2016-06-22 15:16 GMT+02:00 KHMan
On 6/22/2016 8:39 PM, Dirk Laurie wrote:
2016-06-22 12:21 GMT+02:00 steve donovan:
On Tue, Jun 21, 2016 at 10:47 PM, Philipp Janda:
First of all: vararg performance is fine. .... Performance of `select`
is fine too.
Calling it means pushing all of its arguments to the Lua stack -- like
for any
other function.
I also wonder whether we're going to squeeze much more performance out
of this lemon, and whether this is in fact an important lemon.
It is unimportant in the sense that whether traversing the vararg
using select is O(n) or O(n²) seldom matters in practice.
It is important in the sense that it is highly instructive to ponder
the issues involved.
[snip snip]
Hmmm... anyone got an artificial benchmark to test and compare timings? I
don't believe I've seen any timing data so far...
~~~ {benchmark.lua}
function f(...)
local function g(...)
return select('#',...)
end
local t={}
for k=1,select('#',...) do
t[k]=g(select(k,...))
end
return t
end
n=tonumber(arg[1])
print(#f(string.byte(("1"):rep(n),1,-1)))
~~~~
…/tmp$ time lua xxx.lua 10000
10000
real 0m0.315s
user 0m0.311s
sys 0m0.004s
…/tmp$ time lua xxx.lua 50000
50000
real 0m9.695s
user 0m9.679s
sys 0m0.004s
…/tmp$
