Re: fixed point vs floating point

[Stephen Leake <stephen_leake@stephe-leake.org>]

"RasikaSrinivasan@gmail.com" <rasikasrinivasan@gmail.com> writes:

> friends
>
> I am investigating the applicability of fixed point to a numerical
> problem. I would like to develop the algorithm as a generic and test
> with different floating and fixed point types to decide which one to
> go with.

What sort of criteria are you using to make the decision?

If it's just speed, then the answer will depend more on the hardware and
the level of compiler optimization than on this choice.

The major algorithmic difference between fixed and floating is the
handling of small differences; floating point allows arbitrarily small
differences (down to the exponent limit, of course), while fixed point
has a fixed small difference.

So the choice should be determined by the application, not by
experiment.

The only place I have found fixed point to be useful is for time;
everything else ends up needing to be scaled, so it might as well be
floating point from the beginning.

The other thing that can determine the choice is the hardware; if you
have no floating point hardware, you will most likely need fixed point.
But even then, it depends on your speed requirement. You can do floating
point in software; it's just slower than fixed point on the same hardware.

> - can we design a generic (function or procedure) that can accept
> either fixed point or floating point data types at the same time
> excluding other types

No.

-- 
-- Stephe