Optimize performance

[raffomania]

http://lua-users.org/wiki/ProfilingLuaCode could be of help.

[LuminescentMoon]

Love2D uses LuaJIT. According to this page pairs() is not JIT compiled. So any instruction path that uses pairs() would not benefit from the performance improvements of the LuaJIT runtime.

Looking through the code, I believe there are some usage of pairs() that could be replaced ipairs(). Doing so would be a first step towards improving overall performance.

[Nukesor]

Thx for the advice and the website, it looks really helpful.
We are currently looking into some profiling tools as well, so there will hopefully be some progress on this issue soon.

[LuminescentMoon]

LuaJIT v2.1 has a built-in sampling profiler. One of the output formats it supports looks pretty neat:

$ luajit -jp=a spectralnorm.lua 4000
====== spectralnorm.lua ======
 <at>  <at>  3  <at>  <at> 
      | -- contributed by Mike Pall
      | 
      | local function A(i, j)
  10% |   local ij = i+j-1
  25% |   return 1.0 / (ij * (ij-1) * 0.5 + i)
      | end
      | 
      | local function Av(x, y, N)
      |   for i=1,N do
      |     local a = 0
  32% |     for j=1,N do a = a + x[j] * A(i, j) end
      |     y[i] = a
      |   end
      | end
 <at>  <at>  18  <at>  <at> 
      | local function Atv(x, y, N)
      |   for i=1,N do
      |     local a = 0
  32% |     for j=1,N do a = a + x[j] * A(j, i) end
      |     y[i] = a
      |   end
      | end

[raffomania]

Wow, we didn't know about that, thanks a lot. @Nukesor and me are still looking for some time to throw at this ticket, if in the meantime you find out more feel free to open a PR or comment again :)

[LuminescentMoon]

It also has a feature where you could label sections of code as zones for an easier to read profiler output. E.g. a game could make use of an "AI" zone, a "PHYS" zone, etc.