Re: Non-deterministic numerical inaccuracies in
- To: mathgroup at smc.vnet.net
- Subject: [mg94965] Re: Non-deterministic numerical inaccuracies in
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Thu, 1 Jan 2009 07:26:41 -0500 (EST)
- References: <gjfjuo$dan$1@smc.vnet.net>
Bob Hanlon wrote: > $Version > > 7.0 for Mac OS X x86 (64-bit) (November 11, 2008) > > No problem apparent. > > > Bob Hanlon > > > On Tue, Dec 30, 2008 at 12:26 PM , Sjoerd C. de Vries wrote: > I think I might be able to guess what this is connected with. 64-bit C will use the XMM registers for floating point. These are 64-bits in length. 32-bit C has to cater for much older hardware, and so will use the old coprocessor registers. These are 80-bits in length. If the kernel contains some code that saves these registers as 64-bit numbers - say in response to a random interupt - this will truncate the extra bits when they are restored and make a tiny change in certain circumstances. It would be interesting if someone at WRI would tell me if I have guessed correctly! David Bailey http://www.dbaileyconsultancy.co.uk