For the FFT the aliasing is not so important, as the butterfly can be done into temporary space then swapped. I use this strategy a lot and it doesn't affect the FFT timings.
Bill On 31 December 2011 18:22, Jason <[email protected]> wrote: > On Saturday 31 December 2011 17:47:03 Jason wrote: >> On Tuesday 27 December 2011 17:27:48 Bill Hart wrote: >> > In my FFT I make use of mpn_sumdiff_n and mpn_addsub_n. It seems these >> > are not exported even though there are generic C versions. >> > >> > Also, I see there is no sumdiff_n.as on core2 style machines. Is it >> > possible to include mpn_sumdiff_n.c in the library on such machines so >> > that it is included unconditionally for all machines? >> > >> >> we would still have the other arches to do ie power,arm etc ,to make it >> unconditional addsub needs to allocate some tmp space ,I suppose we could >> split the addsub it to various overlap cases this may be possible , but for >> sumdiff I dont think it is >> > > addsub is possible , and so is addadd although the case addadd_n(t,x,y,z) > where t=x=y=z requires mul_1(t,x,3) which on core2 and sandybridge the same > speed as two adds , dont know about the other arch ,although if we consider > this a rare case then it may not be important. sumdiff the only difficult > case is when the sum and difference are aliased with the bot the sources , we > could exclude this overlap condition? , it would also relax the instruction > ordering which would ease up finding faster asm versions > > >> > Is there a reason to not have an assembly optimised version for core2? >> > >> >> I havent found one for core2 or sandybridge which is faster than a separate >> add and sub >> >> > Bill. >> > >> > >> >> > > -- > You received this message because you are subscribed to the Google Groups > "mpir-devel" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/mpir-devel?hl=en. > -- You received this message because you are subscribed to the Google Groups "mpir-devel" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/mpir-devel?hl=en.
