Re: [sage-devel] Re: algdep (PARI) with clang on FreeBSD
On 30/03/2017 11:33, Thierry wrote: Hi, On Thu, Mar 30, 2017 at 10:20:21AM +0200, Marc Mezzarobba wrote: Thierry wrote: I do not remember where i read that (correct me if i am wrong, or provide a reference if you know where it is), but RDF is supposed to round towards the nearest floating-point number. RR is, but I think RDF may or may not provide correct rounding depending what the underlying libm does. I found the reference i was looking for : http://doc.sagemath.org/html/en/reference/rings_numerical/sage/rings/real_double.html#sage.rings.real_double.RealDoubleElement.ulp So, if this depends on libm, i guess this should be updated and we should provide a way to know/modify the current rounding mode ? You can obtain and modify the CPU rounding mode using the C functions declared in fenv.h int FE_TONEAREST int FE_UPWARD int FE_DOWNWARD int FE_TOWARDZERO int fegetround () int fesetround (int) (there is an example in src/sage/graphs/base/static_sparse_graph.pyx) However, this go beyond libm and will affect any library using floating point numbers. Vincent -- 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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
Re: [sage-devel] Re: algdep (PARI) with clang on FreeBSD
Hi, On Thu, Mar 30, 2017 at 10:20:21AM +0200, Marc Mezzarobba wrote: > Thierry wrote: > > I do not remember where i read that (correct me if i am wrong, or > > provide a reference if you know where it is), but RDF is supposed to > > round towards the nearest floating-point number. > > RR is, but I think RDF may or may not provide correct rounding depending > what the underlying libm does. I found the reference i was looking for : http://doc.sagemath.org/html/en/reference/rings_numerical/sage/rings/real_double.html#sage.rings.real_double.RealDoubleElement.ulp So, if this depends on libm, i guess this should be updated and we should provide a way to know/modify the current rounding mode ? Ciao, Thierry > -- > Marc > > -- > 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 https://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. -- 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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
[sage-devel] Re: algdep (PARI) with clang on FreeBSD
Thierry wrote: > I do not remember where i read that (correct me if i am wrong, or > provide a reference if you know where it is), but RDF is supposed to > round towards the nearest floating-point number. RR is, but I think RDF may or may not provide correct rounding depending what the underlying libm does. -- Marc -- 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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
