Oh, let me answer my own question 2. I did not realize I had not given types to phat and vector in type ML. Sanity restored! I still can't find the answer to question 1 though.
On Wednesday, October 7, 2015 at 4:25:00 PM UTC-4, Patrick Kofod Mogensen wrote: > > So I asked a question over at > https://github.com/lindahua/Devectorize.jl/issues/48#issuecomment-146307811 > and it seems that I have got something completely wrong. > > It seems that the following > > index = rand(8000) > phat = zeros(8000) > > phat = 1./(1+exp(-index)) > > binds the output of the calculation on the rhs to a _new_ vector phat, not > the original vector. This really means I have misunderstood > preallocation/re-using memory in Julia completely! @blakejohnson suggests > that I use > > phat[:] = 1./1+(exp(-index)) > > instead. As this puts the calculations in the already preallocated vector > phat. > > Question 1) Can I learn more about this in the documentation ? I'm having > a hard time finding anything, probably because [:] is hard to use as a > search phrase, and I'm not sure what concepts to search for. > > > > I often wrap my variables in a type, but this seems like an extremely bad > idea in combination with devec. I have taken Blake Johnsons examples from > github, and added a few > https://gist.github.com/pkofod/fb6c4b8ffcca1a056363 > > Question 2) What is it that makes test4() and test6() run so slowly? > test1() and test3() seems to perform equivalently fast. I use this kind of > setup all the time, and I am surprised that this method allocates so much > memory. > > Bad news: I've been doing Julia ALL wrong! > Good news: Time to learn some more! >
