24 Nov
2018
24 Nov
'18
12:50 p.m.
On Sat, 24 Nov 2018 11:14:06 +0100
Fons Adriaensen <fons(a)linuxaudio.org> wrote:
<snip>
The dangerous thing to do is:
// given float p
int i = (int) floorf (p);
float f = fmodf (p, 1.0f);
as you could end up with i + f != p.
The safe way is of course:
int i = (int) floorf (p);
float f = p - i;
Ciao,
Thanks very much for that Fons :)
I'd been mulling over *exactly* that point for some time. My reasoning being
that in the latter case, if the integer was slightly wrong then using it for
the subtraction should give a remainder that was also slightly wrong, but in a
direction that tends to compensate for the error.
The other thing, is why do we need the floorf? Or in the original example
(which was taken from working code) truncf?
A straight cast to int seems to give exactly the same result, and is at least
twice as fast with -O3 and about 4 times as fast unoptimised.
--
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.