[RFC] Quad-float support, round 4

[Tim Prince]

  On 9/13/2010 6:51 PM, Steve Kargl wrote:
> On Mon, Sep 13, 2010 at 08:17:56PM +0200, FX wrote:
>> (Yeah, Intel compiler doesn't like real(kind=10)...)
>>
>> Again, comparing __float128 to double:
>> SQRT is slower by 160, SIN is slower by only 6, COS by 10,
>> ASINH by merely 10 and ERFC by 6 again. I'm actually amazed
>> at how it does that!
>>
> First, I agree that worrying about performance at this point
> should not be a priority.  Perhaps, someone like Tim Prince
> might step forward to lend a hand in optimizing the code.
>
>
I haven't figured out yet where you did this in the source code, nor 
what ground rules you are applying.
If you have decided to use an iterative improvement for sqrt(), the 
native x87 sqrt in 64-bit precision mode followed by a single Heron's 
step should be sufficient.  I don't think people would normally change 
precision mode when running under cygwin, but there's no guarantee.

-- 
Tim Prince