28 Jun
2004
28 Jun
'04
8:44 a.m.
On Mon, Jun 28, 2004 at 12:23:37 +0200, Maarten de Boer wrote:
Hi Erik,
Depending on the ranges of your increment, and the accuracy you
want to obtain, you might consider doing this with integers only.
Yes, for this kind of accumulator thing I often use a hacked up
fixedpoint representation:
typedef union {
int32_t all;
struct {
uint16_t fr;
int16_t in;
} part;
} fixp16;
as you're only ever adding to them, you dont gain much by using floats,
getting the interger part out is really cheap and easy (foo.part.in) and
the fractional part is foo.part.fr / 2^16. Accumulation is done with
accum.all += delta.all. The 32.32 form should be obvious.
I think the struct components need to be the other way round for bigendian
machines though. I really must do something about making that work...
- Steve