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Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 11:34 am
by MyCo
If you can avoid it, do it. It's basically the slowest math operator... Only some functions (eg. log10, exp, pow) are slower.
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 11:38 am
by Nowhk
MyCo wrote:If you can avoid it, do it. It's basically the slowest math operator... Only some functions (eg. log10, exp, pow) are slower.
I'm only using it to "flooring" a value right now:
Will the new compiler have this function? If I don't remember bad, the new int() will do it:
right?
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 11:55 am
by MyCo
for old versions you can use
for truncation, it works as long as x >=0
in the 3.0.9b1 you can use "int" as it works there and is also a lot faster
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 12:06 pm
by Nowhk
MyCo wrote:for old versions you can use
for truncation, it works as long as x >=0
I see (I always think 0.5 was the correct scaling). But why:
return -0 and not 0? On Some "display" value that's weird.
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 12:18 pm
by MyCo
Nowhk wrote:I see (I always think 0.5 was the correct scaling)
0.5 would round integer numbers down too, eg. 2 would round down to 1
Nowhk wrote:return -0 and not 0? On Some "display" value that's weird.
Yeah, floating point system has two zeros, so the sign of the input is carried through the operation
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 12:36 pm
by Nowhk
MyCo wrote:0.5 would round integer numbers down too, eg. 2 would round down to 1
Uhm...
(which is 2-0.5) both rounds to 2 (not 1).
MyCo wrote:Yeah, floating point system has two zeros, so the sign of the input is carried through the operation
And what if I want 0 instead of -0 with this technique?
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 1:41 pm
by MyCo
That's not what I meant, try this to see the difference:
Code: Select all
streamout o1;
streamout o2;
float x = 1;
o1 = rndint(x - 0.49999991);
o2 = rndint(x - 0.5);
0 == -0 in most cases so just ignore it. When you want to display it at some point using green/ruby you can just compare it like: if x==0 then show 0
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 2:31 pm
by Nowhk
MyCo wrote:That's not what I meant, try this to see the difference:
Code: Select all
streamout o1;
streamout o2;
float x = 1;
o1 = rndint(x - 0.49999991);
o2 = rndint(x - 0.5);
Both output the same here. x=1 output 0 (which is "wrong";), while x=2 output 2:
- Immagine_2.png (23.34 KiB) Viewed 31920 times
instead, using x - (x % 1) give to me correct result. Am I wrong somethings other?
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 2:39 pm
by MyCo
Seems to depend on the CPU:
Re: Bitwise strangeness
Posted: Thu Feb 18, 2016 2:42 pm
by Nowhk
MyCo wrote:Seems to depend on the CPU:
Yes, but I can't trust in different CPU
So I'll keep (until I'll upgrade to last version, where int() should floor correctly, I hope)
x - (x % 1) 