[bjoli]

As a guile fanboy, I doubt outperforming guile is very hard (even though it is fast enough for most uses).

LuaJIT is most certainly faster than guile, but it isn't a very good comparison. Guile is far from the fastest lisp (or even scheme, for that matter), whereas LuaJIT is probably the best JIT on the planet.

[bakpakin]

That's true. I don't want to criticize Guile or Lisp implementations in general, which have a number of features that Lua can't easily emulate (a numeric tower, true continuations, probably a whole lot more I'm not aware of), but I think Guile and Lua have very similar uses as embedded scripting languages (small, and with fast incremental compilation). Chances are if you using guile you may have considered Lua.

As for use-cases for Fnl, I would say it's more applicable for places where one would use Lua or Guile, rather than something like SBCL or any really fast, compiled Lisp.

Lua makes a pretty good dynamic language target, though, because of the many great implementations and small language spec.

[bjoli]

I have often asked myself how LuaJIT can be so fast. It runs laps around every other JITed dynamic language, even fast ones like JS-v8. First of all: Mike Pall, but secondly: lua's semantics must lend itself very well to modern optimization techniques.

LuaJIT is pretty friggin great and I have embedded it a couple of times with great success :)

I do however preferred guile model for multithreading with one instance that an spawn multiple threads, and that can be used safely from multiple threads,but that is just amatter of taste. If you want to spin up multiple instances, guile isn't for you (although you could use multiple threads in a single instance).

So whatever floats your boat :) There was some work implementing lua on the guile VM, which would have been cool.

[WalterGR]

LuaJIT is probably the best JIT on the planet.

Where can I learn more about how LuaJIT compares to other JITers?

[bjoli]

Mike Pall has written about it in some.places online (googling is a good idea), an he has also written quite a lot about LuaJIT and JITs in general on Reddit:

https://www.reddit.com/user/mikemike/comments

[wruza]

LtU has an old, but interesting thread. Can’t tell how much details changed from that time, but since 1Gb limit was removed from LJ recently, it is my The Only Dynamic Language to Consider.

  http://lambda-the-ultimate.org/node/3851

[bjoli]

Mike Pall indulges in some (well deserved) gloating far down in the thread:

LuaJIT also does: constant folding, constant propagation, copy propagation, algebraic simplifications, reassociation, common-subexpression elimination, alias analysis, load-forwarding, store-forwarding, dead-store elimination, store sinking, scalar replacement of aggregates, scalar-evolution analysis, narrowing, specialization, loop inversion, dead-code elimination, reverse-linear-scan register allocation with a blended cost-model, register hinting, register renaming, memory operand fusion.

Due to the nature of a trace compiler, it implicitly performs partial and interprocedural variants of all of them. And many traditional optimizations, like straightening or unreachable code elimination are unnecessary.

All of that in 120KB for the VM and 80KB for the JIT compiler. And I didn't need 15 years and a billion dollar budget for that, either.

I'm planning to add value-range propagation, array-bounds-check elimination, escape analysis, allocation sinking, if conversion, hyperblock scheduling and auto-vectorization. Anything I forgot? I'll see what I can do. :-)