Hi, list!
I've got an impression that LJ2 b2 does not optimize functions with
varargs.
I should have digged more before asking, sorry if this came up before.
Anyway.
I'm running this silly benchmark:
http://github.com/agladysh/luamarca/blob/master/bench/arguments.lua
luajit2
-------------------------------------------------------------------
name | rel | abs s / iter = us (1e-6 s) / iter
-------------------------------------------------------------------
assert_is_alloc | nan | 0.00 / 10000000 = 0.000000 us
plain_assert | nan | 0.00 / 10000000 = 0.000000 us
assert_is | inf | 0.01 / 10000000 = 0.001000 us
args_select_simple | inf | 3.23 / 10000000 = 0.323000 us
args_recursive_simp | inf | 3.26 / 10000000 = 0.326000 us
args_recursive_ln | inf | 3.63 / 10000000 = 0.363000 us
luajit -O
-------------------------------------------------------------------
name | rel | abs s / iter = us (1e-6 s) / iter
-------------------------------------------------------------------
assert_is | 1.0000 | 4.13 / 10000000 = 0.413000 us
plain_assert | 1.0847 | 4.48 / 10000000 = 0.448000 us
args_recursive_simp | 1.4189 | 5.86 / 10000000 = 0.586000 us
args_recursive_ln | 1.4383 | 5.94 / 10000000 = 0.594000 us
args_select_simple | 1.7724 | 7.32 / 10000000 = 0.732000 us
assert_is_alloc | 3.0993 | 12.80 / 10000000 = 1.280000 us
lua
-------------------------------------------------------------------
name | rel | abs s / iter = us (1e-6 s) / iter
-------------------------------------------------------------------
plain_assert | 1.0000 | 11.86 / 10000000 = 1.186000 us
assert_is | 1.0793 | 12.80 / 10000000 = 1.280000 us
args_select_simple | 1.5776 | 18.71 / 10000000 = 1.871000 us
args_recursive_simp | 1.7083 | 20.26 / 10000000 = 2.026000 us
args_recursive_ln | 1.7749 | 21.05 / 10000000 = 2.105000 us
assert_is_alloc | 2.0135 | 23.88 / 10000000 = 2.388000 us
It seems that in LT 1 recursion is the fastest way to walk through
varargs. In LJ2 it is the slowest way. Would it always be like this or
is it just some beta version artifact?
I want to write fastest possible arguments() function for LJ2.
I remember that LJ2 does not do full-blown optimization yet, so, most
likely, it is too early to say anything yet. I'm fine with waiting for
the definite answer.
But, perhaps, something is known at this point. I use vararg a lot
when I write generic code, so I want, from the beginning, to write it
in the way LJ2 would like it.
Alexander.
P.S. To reproduce, clone http://github.com/agladysh/luamarca
<http://github.com/agladysh/luamarca/blob/master/bench/arguments.lua>
(or download GitHub snapshot) and run
$ ./run_benchmark.sh bench/arguments.lua 1e7
You should have luajit2 somewhere in path.
