It is supported in SubArrays and you can also multiply with these in place with A_mul_B!, but this will be calling a generic multiplication method implemented in Julia instead of BLAS. So far it doesn't support the α and β arguments of C:=αAB+βC, but I'm working on that.
2015-03-29 18:23 GMT-04:00 Dominique Orban <[email protected]>: > Unfortunately, my idx will be computed on the fly and there's zero chance > that it would be a range. Is there a plan to support more general indexing > in subarrays and/or ArrayView? > > > On Sunday, March 29, 2015 at 6:13:16 PM UTC-4, Andreas Noack wrote: >> >> C[:,idx] creates a copy, so gemm updates a copy of part of C and then >> discarts it after the computation. sub(C,:,idx) creates a view instead of a >> copy. >> >> 2015-03-29 18:10 GMT-04:00 Dominique Orban <[email protected]>: >> >>> Sorry there was a typo in my example. It should have been >>> >>> BLAS.gemm!('N', 'N', 1.0, A[:,idx], B[idx,idx], 1.0, C[:,idx]); >>> >>> for the dimensions to work out. >>> >>> The gemm! command works fine, is happy with the dimensions, and produces >>> the correct update. As far as I can tell, >>> >>> C1 = C[:,idx]; >>> BLAS.gemm!('N', 'N', 1.0, A[:,idx], B[:,idx], 1.0, C1); >>> >>> does what it's supposed to do, it just doesn't update C (which is >>> awkward for a ! function, though I realize there's something else going on >>> here). >>> >>> >>> On Sunday, March 29, 2015 at 5:56:27 PM UTC-4, Andreas Noack wrote: >>>> >>>> I think that you could use sub(A,:,2:2:4) for BLAS, but not >>>> sub(A,:,[2,4]) because the indexing has to be with ranges for BLAS to be >>>> able to extract the right elements of the matrix. >>>> >>>> 2015-03-29 17:34 GMT-04:00 Dominique Orban <[email protected]>: >>>> >>>>> Sorry if this is another [:] kind of question, but I can't seem to >>>>> find the right syntax to call BLAS.gemm! on part of an array. The piece of >>>>> code >>>>> >>>>> julia> n = 10; m = 5; idx = [2, 4]; >>>>> julia> C = rand(n, m); A = rand(n, m); B = rand(m, m); >>>>> julia> BLAS.gemm!('N', 'N', 1.0, A[:,idx], B[:,idx], 1.0, C[:,idx]); >>>>> >>>>> won't modify C. I'm simply trying to do >>>>> >>>>> C[:,idx] += A[:,idx] * B[:,idx]; >>>>> >>>>> What's the right syntax here? >>>>> >>>>> It seems ArrayViews.jl might be the way to go, but it doesn't let me >>>>> do view(A, :, idx). >>>>> >>>>> Thanks! >>>>> >>>> >>>> >>
