Behaviour of enumerate   in parallel  12712 Closed nilshg opened this Issue on Aug 20, 2015 · 3 comments Projects None yet Labels parallel Milestone No milestone Assignees No one assigned 5 participants  nilshg  elextr  ivarne  jakebolewski  kshyatt Notifications    nilshg nilshg commented on Aug 20, 2015  I first brought this up in the julia users group here:  julia  list     a ,  b ,  c          for i in enumerate list           println i         end   1, a    2, b    3, c    But:  julia  addprocs 2           parallel for i in enumerate list           println i         end  ERROR: `getindex` has no method matching getindex ::Enumerate Array ASCIIString,1  , ::UnitRange Int64    As  Ismael-VC pointed out in the user group, it works in parallel with  julia   parallel for i in collect enumerate list                     println i         end  But it seems a bit confusing to me that the behaviour of enumerate   changes depending on whether the loop is run in parallel or not.  kshyatt kshyatt added the parallel label on Aug 20, 2015  ivarne ivarne referenced this issue on Aug 20, 2015 Closed add support for `enumerate` with starting index  12713  elextr elextr commented on Aug 21, 2015  I would assume that  parallel needs to pass subsets of the enumeration to the separate processes, but iterators don't support any form of slicing or indexing so it is unable to and fails.  The error message could be clearer though.  Or if it can detect an iterator then  parallel could do the collect itself.  ivarne ivarne commented on Aug 21, 2015  Another solution would be to have a new function partition_paralell a::AbstractArray, n::Int , that return an array of roughly equal length iterables that can be serialized and distributed to workers. Relying on getindex and linear indexing with ranges has some disadvantages with non-array types.  jakebolewski The Julia Language member jakebolewski commented on Aug 26, 2015  Duplicate of  10435. To make this more generic, we can implement a variety of leader follower iterators popularized by ZPL and more recently Chapel. This is basically what  ivarne is describing.  jakebolewski jakebolewski closed this on Aug 26, 2015  malmaud malmaud referenced this issue on Oct 14, 2015 Open  parallel and zip    10435