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Greetings! Just confirmed this on intel as well. Amazing! I don't
know why I hadn't thought of it before. Definitely the way to go.
Peter Strazdins <firstname.lastname@example.org> writes:
> Hi Clint,
> probably this is well-known, but for Sparc, gcc -O compiles a call to
> the standard maths function fabs() as a fabss instruction (this works
> for single or double precision). Nothing could be easier :).
> The latest Solaris compilers (f95 at least) will convert the conditional
> ( (x) >= 0.0 ? (x) : -(x) ) to an fabss too.
> Regards, Peter
> eg. #define ATL_dabs(x) fabs(x)
> >> From email@example.com Sun May 13 03:32:06 2001
> >> My guess is that there are system-dependant ways to make fabs() one cycle
> >> nonetheless, and I'm hoping some of you know or can easily discover them.
> >> Anyway, I want to ask anyone who can figure out to do fabs() without an if
> >> to post to the list. The solution can be as nonportable as you want;
> >> I figure in-line assembler may be required, but hopefully it can be used
> >> with a C macro. Here's an example macro for double precision:
> >> #define ATL_dabs(x) ( (x) >= 0.0 ? (x) : -(x) )
> >> If anyone can do it without the if, I think we can speedup quite a few
> >> routines . . .
> >> Any pointers appreciated,
> >> Clint
Camm Maguire firstname.lastname@example.org
"The earth is but one country, and mankind its citizens." -- Baha'u'llah
- Re: abs()
- From: Peter Strazdins <email@example.com>