I've opened an issue (https://github.com/JuliaLang/julia/issues/17593) - and realized that with Julia v0.5 we may not need this at all. :-)
On Saturday, July 23, 2016 at 8:47:57 PM UTC+2, Stefan Karpinski wrote: > > I would file an issue about having and fma! function. Since it's only > sensible for matrices (as far as I can tell), there doesn't seem to be a > corresponding need for muladd! since the fusion is at the collection level. > > On Sat, Jul 23, 2016 at 2:31 PM, Oliver Schulz <oliver...@tu-dortmund.de > <javascript:>> wrote: > >> Oh, sure - I was actually mainly thinking about matrices. I was looking >> for something like fma! in ArrayFire (without success), and then wondered >> what it might be called in Base. >> >> On Saturday, July 23, 2016 at 8:04:31 PM UTC+2, Stefan Karpinski wrote: >>> >>> They don't make sense for scalars but they could be added for matrices. >>> >>> On Sat, Jul 23, 2016 at 1:54 PM, Oliver Schulz <oliver...@tu-dortmund.de >>> > wrote: >>> >>>> Hi Stefan, >>>> >>>> sorry, yes, I had somehow overlooked fma. Mainly I was looking for an >>>> in-place version though, like fma! and muladd!. Is there a reason those >>>> don't exist? >>>> >>>> On Saturday, July 23, 2016 at 7:50:30 PM UTC+2, Stefan Karpinski wrote: >>>>> >>>>> Yes: https://github.com/JuliaLang/julia/issues/6330. In short, there >>>>> are both fma and muladd operations with different purposes: >>>>> >>>>> help?> fma >>>>> >>>>> >>>>> >>>>> search: fma findmax @fastmath UniformScaling >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> fma(x, y, z) >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> Computes x*y+z without rounding the intermediate result x*y. On some >>>>> systems this is significantly more expensive than x*y+z. fma is used to >>>>> improve accuracy in certain algorithms. See muladd. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> help?> muladd >>>>> >>>>> >>>>> >>>>> search: muladd >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> muladd(x, y, z) >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> Combined multiply-add, computes x*y+z in an efficient manner. This >>>>> may on some systems be equivalent to x*y+z, or to fma(x,y,z). muladd is >>>>> used to improve performance. See fma. >>>>> >>>>> On Sat, Jul 23, 2016 at 1:40 PM, Oliver Schulz < >>>>> oliver...@tu-dortmund.de> wrote: >>>>> >>>>>> Does Julia have a standardized FMA (Fused-Multiply-Add) function? >>>>>> Like fma(A, B, factor) and fma!(dest, A, B, factor), so that that GPU >>>>>> libraries, etc. can provide optimized versions? >>>>>> >>>>> >>>>> >>> >
