Locals vs Globals Benchmark test

Because I haven't posted anything in a long time I'll post a little program that I found and modified to show that it's better to use locals, rather than global variables. It's what you expect it to be, a benchmark test, first it tests with local variables, then with global variables.

Screenshot( not really needed, but I posted one anyway )


For those who're lazy( like me ) you can download with the command below

pastebin get 90kzBp0P benchmark

Direct link: http://pastebin.com/90kzBp0P

I'd of expected it to be a slightly higher difference - it is one array index operation rather than 3 or 4 hashmap lookups (first in the environment, then for __index in the metatable, then in the parent environment). It might be interesting to check other micro-optimisations (a * (1/3) vs a / 3, a * a vs a ^ 2, etc…).

SquidDev, on 06 June 2015 - 04:25 PM said:

I'd of expected it to be a slightly higher difference - it is one array index operation rather than 3 or 4 hashmap lookups (first in the environment, then for __index in the metatable, then in the parent environment). It might be interesting to check other micro-optimisations (a * (1/3) vs a / 3, a * a vs a ^ 2, etc…).

Would it even be worth it?

Creator, on 06 June 2015 - 04:58 PM said:

SquidDev, on 06 June 2015 - 04:25 PM said:

I'd of expected it to be a slightly higher difference - it is one array index operation rather than 3 or 4 hashmap lookups (first in the environment, then for __index in the metatable, then in the parent environment). It might be interesting to check other micro-optimisations (a * (1/3) vs a / 3, a * a vs a ^ 2, etc…).

Would it even be worth it?

That's what I've always wondered… I'm not sure if LuaJ implements constant folding so a * (1/3) might not even have an effect. a * a is quicker than a ^ 2 but I don't know by how much.

SquidDev, on 06 June 2015 - 05:01 PM said:

- snip -

Thanks for the feedback, but this was mostly only made to demonstrate why it's better to use locals, as it can speedup slow programs.
Most new users on these forums tend to not use locals, which is kind of annoying sometimes, but it was the same with me when I was new here :P/>

TheOddByte, on 06 June 2015 - 05:41 PM said:

SquidDev, on 06 June 2015 - 05:01 PM said:

- snip -

Thanks for the feedback, but this was mostly only made to demonstrate why it's better to use locals, as it can speedup slow programs.
Most new users on these forums tend to not use locals, which is kind of annoying sometimes, but it was the same with me when I was new here :P/>

It's really not the most important thing they could learn–not when they're trying to learn functions, how strings and numbers work, string manipulation, etc. It sorta comes toward the end of the basics, and that's because the programs will at least function without locals.
A bigger problem with the newbies is that they go straight ahead and attempt an OS–something that requires a lot of Lua knowledge to do. The 'os'es are typically pointless; the most they feature is a graphic UI, usually without multitasking, and usually more difficult to use and less featured than CraftOS itself.


haha I finished quite a bit faster than you. My processor(I don't think graphics or RAM really matter to CC) is an i5 quad-core @ 3.5GHz. What's yours?

How come local are faster than globals?

Geforce Fan, on 06 June 2015 - 05:46 PM said:

haha I finished quite a bit faster than you. My processor(I don't think graphics or RAM really matter to CC) is an i5 quad-core @ 3.5GHz. What's yours?

I've got a Intel(R) Core(TM) i5-4300M @ 2.60GHz, but I'm on my school laptop so I'm not surprised :P/>

Creator, on 06 June 2015 - 05:56 PM said:

How come local are faster than globals?

TOBIT explained it pretty well here: http://www.computercraft.info/forums2/index.php?/topic/15650-repeating-a-function-every-minute/page__view__findpost__p__150185

TheOddByte, on 06 June 2015 - 06:27 PM said:

Geforce Fan, on 06 June 2015 - 05:46 PM said:

haha I finished quite a bit faster than you. My processor(I don't think graphics or RAM really matter to CC) is an i5 quad-core @ 3.5GHz. What's yours?

I've got a Intel® Core™ i5-4300M @ 2.60GHz, but I'm on my school laptop so I'm not surprised :P/>

Creator, on 06 June 2015 - 05:56 PM said:

How come local are faster than globals?

TOBIT explained it pretty well here: http://www.computerc...post__p__150185

So, you have a school laptop and a not school laptop? And the school laptop is that good?

Creator, on 06 June 2015 - 06:40 PM said:

So, you have a school laptop and a not school laptop? And the school laptop is that good?

Well yeah, it's surprisingly good for a school laptop, it's one of the perks of going in an IT school :P/>

Creator, on 06 June 2015 - 05:56 PM said:

So, you have a school laptop and a not school laptop? And the school laptop is that good?

what?!?!
You've just said he has a school laptop and not a school laptop…

Geforce Fan, on 07 June 2015 - 03:07 AM said:

Creator, on 06 June 2015 - 05:56 PM said:

So, you have a school laptop and a not school laptop? And the school laptop is that good?

what?!?!
You've just said he has a school laptop and not a school laptop…

He probably means

a non-school laptop

flaghacker, on 07 June 2015 - 07:43 AM said:

-snip-

What I think he meant with that is that it's better than ordinary school laptops( I think ).

TheOddByte, on 07 June 2015 - 11:39 AM said:

flaghacker, on 07 June 2015 - 07:43 AM said:

-snip-

What I think he meant with that is that it's better than ordinary school laptops( I think ).

What I meant is that you have a very good school laptop. And alone the fact that you have a laptop for yourself from the school surprises me.

Creator, on 07 June 2015 - 11:45 AM said:

What I meant is that you have a very good school laptop. And alone the fact that you have a laptop for yourself from the school surprises me.

Well that's going in a school in sweden gets you, especially when it's an IT school! :D/> :P/>

TheOddByte, on 07 June 2015 - 11:57 AM said:

Creator, on 07 June 2015 - 11:45 AM said:

What I meant is that you have a very good school laptop. And alone the fact that you have a laptop for yourself from the school surprises me.

Well that's going in a school in sweden gets you, especially when it's an IT school! :D/> :P/>

I should really move to sweden