Re: Possible loss of accuracy

[Marco Caliari]

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