convert mpf t to double with rounding-modes defined by ieee754

Décio Luiz Gazzoni Filho decio at
Mon Aug 1 10:40:12 CEST 2005

On Aug 1, 2005, at 5:29 AM, usenett at wrote:

>> Why not use mpfr_t throughout, without making any conversions?
>> Or are you implying that MPFR is inefficient?
> I don't want to say that MPFR is inefficient, I'm far away from  
> this view.
> But for my situation (simulating a long accumulator) I prefer GMP,  
> cause
> MPFR has a bigger functionality than I need and that makes it slow  
> for my
> purpose.

I don't see how bigger functionality and speed are related. Do you  
have actual numbers to back up your statement, or is this just an  
instance of the old `C++ is slow' mentality?

> The only advantage is the closing rouned double conversion.
> Of course later on a comparison between my implementation and MPFR  
> would be
> interesting.

I find it very hard to believe that you could do better than MPFR.  
It's not like the MPFR authors are some random web/VB code monkeys  
releasing a weekend project on Sourceforge.

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