Does Repa always use unboxed Vectors? But a Repa array can store any element, so how does it handles types which haven't an unboxed equivalent? Or is the unboxing done automatically?
2011/11/10 Bas van Dijk <v.dijk....@gmail.com> > On 9 November 2011 22:33, kaffeepause73 <kaffeepaus...@yahoo.de> wrote: > > Repa is indeed very Interesting, but I have changing vector length in the > > second dimension and later on only want to generate Data on demand. If I > use > > Matrices, I will use loads of space for no reason. > > Even if it is possible to create an unboxed vector of unboxed vectors, > if the inner unboxed vectors have variable lengths as you require, > indexing will become O(n) instead of O(1) because you need to traverse > the inner unboxed vectors and check their length to find the desired > index. I'm not sure that's what you want. > > > Seems like sticking to Boxed Vector for now is best Choice for me. > > Yes your second alternative: a boxed vector of unboxed vectors seems > to do what you want. > > > isn't data.vector also providing multidimensional arrays? > > I don't think so. All indexing functions get a single Int argument. Of > course it's easy to build a layer on top that adds more dimensions. > > > So is Repa just another Version of Data.Vector or is it building another > level on top. > > The latter, repa provides a layer on top of vector. > > Note that you can also convert Vectors to repa Arrays using: > > fromVector :: Shape sh => sh -> Vector a -> Array sh a > > I believe its O(1). > > > And when to use best which of the two ? > > I guess when your vectors are multi-dimensional and you want to > benefit from parallelism you should use repa instead of vector. > > Cheers, > > Bas > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
