Author: Dieter Buerssner
Date: 16:41:53 09/10/02
Go up one level in this thread
On September 09, 2002 at 23:10:20, Robert Hyatt wrote:
>I can't believe _any_ compiler would use .001 since it can't be converted
>to IEEE FP exactly. Dividing by 1000 is far more preferable as 1000 _can_
>be converted exactly.
gcc -ffast-math
Often (mostly?) this is nice. For example
double a, b, c, d;
/* I don't care about the last bit (only this can be different), but about
speed */
a /= d;
b /= d;
/* Or should I write:
c = 1.0/d;
a *= c;
b *= c;
A clever compiler may know, which is faster for this specific architecture.
Many algorithms will work well either way, so one prefers the fastest method.
A strict IEEE-conforming floating point environment, of course must not
rearrange such expressions.
*/
Regards,
Dieter
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