From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gabriel Dos Reis To: Theodore Papadopoulo Cc: Gabriel Dos Reis , dewar@gnat.com, amylaar@redhat.com, aoliva@redhat.com, gcc@gcc.gnu.org, moshier@moshier.ne.mediaone.net, torvalds@transmeta.com, tprince@computer.org Subject: Re: What is acceptable for -ffast-math? (Was: associative law in combine) Date: Wed, 01 Aug 2001 11:44:00 -0000 Message-id: References: <200108011821.f71IL3d09937@mururoa.inria.fr> X-SW-Source: 2001-08/msg00087.html Theodore Papadopoulo writes: | [1 ] | | | gdr@codesourcery.com said: | > No, I do mean a transformation which does not dramatically transmute | > the computations. | | That's not a definition. Do you have one? Changing 0.125 to 0.0 is a dramatic change. | Dramatically, can mean very different things | depending on the people and on the algorithms. That's basically the | point that I'm trying to make. In many applications and algorithm | the optimization a/b/c to a/(b*c) is meaningful and relevant. In the case I showed, I was tring to compute a unit-length vector by first scaling in order to avoid overflow (the /c part). I'm not dismissing the fact that there are algorithms which would benefit from optimizations. As I said earlier, I'm a fervent proponent of optimizations. Not transformations which change the computation in a very unexpected ways. -- Gaby