[fpc-pascal] Floating point question

[Michael Van Canneyt]

On Tue, 13 Feb 2024, James Richters via fpc-pascal wrote:

> Sorry for the kind of duplicate post, I submitted it yesterday morning and I
> thought it failed, so I re-did it and tried again.. then after that the
> original one showed up.
>
> A thought occurred to me.   Since the complier math is expecting all the
> constants would be in full precision, then the compiler math doesn't need to
> change, it's just that the reduction in precision is just happening too
> soon.  It's evaluating and reducing each term of an expression, then the
> math is happening, and the answer is not coming out right.
>
> If instead everything was left full precision until after the compiler math
> (because this is what the compiler math expects), and then the final answer
> was reduced in precision where possible, then it would work flawlessly.  So
> the reduction in precision function only needs to run once on the final
> answer, not on every term before the calculation.

As Jonas said, this would result in less efficient code, since all the math 
will then be done at full precision, which is slower.

As usual, it is a trade-off between size (=precision) and speed.

Michael.