Re: Why is using single-precision slower than using double-precision

In <3b015c$bt@rational.rational.com> davidm@Rational.COM (David Moore) writes:


[snip]
>programmer can help by using a double temporary instead of floating i:


> double di=1.0;
> for(i=1;i<=N;i=i+1) {
> local = ( (di - 0.5 ) * w ;
> pi = pi + 4.0 / ( 1.0 + local * local ) ;
> di += 1.0;
> }


The above code verges on inaccuracy by keeping an index variable as
a floating point number and incrementing it by a floating point
number. Systematic error is introduced into such an index variable if the
increment quantity does not have an exact binary representation.


--
David B. Chorlian
Neurodynamics Lab SUNY/HSCB
chorlian@sp1p.neurodyn.hscbklyn.edu
davidc@panix.com

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