See https://blogs.oracle.com/buck/entry/inflation_system_propert... and http://stackoverflow.com/questions/10082523/java-what-is-jit... for more info
Hmm... but my discussions with people who have worked on Ruby execution engines say that Ruby's normal operations are slow (because Ruby is constrained to do many slow things for normal invocations). How does Ruby reflection compare to .NET reflection and how does Ruby invocation compare to .NET invocation?
a + b
a.send('+', b)
add ra, rb, rx
jo
Ruby really isn't constrained to do anything slow for normal method invocations - you can optimise I think literally all of them away entirely if you have a JIT. For normal method invocations this all all solved back in the early 1990s in the research on making Smalltalk fast, but wasn't fully applied to Ruby until my work (and Topaz, Ruby on PyPy achieved similar results around the same time actually). I extended it to work with reflection (metaprogramming).
Everything can be optimized at a compiler or a runtime level. Even if you just scale it back to specific idom-optimizations (as you talk about in one of your talks you've done on your JVM work) you can tremendiously boost speeds by 200 to 300% just by writing operation-specific optimizations.
It's a sad state that because of this preceived "it's going to be slow" that no one seems to be attempting to implement things that Guy Steel and McCarthy implemented way back when. This sort of lazy thinking results in the "Just right it in C" mentality that much of the python community holds.
I'm glad at least you and the JVM people are working on this as this is quite important for all CS-focust disciplines.
You're right. The .Net JIT will only compile a method once, so unfortunately it can't do tricks like this
I'll definitely give this a deeper read.
You should start to do that or, at least, remove the negative bias.
A lot of the cool stuff out there comes from research, whether in academia or commerce, and only reaches the "real world" a long time later.
Yes! I wrote a PhD on making reflection in Ruby fast. It is possible to make most reflection operations run with no peak time performance overhead at all compared to normal operations.
http://chrisseaton.com/phd/
The main techniques needed are dynamic code compilation with speculation and deoptimisation, polymorphic inline caching, splitting and method inlining. Unfortunately I think the .NET JIT isn't dynamic (might be mistaken, not an expert on .NET) so can't do speculative optimisations.
Basically you see what method names have been used last time in a reflective call, and create a little call that's more like a conventional call using those names. Each time you do the reflective call you check the name against the list of names you have created conventional calls for, and use them if you can. You need to make string comparison fast, which can be done using a rope data structure. Then you need to be able to remove the check entirely if the string comes from somewhere you can control, like a constant. Then you need to inline the reflection method so you are just left with the synthetic conventional call.
So it isn't easy! Which is why it isn't usually done. But it's possible.
In Ruby you need to make it fast no matter how hard it is, as Ruby libraries tend to use reflection (they call it metaprogramming) in inner-loop operations.