## RE: [Algorithms] EPA : working ?

 RE: [Algorithms] EPA : working ? From: Hamilton Feltman - 2004-04-30 20:37:00 ```But thats not what I asked. with y=3D1, x*y !=3D 1 and with y=3D0, x*y !=3D 0 you said the order matters so we can assume: x*y !=3D y*x the question: is x*y =3D=3D x*y? i.e. is it really *random*, or deterministic depending on value? > -----Original Message----- > From: gdalgorithms-list-admin@... > [mailto:gdalgorithms-list-admin@...]On Behalf Of Tom > Forsyth > Sent: Thursday, April 29, 2004 11:16 PM > To: gdalgorithms-list@... > Subject: RE: [Algorithms] EPA : working ? >=20 >=20 > x*1 is not necessarily x, and x*0 is not necessarily 0. The=20 > bottom bit of > the mantissa is pretty random. >=20 > Perversely, 1*x IS always x, and 0*x IS always 0. So the=20 > order matters. > (er... it may be the other way around - I forget - not that=20 > you can usually > control the order when coding in C). >=20 > And to answer your question - it's true of all FP=20 > calculations on the whole > machine, since the EE FP unit _is_ a VU pipe. >=20 > TomF. >=20 > > -----Original Message----- > > From: gdalgorithms-list-admin@...=20 > > [mailto:gdalgorithms-list-admin@...] On=20 > > Behalf Of Chapman, Greg > > Sent: 29 April 2004 12:07 > > To: gdalgorithms-list@... > > Subject: RE: [Algorithms] EPA : working ? > >=20 > >=20 > > Just some vector unit fun -- there's an error of one bit, so a value > > multiplied by one is not promised to be the same value.=20 > There are some > > easy workarounds, though. > >=20 > > It causes all sorts of fun while track bugs if you're not=20 > aware of the > > problem while writing your microcode. > >=20 > > -----Original Message----- > >=20 > > Are you saying that the ps2 comes up with different results for the > > exact same computation? On which processor, the ee or the=20 > vu's? I'd be > > interested to know if this algorithm fails on that platform. >=20 >=20 >=20 >=20 >=20 > ------------------------------------------------------- > This SF.Net email is sponsored by: Oracle 10g > Get certified on the hottest thing ever to hit the market...=20 > Oracle 10g.=20 > Take an Oracle 10g class now, and we'll give you the exam FREE. > http://ads.osdn.com/?ad_id=3D3149&alloc_id=3D8166&op=3Dclick > _______________________________________________ > GDAlgorithms-list mailing list > GDAlgorithms-list@... > https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list > Archives: > http://sourceforge.net/mailarchive/forum.php?forum_id=3D6188 >=20 >=20 ```