On 2009-05-09 01:14:56 +0200, Walter Bright <[email protected]> said:
Don Clugston writes about floating point programming in D:
http://www.digitalmars.com/d/2.0/d-floating-point.html
http://www.reddit.com/r/programming/comments/8j10v/real_close_to_the_machine_floating_point_in_d/
Nice
article Don!
on comparing floating points if you have complex operation in between
(like diagonalizations,... or even a simple dot product) I often use
int feqrel2(T)(T x,T y){
static if(isComplexType!(T)){
return min(feqrel2(x.re,y.re),feqrel2(x.im,y.im));
} else {
const T shift=ctfe_powI(0.5,T.mant_dig/4);
if (x<0){
return feqrel(x-shift,y-shift);
} else {
return feqrel(x+shift,y+shift);
}
}
}
because if you sum (as you say later) the absolute error is added, and
the relative one can become very large.
If the result is close to 0 (where the density of floats is very high),
or even 0 by chance, you cannot expect to keep the relative error to be
small, so I cap the relative error close to 0 with an absolute one...
Fawzi
