Benchmarks - LDC vs GDC

[Cecil Ward]

On Tuesday, 27 June 2023 at 19:58:57 UTC, Walter Bright wrote:
> Be leery of using fastmath switches unless you are very 
> knowledgeable about fp math and how fastmath changes it.
>
> DMD doesn't have a fastmath switch for good reason.

Walter, your warning is appreciated. I read some of the GCC 
documentation, but I’ve no intention of going near the fast math 
thing in a production program as indeed I haven’t thought it 
through enough.

Since DMD doesn’t have such a thing, then fast-math needs to be 
banned in benchmarks that include DMD otherwise it’s not a level 
playing field.

Isn’t the main thing ignoring infinities and NaNs? I don’t think 
that’s all there is to it though. I would say, in my extremely 
limited exposure to floating point, that if you have debugged 
your code then infinities and NaNs should not be encountered 
anyway unless you have possible special cases to deal with 
relating to input that you’re not in control of.