mpq_get_d() rounding for different platforms?

[Vincent Lefevre]

On 2009-03-17 14:41:02 -0700, K Shen wrote:
> I ran the same code on all systems:
> 
> main () {
>   double i, j, k;
>   mpq_t rat;
>  
>   printf("hi\n");
>   mpq_init(rat);
>   mpq_set_ui(rat, 4, 5);
>   k = mpq_get_d(rat);
>   printf("rat is %.17f\n", k);
>  
> }
> 
> and I built from the same GMP source. 

But if there are x86 machines, the different results can be due to
the extended precision. This can depend on the OS, on the compiler
(including its version) and on the compiler options.

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Vincent Lefèvre <vincent at vinc17.org> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)