Re: Faster 'generic for' for raw table

云风 Cloud Wu <[email protected]> 于2026年6月12日周五 20:42写道：

> a minor optimization would be valuable. In many cases, Lua's function
> calls are still relatively slow. When optimizing performance hotspots,
> we can use code generators to inline function calls into flat code.
> However, iterating raw tables remains unavoidable. If the language
> itself could provide a way to iterate raw tables, it would be very
> useful

If we want to avoid calling pairs/next, storing the raw table's keys
in a sequence (like a list) can often double the speed. For example,
consider this code

local t = {}
for i = 1, 100000000 do
  t[i] = i
end

local ti = os.clock()
local sum = 0
for k,v in pairs(t) do
sum = sum + v
end
ti = os.clock() - ti
print(ti, sum)

If we cache the keys into a sequence table first :

local keys = {}
local i = 1
for k in pairs(t) do
  keys[i] = k
  i = i + 1
end

And then use numerical for loop instead,  It also has twice the performance.

local ti = os.clock()
local sum = 0
for i = 1, #keys do
  sum = sum + t[keys[i]]
end
ti = os.clock() - ti
print(ti, sum)





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