Re: Possible loss of accuracy

[Sergei Steshenko]

--- On Wed, 5/15/13, Marco Caliari <address@hidden> wrote:

> From: Marco Caliari <address@hidden>
> Subject: Re: Possible loss of accuracy
> To: "Jordi Gutiérrez Hermoso" <address@hidden>
> Cc: address@hidden
> Date: Wednesday, May 15, 2013, 11:34 PM
> On Wed, 15 May 2013, Jordi Gutiérrez
> Hermoso wrote:
> 
> > On 15 May 2013 10:27, Jordi Gutiérrez Hermoso <address@hidden>
> wrote:
> >> I believed older versions of gcc turned on or off
> -ffloat-store at
> >> some optimisation levels, but I don't think newer
> versions affect
> >> -ffloat-store anymore.
> > 
> > I'd be curious to see the output for the following bash
> snippet with
> > your version of gcc:
> > 
> > for i in 0 1 2 3; do echo "O$i"; gcc -Q -O$i
> --help=optimizers | grep
> > store; done
> 
> O0
>   -ffloat-store         
>            
>    [disabled]
>   -ftree-store-ccp         
>             [disabled]
> O1
>   -ffloat-store         
>            
>    [disabled]
>   -ftree-store-ccp         
>             [disabled]
> O2
>   -ffloat-store         
>            
>    [disabled]
>   -ftree-store-ccp         
>             [enabled]
> O3
>   -ffloat-store         
>            
>    [disabled]
>   -ftree-store-ccp         
>             [enabled]
> 
> I confirm that the trick exp(2^50*log(1-2^-50)) works. What
> should I try next, a newer gcc compiler or a newer glibc (I
> have 2.6.1 installed)? Or both?
> 
> Thanks,
> 
> Marco
> 
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I suggest new glibc - which in practice means newer version of your Linux 
distro, which means newer version of gcc :-).

Regards,
  Sergei.