RE: Arrays oddities
- From: Alain Meunier <deco33@xxxxxxxxxx>
- To: "luajit@xxxxxxxxxxxxx" <luajit@xxxxxxxxxxxxx>
- Date: Mon, 31 Mar 2014 15:08:28 +0200
Demetri,
Thanks a lot. I am absolutely amazed, x6.7 improvement. Almost on par with C
speed for the whole logic.
That is _fast_. And so easy.
I didn't get ffi really well and will need some time to grasp it. Just started
yesterday and wanted to know more about it.
Mike, :) it is not the ffi version that is in production of course, but the
logic (and we cannot change it, since a whole stack relies on it) :D
I am so much into lua, since say weeks, that I think 1-based array and not
0-based anymore.
My mistake. But I treat myself.
Anyway, many thanks both of you, you helped to get my feet wet.
Bye
Date: Mon, 31 Mar 2014 03:29:31 -0700
Subject: Re: Arrays oddities
From: demetri.spanos@xxxxxxxxx
To: luajit@xxxxxxxxxxxxx
2) Good news! If you can rework your problem to more closely align with the
use-cases the optimizer is tuned for you can pick up *much* more performance.
In the spirit of offering something more concrete, try replacing your inner
loopwith this:
local buff = ffi.new("char[64]");
local f = ffi.C.fopen("data.txt","r") for i=0,7281624-1 do ints[i]
= ffi.C.atoi(ffi.C.fgets(buff,64,f)) end ffi.C.fclose(f)
NOTE: There is no error checking here. If you use this in production without
adding error checking then you will be making puppies and kittens sad. Please
think of the innocent animals.
Anyway, this gets me a ~8x global speedup relative to the io/lines iterator and
thearray version is ~10% faster than the table version.
Demetri
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