Re: Is real(16) available on x86 platforms?

[Erik Schnetter <schnetter at cct dot lsu dot edu>]

On Jan 14, 2007, at 10:16:12, Dominique Dhumieres wrote:

> > Your question is sort of wrong.
>
> OK! Is 128-bit floating point type supported on AMD64
> running the FX's x86_64-unknown-linux-gnu?
>
> More precisely, I was trying to test a piece of code using
> real(16) executing (not working) on a G5 under OSX 10.3 (PPC)
> on an AMD64 box under linux where I got the error.
>
> I was a bit surprised because as far as a know real(16) floats
> are not supported by the G5 hardware, but a some software
> emulation (gmp/mpfr?). I was just expecting the same for AMD64,
> why shouldn't it be?

I think real(16) is implemented on PPC by combining two real(8)  
numbers suitably.  That is slower than a hardware-supported  
implementation, but gives you the accuracy.

This is not available under Linux.  You can use real(10) there if you  
can live with the reduced accuracy.  Depending on your programme, you  
may need to specify -m128bit-long-double to use the same memory  
layout as real(16).

-erik

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Erik Schnetter <schnetter@cct.lsu.edu>

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