Re: AClock fork with republican time

[Ingolf Jandt]

On 2006-11-22 23:26:20 +0100 Banlu Kemiyatorn <id@gamesquare.co.th> 
wrote:

> Ingolf Jandt wrote:
> Ah, Ok, Actually you are welcome to criticise my code, I was just 
> kidding.
Once more: I did not want to criticise nor debate, only find out if 
there was something obvious I failed to see.

> But now, for the sake of humor let's do this :)
Ok, for the bare fun of discussing...
> ... It looks to me that my method is faster...
I am absolutely not convinced. The amount of floating point 
instructions is about the same (yes, i have read the rest of the modf 
disassemble of my system). And a handful of MOVs on the stack are 
absolutely neglectible.
2. The code used sacrifices a lot of readability compared to "a/b", 
"modf (a/b,&dummy)" or even "a/b-floor(a/b)". Speed issues should only 
have precedence if there is no choice.
3. If speed did matter in any way the result would have been stored, 
not the computation code copied and pasted many times.

I put the code
    c=a-b*floor(a/b);c/=b;    or c=modf(a/b,&dummy);    or c=a/b;
    x=sin(2*M_PI*c);
    y=cos(2*M_PI*c);
into a loop and played with different inputs. It appears to me that
1. The calculation time of around 1,5(+-0,3)x10^-7 seconds is in each 
case ridicously short compared with the drawing period of ~ 10^-1 sec.
2. "Your code" takes -- depending on the input -- 5-20% _more_ time 
than "mine".
Leaving the mod-ing to the sin/cos functons saves again 10-15% of time.

All this applys of course only to my system. (Even if one could assume 
it for the majority of implementations comparing the speed of library 
functions is like debating about grains of sand whilst heavy rocks lie 
in writing a clean algorithm.)

So long
Ingolf