On 2010-08-21 07:55, Carl Witty wrote: > On Fri, Aug 20, 2010 at 9:26 PM, Dr. David Kirkby > <david.kir...@onetel.net> wrote: >> Unless OS X rounds by default to 64-bits, I can't understand how this would >> have ever worked. Why was it not necessary to change the rounding behavior >> of an Intel based OS X system? > > Modern x86 family chips actually have two totally separate > floating-point units (at least logically, I don't know if they share > hardware). The older uses the "x87" instructions, dating back to the > 8087; this rounds to 80 bits by default. SYMPOW's fpu.c changes the > x87 instructions to round to 64 bits. The newer is the SSE/SSE2 > floating-point unit (SSE only had single-precision floating point, > SSE2 extended this to double precision); this rounds to 64 bits (or 32 > bits for single-precision instructions).
gcc uses SSE by default on 64-bit Intel systems and FPU by default on 32-bit Intel systems. However, this can be changed with gcc's -mfpmath option: you can choose -mfpmath=387 or -mfpmath=sse -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
