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Hello,
You can also use iterative execution (results in shorter code)
function fN( N, x )
{
for( i = 0; i < N; i++ )
{
x= x^2+1/4;
}
return x;
}
and call it
fN( 1000, 0.75 ); // this is equivalent to f1000( 0.75 )
Also to reduce time needed to compute you should avoid calling
the same function with the same parameters twice (1st time in WriteIf and
2nd time in WriteVal) when it is only necessary to call it once:
function fN( N, x )
{
for( i = 0; i < N; i++ )
{
x= x^2-3/4;
}
return x;
}
Title = "";
for(i=-1.75;i<2;i=i+0.25)
{
Title=Title+"\ni="+
WriteIf(i>=0," ","")+WriteVal(i,1.2)+
StrFormat("%6.2f %6.3f %6.3f %6.3f %6.3f %6.3f %6.3f %6.3f",
i,
fN( 1, i), fN( 5, i), fN( 10, i), fN( 50, i), fN( 100, i), fN( 500, i), fN( 1000, i));
}
This code executes in 0.5 second or less (4 times faster).
This simple example shows the how much speed can be gained by making the code
optimal.
Best regards,
Tomasz Janeczko
amibroker.com
----- Original Message -----
From: "DIMITRIS TSOKAKIS" <TSOKAKIS@xxxxxxxxx>
To: <amibroker@xxxxxxxxxxxxxxx>
Sent: Wednesday, October 06, 2004 8:52 AM
Subject: [amibroker] Chaos:Introductory AFL notes
>
>
> AFL structure helps to reproduce the tables of
> http://www.hypertextbook.com/chaos/11.shtml
> The initial function is applied 1, 5, 10, 50, 100, 500 and 1000 times
> [!!]
> In an Indicator builder window paste the
>
> Title="The orbits of 9 seeds of the f(x)=x^2+1/4";
> function f1(x)
> {return x^2+1/4;}
> function f5(x)
> {return f1(f1(f1(f1(f1(x)))));}
> function f10(x)
> {return f5(f5(x));}
> function f50(x)
> {return f10(f10(f10(f10(f10(x)))));}
> function f100(x)
> {return f50(f50(x));}
> function f500(x)
> {return f100(f100(f100(f100(f100(x)))));}
> function f1000(x)
> {return f500(f500(x));}
> for(i=-1;i<=1;i=i+0.25)
> {
> Title=Title+"\ni="+
> WriteIf(i>=0," ","")+WriteVal(i,1.2)+
> WriteIf(f1(i)>0," "," ")+WriteVal(f1(i),1.3)+
> WriteIf(f5(i)>0," "," ")+WriteVal(f5(i),1.3)+
> WriteIf(f10(i)>0," "," ")+WriteVal(f10(i),1.3)+
> WriteIf(f50(i)>0," "," ")+WriteVal(f50(i),1.3)+
> WriteIf(f100(i)>0," "," ")+WriteVal(f100(i),1.3)+
> WriteIf(f500(i)>0," "," ")+WriteVal(f500(i),1.3)+
> WriteIf(f1000(i)>0," "," ")+WriteVal(f1000(i),1.3);
> }
>
> and, with a few changes, in a new IB window, paste the
>
> Title="The orbits of 15 seeds of the f(x)=x^2-3/4";
> function f1(x)
> {return x^2-3/4;}
> function f5(x)
> {return f1(f1(f1(f1(f1(x)))));}
> function f10(x)
> {return f5(f5(x));}
> function f50(x)
> {return f10(f10(f10(f10(f10(x)))));}
> function f100(x)
> {return f50(f50(x));}
> function f500(x)
> {return f100(f100(f100(f100(f100(x)))));}
> function f1000(x)
> {return f500(f500(x));}
> for(i=-1.75;i<2;i=i+0.25)
> {
> Title=Title+"\ni="+
> WriteIf(i>=0," ","")+WriteVal(i,1.2)+
> WriteIf(f1(i)>0," "," ")+WriteVal(f1(i),1.3)+
> WriteIf(f5(i)>0," "," ")+WriteVal(f5(i),1.3)+
> WriteIf(f10(i)>0," "," ")+WriteVal(f10(i),1.3)+
> WriteIf(f50(i)>0," "," ")+WriteVal(f50(i),1.3)+
> WriteIf(f100(i)>0," "," ")+WriteVal(f100(i),1.3)+
> WriteIf(f500(i)>0," "," ")+WriteVal(f500(i),1.3)+
> WriteIf(f1000(i)>0," "," ")+WriteVal(f1000(i),1.3);
> }
>
> Glenn Elert, the author of this interesting book, writes :"...if you
> wait long enough..."
> The AFL time is ~2sec and it is not bad at all !!
>
> Dimitris
>
>
>
>
>
>
>
> Check AmiBroker web page at:
> http://www.amibroker.com/
>
> Check group FAQ at: http://groups.yahoo.com/group/amibroker/files/groupfaq.html
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
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