Re: LuaJIT string concat

[Geoff Leyland <geoff_leyland@...>]

On 14/04/2011, at 8:59 AM, Pierre-Yves Gérardy wrote:

> Here you are:
> 
>   local sformat, rnd, tostring, a =
>       string.format, math.random, tostring, nil
>   for i= 1,10000000 do
>       a = sformat( "[%s]", tostring(rnd()) )
>       -- a = "["..tostring(rnd).."]"
>   end
> 
> As I told you earlier, I removed table.concat from the benchmark since
> it was a constant factor, likely to dominate the benchmark

Why not profile it? (you'll need to look at the output in a monospaced font)

$ lua -luatrace.profile concat-bench.lua 
...

==================================================================================
Visits  Total   Self  Child Line | concat-bench.lua - Times in milliseconds
----------------------------------------------------------------------------------
     1   0.00   0.00   0.00    1 | local t = {}
   101   0.01   0.01   0.00    2 | for i = 1, 100 do
   100   0.25   0.25   0.00    3 |   t[i] = "abc"..tostring(i)
     .      .      .      .    4 | end
     .      .      .      .    5 | 
     .      .      .      .    6 | local sformat, rnd, tostring, a =
     1   0.00   0.00   0.00    7 |       string.format, math.random, tostring, nil
     .      .      .      .    8 | 
100001   9.28   9.28   0.00    9 | for i= 1,100000 do
100000 648.02 648.02   0.00   10 |   local s = table.concat(t, ",")
100000  96.93  96.93   0.00   11 |   a = sformat("[%s]", s)
     .      .      .      .   12 | end
     .      .      .      .   13 | 
100001   9.40   9.40   0.00   14 | for i= 1,100000 do
100000 644.82 644.82   0.00   15 |   local s = table.concat(t, ",")
100000  60.55  60.55   0.00   16 |   a = "["..s.."]"
     1   0.00   0.00   0.00   17 | end