Re: gcc compiler option -Ofast used when compiling Ruby implementation (using C code) maybe gives bugs?

Colin Bartlett wrote:
> I've been looking at ways of making the Date class faster, mostly
> by replacing its use of floating point arithmetic by faster integer
> arithmetic, but also in some cases by changing the algorithms.

Cool :-)

> On each platform I tried using different optimization options. Using
> -O0, -O1, -O2, -O3, -Og, -Os the results were the same for the current
> Date C functions and my versions.
>
> But when I used -Ofast then for some functions I was getting different
> results from the current Date C functions and my versions.

That could be normal for -Ofast:

-Ofast: Disregard strict standards compliance... also enables
optimizations that are not valid for all standard-compliant
programs... turns on -ffast-math.

-ffast-math: ... can result in incorrect output for programs that
depend on an exact implementation... It may, however, yield faster
code for programs that do not require the guarantees of these
specifications.



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