On Thu, 27 Aug 2009, Nils Bruin wrote: > > On Aug 27, 3:46 am, Jason Moxham <ja...@njkfrudils.plus.com> wrote: > >> the source arguments to the mpz_* functions are const pointers so the memory >> they point to will not change (thru that pointer) , ie as long as c does not >> alias a or b then GMP will not change a or b . The above code will work. > > Excellent. So that gives one safe approach with a small memcpy > penalty. > >> Logic is two-compliment on a stored sign-magnitude representation so the >> above >> does not hold. The chance that GMP wants more than above for say mpz_add is >> not zero , consider SSE or the new AVX extenstions if these become a big >> benefit , then we may round up to next largest 16bytes or whatever.I have one >> case where I may want to do this sort of round up , but I probably wont get >> around to trying it out for about a year. MPIR is optimized for the "common >> case" and I am hoping that this weird situation where we want to use two >> memory mangers is a one off. > > OK. Understandable. I don't think anybody would want MPIR to slow down > in order to satisfy certain exotic API demands. Once we have this > under way, I may just try if preallocating enough space to avoid the > temp speeds things up. > > If it's noticeable, perhaps it's an idea to export the way in which > mpz_add, mpz_sub (and perhaps a few other common routines) compute the > required number of limbs for their result as a macro? Preallocating > sufficient limbs probably can lead to speed-ups regardless of which > memory manager is used. In cases where it's complicated, one could > just leave it out.
You can use the mpn_* functions directly, which make explicit assumptions about buffer lengths. (Probably not worth the hassle though.) - Robert --~--~---------~--~----~------------~-------~--~----~ 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 URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
