Speed tips?

[David Given <dg@...>]

I've just rewritten one of my tools in Lua. Previously, it was in C++, and was 
a badly-designed mess that was practically unmaintainable. The Lua version is 
much cleaner, has a more straightforward design, and takes, unfortunately, 
about ten to fifteen times as long.

As a result, I've been going through looking for places where I can optimise 
it. So far I've managed to shave off about 40% of the time, but it's still 
taking about seven seconds to run. My program is a C++ preprocessor that has 
to be run every time I compile a source file, so seven seconds is 
unacceptable.

What tricks are there that I can use to speed up Lua?

I know the one about global variables being slow. Just adding a 'local' in 
front of one variable took two seconds off the total time. Unfortunately, my 
program is divided into multiple source files so that I can't make all my 
globals into local variables; require() and dofile() both seem to execute 
their code in a new chunk with no upvalues. Are there any ways of getting all 
my code into one chunk without cut-and-paste?

Would recompiling the lua interpreter to use integer arithmetic make an 
appreciable difference? My program doesn't use maths very much.

Any other suggestions?

-- 
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