select(arg_i, ...) vs ({...})[arg_i]

benchmark.lua

--jit.off(true, true)
local r = 3000

do local t = os.clock() local v = 0
    local function f(...)
        local s = ""
        for arg_i = 1, select('#', ...) do
            s = s..tostring(select(arg_i, ...))
        end
        return s
    end
    for i = 1, r do
        v = v+#f(
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7
        )
    end
    print(v, os.clock()-t)
end

collectgarbage()

do local t = os.clock() local v = 0
    local function f(...)
        local s = ""
        local arg = {...}
        for arg_i = 1, #arg do
            s = s..tostring(arg[arg_i])
        end
        return s
    end
    for i = 1, r do
        v = v+#f(
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7
        )
    end
    collectgarbage()
    print(v, os.clock()-t)
end

Results Lua 5.1.4

select: 684000  1.1670000000013
tables: 684000  0.61299999999756
select: 684000  1.1729999999952
tables: 684000  0.64100000000326
select: 684000  1.176999999996
tables: 684000  0.63500000000931
select: 684000  1.1710000000021
tables: 684000  0.63799999999173
select: 684000  1.1719999999914
tables: 684000  0.63199999999779

Results LuaJIT 2.0.0-beta9 (JIT off)

select: 684000  0.632
tables: 684000  0.466
select: 684000  0.632
tables: 684000  0.47
select: 684000  0.635
tables: 684000  0.471
select: 684000  0.635
tables: 684000  0.471
select: 684000  0.636
tables: 684000  0.469

Results LuaJIT 2.0.0-beta9 (JIT on)

select: 420000  0.35199999999999
tables: 420000  0.279
select: 420000  0.351
tables: 420000  0.282
select: 420000  0.36199999999999
tables: 420000  0.28
select: 420000  0.35000000000001
tables: 420000  0.27999999999999
select: 420000  0.35000000000001
tables: 420000  0.28

(Note: The number of arguments had to be reduced from 258 to 170 to prevent crashing.)

Results: Lua 5.1.4

select: 684000  1.1670000000013
tables: 684000  0.61299999999756
select: 684000  1.1729999999952
tables: 684000  0.64100000000326
select: 684000  1.176999999996
tables: 684000  0.63500000000931
select: 684000  1.1710000000021
tables: 684000  0.63799999999173
select: 684000  1.1719999999914
tables: 684000  0.63199999999779

Results: LuaJIT 2.0.0-beta9 (JIT off)

select: 684000  0.632
tables: 684000  0.466
select: 684000  0.632
tables: 684000  0.47
select: 684000  0.635
tables: 684000  0.471
select: 684000  0.635
tables: 684000  0.471
select: 684000  0.636
tables: 684000  0.469

Results: LuaJIT 2.0.0-beta9 (JIT on)

Crashes! Bug?