If a cell is alive and has less than 2 or more than 3 neighbours, it dies
• If a cell is empty, and has 3 neighbours, a new cell is born

From these simple rules, a huge array of patterns quickly coalesce out of even a random grouping of cells. Patterns like “traffic lights” which switch from 3 cells in a row horizontally, to 3 cells in a row vertically. Or “gliders” a shape that seems to “roll” in a way that means it moves one cell across, and one cell down ever 4 generations. Some people have even implemented simple adding computers using patterns on a “Life” grid, using gliders like electrical signals. Admittedly, probably not the fastest computer ever built…

So, I’ve now built a web page called “WebLife!” that gives you a random grid of cells and lets you single-step or automatically fast-forward through the generations that result. You can access it here:

http://www.asman-it.com.au/weblife/

And the page looks like this:

The page is implemented using an HTML5 canvas as the drawing surface for the grid, and Javascript and JQuery for the logic. As the canvas component is still fairly new, this won’t work on older browsers. I’ve tested it on Firefox 3.6 and Chrome, though, and it works fine there. I haven’t yet tried Internet Explorer, but I suspect it probably won’t work right now.

Using the site is simple enough (if only because the functionality is pretty limited!). Refresh the page to get a “fresh” random grid, then use the Play icon to advance one generation at a time, or the Fast Forward icon to step through generations until the Stop icon is clicked.

I have a few features planned over the coming weeks, including:

• Ability to edit and “draw” your own patterns on the grid
• Ability to change the speed of “fast forward” playback
• Ability to set the grid to “wrap-around” so one side of the grid wraps around to the other side
• Ability to set your own rules, to explore the different patterns that result

As the WebLife page says, any feedback or suggestions are welcome. Happy exploring!

My latest new gadget is a Kindle e-book reader. The lack of ePUB support still concerns me, but that aside, the Kindle is proving to be a fantastic tool. The speed with which I’m getting through my backlog of technical PDFs was worth the investment alone…although my mate Glen Smith’s site “thriftebook.com” (which shows you all the current discounts for technical eBooks) is doing its bit to make sure that the backlog never goes away entirely!

I did encounter an issue early on, though. My Kindle is the 6″ WiFi only model. When I first unpacked it, I connected it to my home wifi network, registered it, and downloaded a few books without any problems. By the end of the first night, though, it refused to connect to the network. Attempting to connect manually through “Settings” results in an error message:

“Your Kindle is unable to connect to the Wifi network. Would you like to enter the password again or manually set up this network?”

After trying a whole host of fixes, a factory reset seemed to clear things up. But the next time I went to use the Kindle, the problem re-occurred. Even upgrading to the latest Kindle firmware (3.02 beta) had no effect.

Finally clutching at straws, I looked at the other half of the wifi equation – my Wifi router. I have a Billion Wifi router (a BiPAC 7401VGPR3). It was running firmware 5.53.s5. Checking out the Billion web page, I found that a few releases had occurred since then, and the latest was 6.02c. I also noticed that the release notes for the 6.01 firmware mentioned “Updated wireless 11N driver to 2.2.0.3″.

Thirty minutes later and I had updated my router, and the Kindle was again connecting flawlessly. Moral of the story (as always) is to make sure that when bugs surface, you’re running the latest and greatest of the relevant pieces of software.

Hopefully this will come in handy for any similarly frustrated souls who are googling for a solution!

It was around a year ago that I put SpamAssassin into my site-wide email setup, and at the time had been pretty happy with the results. The combination of SpamAssassin at the server, and Thunderbird’s spam detection at the client was pretty effective. But over the last 6-8 months especially, the spam situation had been getting a lot worse – around 100 spam messages were making it past the mail server each day. Thunderbird did its best, but there were still 20 or so spam messages that ended up appearing in my Inbox.

So, taking advantage of a long weekend here, I decided to upgrade SpamAssassin.

Wow.

This morning, I opened my Inbox to find 0 spam messages. And a quick look at my “Spam” folder showed that 65 spam messages had been caught – the majority of which had been caught at the server. The new setup has only been running for 10 hours, but that certainly looks promising!

Upgrading to the latest engine no doubt helped, but there have been two specific “extras” that I think are making a big difference.

• I’ve added the Net::DNS perl module to my system – I gather SpamAssassin uses this for RBL lookups and the like. When I first installed SpamAssassin, I didn’t bother with this – it lists a pile of optional modules you’re missing, but is happy to build without them. Net::DNS is one of these “optional modules”. I’d recommend you consider it mandatory!
• I’ve enabled Bayesian filtering. This is the feature that allows SpamAssassin to “learn” which messages are spam. It is a bit of a fiddle – permissions in particular are the big gotcha – but I’m hoping that this will also help keep my spam defences “ahead of the curve”.