The new SubArrays steal mercilessly from the good ideas of both the old SubArray and ArrayViews, and then add some new tricks of their own. In theory, they should be a strict improvement on both of their predecessors.
--Tim On Friday, December 05, 2014 05:13:28 AM David van Leeuwen wrote: > So what is the relation between ArrayViews and 0.4 `SubArray revamp'? Are > they targeting different use cases or is one of them going to be phased > out? > > On Friday, December 5, 2014 1:28:16 PM UTC+1, Tim Holy wrote: > > In 0.4, the views are a revamp of SubArray. So if NamedArrays already > > interacts well with SubArrays, you're basically set. > > > > Most likely not, as SubArrays are new to me (I've tried sub() in > > production code in the past, but it was always better to write out a > loop)). > > > FYI the implementation in 0.4 is largely backwards-compatible, but there > > are > > some important differences. If you need to dig into the internal > > implementation > > of SubArrays, you can find documentation on the changes for 0.4 here: > > http://docs.julialang.org/en/latest/devdocs/subarrays/ > > > > OK, I'll have to study this in order to understand the implications for > > NamedArrays. > > ---david > > > --Tim > > > > On Friday, December 05, 2014 04:18:08 AM David van Leeuwen wrote: > > > Hi, > > > > > > On Friday, December 5, 2014 8:47:22 AM UTC+1, Ján Dolinský wrote: > > > > Hi, > > > > > > > > I am exploring DataFrames and NamedArrays packages and I would like to > > > > ask > > > > > > whether their are suitable for heavier computations and whether I can > > > > use > > > > > > them directly in BLAS calls (e.g. gemv() etc.). In addition, is it > > > > possible > > > > to create views of e.g. DataFrames or NamedArrays ? > > > > > > > > I can only speak for NamedArrays. On the one hand the deployment of > > > > BLAS > > > > > should be transparant and the use of NamedArray vs Array not lead to > > > > much > > > > > degradation in performance. E.g., "a * b" with `a` and `b` a > > > > NamedArray, > > > > > effectively calls "a.array * b.array" which Base implements with > > > BLAS.gemm(). There is just a little overhead of filling in sensible > > > > names > > > > > in the result---so if you have small matrices in an inner loop, you're > > > going to get hurt. > > > > > > On the other hand, I am not sure how much of the Julia BLAS cleverness > > > > is > > > > > retained in NamedArrays---but the intention of the package is that it is > > > completely transparent, and if you notice bad performance for a > > > > particular > > > > > situation then you should file an issue (or make a PR:-). Individual > > > element indexing of a NamedArray with integers is just a little bit > > > > slower > > > > > than that of an Array. Indexing by name is quite a bit slower---you may > > > try a different Associative than the standard Dict. > > > > > > Incidentally, I've been toying with the idea of NamedArrays `*` check on > > > consistency of index and dimension names, but my guess is that people > > > > would > > > > > find such a thing annoying. > > > > > > ArrayViews are currently not aware of NameArrays. I believe the views > > > > are > > > > > going to be part ov julia-0.4, so then it would be a task for NamedArray > > > > to > > > > > implement views of NamedArrays I gather. > > > > > > Cheers, > > > > > > ---david > > > > > > > Thanks, > > > > Jan
