On Tue, 29 Oct 2013, Vincent Delecroix wrote:
all rounding are implemented in the CPU (is that true ? perhaps changing the rounding often makes it slower). Do you have timings ?
Seems to be more complicated than just slow-or-fast -question. See http://www.intel.co.uk/content/dam/doc/manual/64-ia-32-architectures-optimization-manual.pdf pages 3-98..3-100:
"On the Pentium III processor, the FLDCW instruction is an expensive operation. On early generations of Pentium 4 processors, FLDCW is improved only for situations where an application alternates between two constant values of the x87 FPU control word (FCW), such as when performing conversions to integers. On Pentium M, Intel Core Solo, Intel Core Duo and Intel Core 2 Duo processors, FLDCW is improved over previous generations."
This manual contains even an example of algorithm that avoids changing rounding mode.
However, two rounding modes are enought for RIF. Or are they? -- Jori Mäntysalo -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
