On R performance
On Fri, Mar 9, 2012 at 11:39 AM, Justin Talbot <jtalbot at cs.stanford.edu> wrote:
Isn't R much like Lisp under the covers? Afterall, it evolved from Scheme. Hasn't there been a great deal of work done on optimizing Lisp over the last 30 years? This suggests that instead of dropping the R/S semantics and moving to another language like Julia, the proposals of Ross Ihaka and Duncan Temple Lang could be followed to provide the familiar R/S syntax on top of an optimized Lisp engine.
I think R started off as a Lisp-like language, but since adopting S semantics, it has diverged quite a ways. I think it's better to think of R as a combination of two languages: a dynamically-typed high-level language, much like Javascript or Lua, and an array language, like APL. I think those are the right places to be looking to see how to make R fast. Fortunately, all three of those languages have had a lot of performance work done already that R could just steal from wholesale.
Thanks for the clarification Justin. What about the S4 classes and methods? The design resembles CLOS, and currently this is interpreted R code. Have you addressed performance issues associated with this? What relative impact does this have compared with other optimizations like vectorization? Thanks, Dominick
Another possibility is to implement R/S on top of an optimized virtual machine like the JVM, LLVM, etc.
I like this in theory. But in practice, I'm not sure how well it would work for R. JVM implementations of dynamic languages, like JRuby and Jython run marginally faster (30-40%) than their C interpreters. You do get the Java ecosystem, which is nice, but the performance improvements probably aren't enough to make it worthwhile. And, of course, R already has a pretty good Java connection story. LLVM is a better option; I know there's another group out there looking at R on LLVM. But I'll just note that the really high performance dynamic languages (e.g. Google's V8 implementation of Javascript and Mike Pall's LuaJIT) are hand-rolled JITs. LLVM-based implementations of dynamic languages, like Unladen Swallow, have not been particularly successful. It remains to be seen how well R would map to LLVM. Justin