When to use Fixed Point these days

Question

For intense number-crunching i\'m considering using fixed point instead of floating point. Of course it\'ll matter how many bytes the fixed point type is in size, on what CPU i

Answer 1

Its nearly ALWAYS faster to use fixed point (experience of x86, pentium, 68k and ARM). It can, though, also depend on the application type. For graphics programming (one of my main uses of fixed point) I've been able to optimize the code using prebuilt cosine tables, log tables etc. But also the basic mathematical operations have also proven faster.

A comment on financial software. It was said in an earlier answer that fixed point is useful for financial calculations. In my own experience (development of large treasury management system and extensive experience of credit card processing) I would NOT use fixed point. You will have rounding errors using either floating or fixed point. We always use whole amounts to represent monetary amounts, counting the minimum amount possible (1c for Euro or dollar). This ensure no partial amounts are ever lost. When doing complex calculations values are converted to doubles, application specific rounding rules are applied and results are converted back to whole numbers.