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On 4/13/11 11:28 PM, Geoff Leyland wrote: 
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

Hi Geoff,

great profiler module. I am seeing an even more pronounced difference ...


File:line                 Visits    Total     Self    Child | Line
test/concat-bench.lua:5        1     0.01     0.01     0.00 | local t = {}
test/concat-bench.lua:7      101     0.31     0.31     0.00 | for i = 1, 100 do
test/concat-bench.lua:8      100     1.39     1.39     0.00 |    t[i] = "abc"..tostring(i)
test/concat-bench.lua:12       1     0.00     0.00     0.00 |       string.format, math.random, tostring, nil
test/concat-bench.lua:14  100001   295.24   295.24     0.00 | for i= 1,100000 do
test/concat-bench.lua:15  100000  2036.54  2036.54     0.00 |   local s = table.concat(t, ",")
test/concat-bench.lua:16  100000  1048.60  1048.60     0.00 |   a = sformat("[%s]", s)
test/concat-bench.lua:19  100001   292.81   292.81     0.00 | for i= 1,100000 do
test/concat-bench.lua:20  100000  2034.15  2034.15     0.00 |   local s = table.concat(t, ",")
test/concat-bench.lua:21  100000   372.85   372.85     0.00 |   a = "["..s.."]"
test/concat-bench.lua:22       1     0.00     0.00     0.00 | end

You tested that on a mac, too?

Henning