On Fri, Sep 26, 2008 at 5:32 PM, Marc Feeley feeley@iro.umontreal.ca wrote:
The conclusion from my benchmarks is quite different. Chicken does not outperform Gambit on these benchmarks. There is so little other stuff happening than call/cc in these benchmarks that it would appear that the performance of call/cc in Chicken and Gambit is essentially the same (to within a few percent).
Why not simply say: chicken and gambit are roughly in the same ballpark?
In the end, I have learned that nearly every performance assumption I made was wrong, and I'm a pretty experienced Scheme coder. Performing benchmarks like this and trying to extract any kind of practical relevance from the fact that program X on implementation Y with optimization settings Z takes 2% longer than on implentation Q. Are you sure you have built both implementations with maximal performance settings? Have you measured how much runtime-performance the memory patterns in this particular benchmark have caused? How do you know how your system configuration and hardware setup influences the outcome? Have you used optimal optimization settings for all implementations for this benchmark? Have you analyzed the compiler output to look for opportunities to tweak those settings for this particular benchmark? Do you know enough about chicken's internals and compiler options to chose the optimal combination (you couldn't, just as I couldn't for Gambit). It's all just assumptions.
The very reason Scheme and Lisp have so little acceptance and are not more widespread is that its implementors are so obsessed with performance (for hystorical raisins, of course), instead of making their implementation easier to work with, more practical and more useful.
Nevertheless I understand this obsession, its lots of fun, after all. :-)
So: CheneyOnTheMTA is an elegant concept that unifies fast first-class continuations, fast allocation, generational GC and not-too-difficult FFI in a relatively simple framework. Chicken's compiler is sufficient, but there are many opportunities to improve performance, some of which will be addressed, but which aren't really that important. A real module system (soon to come!) and 400+ libraries is what will make users happy, not 5% better performance.
I believe that CheneyOnTheMTA is more memory-efficient than other Lisp-implementation techniques. I also believe that the CPS-output of this scheme is more C-compiler friendly and easier to compile on stock machines. I believe that COTMTA (that's a nice abbreviation - I think I'll use that from now on) makes cross-module calls more efficient than trampoline-style, which is important for large code-bases that use separate compilation and dynamically loaded plugins. These are all assumption that may possibly be completely wrong.
Keep up the good work, Marc! Gambit is cool. But chicken is better. ;-)
cheers, felix