Wednesday, February 03, 2010
Lua just in time
Playing around with Lua is fun, but I've been hearing some good things about LuaJIT, a “just in time” compiler for Lua for the x86 platform (written by a single guy, no less!). Even more amazing, it's literally a drop in replacement for Lua (both the command line interpreter and library).
Okay, I'm willing to give this a try. I download, compile and install it. I then decide to test it using jumble program I wrote in Lua. All I need to do is change one line:
#!/usr/local/bin/lua
to read:
#!/usr/local/bin/luajit
and rerun the program.
| version | time in seconds |
|---|---|
| pure Lua | 7.74 |
| pure LuaJIT | 3.57 |
| Lua + C | 2.06 |
| LuaJIT + C | 1.70 |
LuaJIT easily trounces the Lua interpreter without any code changes (other than specifying a different “interpreter”). The versions with C use a C function to sort the letters in the word and while LuaJIT was faster than the Lua + C version, the very fact that I didn't have to modify any code is fantastic! LuaJIT used the very same C code as the Lua version—no changes or recompilations required!
Very neat!
I just relinked my Lua daemon against LuaJIT, just to test it out, and yes, it worked without any changes. I could even reload the scripts on the fly. And incredibly, it's only about 50% bigger than Lua itself.
LuaJIT is one sweet piece of technology.
