We started off with Joel Spolsky who is an entertaining speaker, but unfortunately doesn't have as much real content in his talks as he does in his blog.
Next I went to a talk on IronRuby (Ruby on the .Net CLR) They seem to be making good progress. I would have liked to hear more about the details of their implementation. It sounds like performance is a big issue - they are currently about 10 times slower than MRI (Matz's Ruby Interpreter - the original C implementation of Ruby).
I went out at lunchtime and got back just before the sessions were due to start, only to find the ones I wanted to see were all full. This was ironic since in the morning introduction they'd made a point of saying they hadn't sold out and didn't want to sell out because they wanted everyone to get in. I guess I should have got in line earlier. Oh well, I grabbed a latte and worked on jSuneido.
The last two sessions were on Rubinius and MagLev - two more implementations of Ruby.
Rubinius' aim is RiR - Ruby In Ruby - i.e. trying to implement as much of Ruby in the Ruby language rather thin in C like MRI. I was interested to hear they are planning/hoping to use LLVM to optimize their compiler. (I'd looked at this for Suneido.) I found it a little puzzling that one of their reasons for not using the StrongTalk VM was they couldn't understand the source code. But I seriously wonder if the LLVM source code is any easier to understand. If you're going to use another project because you want to skip the effort of writing it yourself, then I don't think it's fair to expect to "understand" it. You have to expect a certain amount of "black box".
MagLev is Ruby on top of GemStone's proprietary Smalltalk VM and including their impressive object persistence facilities. MagLev is claiming pretty amazing performance from their VM - up to 100 times faster than MRI. This seemed to raise some issues with the jRuby guys. Charles Nutter asked a question which came pretty close to saying, "if it doesn't work, you can make it as fast as you want" (MagLev doesn't implement all of Ruby yet.) I wonder if the GemStone VM is really much faster than the JVM? Not that it matters in the big picture because the JVM is everywhere whereas GemStone is nowhere (relatively).
You may notice that although this is RailsConf, none of the sessions I went to were on Rails! It suited me fine since it matched my interests, but I felt a little guilty. Of course, the one session that I couldn't get into because it was full was an actual Rails one. There is of course a Rails tie in to these sessions. It's Rails that has made Ruby so popular and the reason for all these implementations of Ruby is primarily to run Rails.
All in all, a pretty good day. The weather was beautiful, of course, since I was inside all day!