Re: [Paparazzi-devel] Difference Between Fixed-point and Floating-point Schemes

[Christophe De Wagter]

floats have LOWER precision as you need to store the exponent. you loose 13 bits there. in fixedpoint the exponent is written in the code so you can use all 32 bits to store your number:

e.g. in INT you can encode global position with 1cm resolution, while in float it is 2.5m resolution....

floats are much, MUCH slower in non-floating CPU like our ARM autopilots...

-Christophe 

On Tue, Jun 26, 2012 at 6:05 PM, Chris Wozny <address@hidden> wrote:

All,

I had a general question born out of curiousity. I know floating point
numbers are more computationally intensive than fixed point integers
in terms of operations (i.e. multiplication, etc). I was just
wondering, what is the difference then between the int_quat
stabilization subsystem versus the float_quat one (or int_cmpl_quat
versus float_cmpl if the only difference is fixed-point versus
floating point)? In an ideal world where we could compute both
operations just as quickly, is there one which is better than the
other due to higher precision of floats? These aren't specific to any
branch, it's just more of a general question that I was wondering
about.

Thanks,
Chris

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