The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

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:


to read:


and rerun the program.

Lua version of Jumble program
versiontime in seconds
pure Lua 7.74
pure LuaJIT3.57
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.

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