Path: chuka.playstation.co.uk!news
From: "Nick Slaven" <NickSlaven@Compuserve.com>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: Square Root
Date: Fri, 21 Aug 1998 18:23:02 +0100
Organization: PlayStation Net Yaroze (SCEE)
Lines: 42
Message-ID: <6rkb09$d2j11@chuka.playstation.co.uk>
References: <35DD914A.BBA25235@ndirect.co.uk> <35DD9B1E.3FEAA1E5@scee.sony.co.uk>
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James Russell wrote in message <35DD9B1E.3FEAA1E5@scee.sony.co.uk>...
>> It works fine, but does anyone know a better way to find the square root
>> of any u_long?


Well heres one I rolled meself, I doubt if its better, haven't got time to
check at the mo

u_long ISqrt(u_long X)
{
int  bitmax,Step=0;
u_long V1,V2=0;

// get 1st estimate
for(bitmax=0,V1=X;V1!=0;bitmax++)
        V1>>=1;
V1=X>>(bitmax>>1);

// iterative approximation (takes about 4 steps, "Step" is for unequal
values of V1&V2)
while((V1!=V2)&&(Step++<10))
         {
         V2=X/V1;
         V1=(V1+V2)>>1;
         }
return V1;
}


The iteractive approximation is out of Schaums Basic Maths, the 1st estimate
is something I thought up myself & was rather proud of until I discovered
some very
similar 1st aproximations at
http://www.best.com/~mxmora/umpg/UMPG_II_Math&Algorithms.html

cheers

Nick (S)