Re: [Mingw-users] MinGW and Floating Point

[KHMan <kei...@gm...>]

Richard C. Wagner wrote:
> Kein-Hong and Ben:
> Looking at the user's manual for the programming language of the second 
> test, I see that the calculations were made using the PC's "80-bit, 
> extended real" format.  I believe that means that the mantissa is kept 
> as an 80-bit number. [snip]

Nope, and at this point I'd recommend an hour or two of Googling 
and Wikipedia-ing on floating point number formats thereabouts. :-)

> [snip]
> which are pretty much identical to the third column.  So in this test 
> case, it was just a difference in the precision of the calculations.  In 
> my Mandelbrot program, I actually rewrote it to use doubles, rather than 
> floats, and I didn't see much difference.  Perhaps I did something 
> wrong, or perhaps it only makes a small difference.  Regardless, mystery 
> solved. Thanks for your help.

doubles give another 29 bits of precision, about 9 decimal digits. 
You'd zoom in much more in the high-dwell areas. It's a big 
difference -- floats won't work at all at high zooms! You need 
doubles or better at high zooms. On most x86 CPUs today, I don't 
think floats is any faster than doubles, so you might as well 
stick to doubles.

You should also try compiling for SSE2/3, I suspect there is a 
speed boost lurking in there somewhere...

-- 
Cheers,
Kein-Hong Man (esq.)
Kuala Lumpur, Malaysia