On Aug 14, 12:59 am, Jonathan Bober <[EMAIL PROTECTED]> wrote: > This is exactly what NTL does in its quad float class. Just about every > function starts and ends with a macro to adjust the fpu, resulting in > around 7 extra assembly instructions. In the following code, the > overhead is quite significant - it takes around 21 seconds to execute on > my machine, but only about 4 seconds without the START_FIX and END_FIX. > Of course, this is not necessarily any sort of accurate test, but it > does indicate that this can be an expensive operation.
Yes, changing the floating-point modes is very slow on many (all?) x86 processors. I believe it flushes the floating-point pipeline, which takes many clock cycles. Carl --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
