Returning Multiple RemoteRefs Error  9457 Closed JaredCrean2 opened this Issue on Dec 24, 2014 · 3 comments Projects None yet Labels doc error handling parallel Milestone No milestone Assignees No one assigned 4 participants  JaredCrean2  vtjnash  malmaud  jakebolewski Notifications    JaredCrean2 JaredCrean2 commented on Dec 24, 2014  I found that returning multiple values using remotecall produces a  rather strange  error. Does anyone know why this would fail in parallel? Although there are a few workaround  using arrays and cell arrays , it would be very useful to be able to directly reuse functions that work in serial for parallel codes.  Here is the script file Script1-jl that triggers the error:    script to be executed on process 1   run with julia -p 1 . Script1-jl   everywhere include  funcs-jl    a   1 b   2  ret1   remotecall 2, func1, a, b  wait ret1   ret2, ret3   remotecall 2, func2, a, b            error wait ret2   and here is the function file funcs-jl:  function func1 c, d   println  c    , c  println  d    , d   return c  end   function func2 c, d   println  c    , c  println  d    , d   return c, d  end   Here is the error info:  ERROR: start has no method matching start ::RemoteRef  in include at . boot-jl:245 in include_from_node1 at loading-jl:128 in process_options at . client-jl:285 in _start at . client-jl:354 in _start_3B_1720 at  usr bin .. lib x86_64-linux-gnu julia sys.so while loading  home dev1 julia_tests ret_values Script1-jl, in expression starting on line 12  Julia version info Julia Version 0.3.3 Commit 21d5433   2014-10-21 20:18 UTC  Platform Info: System: Linux  x86_64-linux-gnu  CPU: Intel R  Core TM  i7-3770K CPU   3.50GHz WORD_SIZE: 64 BLAS: libopenblas  NO_LAPACK NO_LAPACKE DYNAMIC_ARCH NO_AFFINITY Nehalem  LAPACK: liblapack.so.3 LIBM: libopenlibm LLVM: libLLVM-3.3  vtjnash The Julia Language member vtjnash commented on Dec 25, 2014  remotecall always returns a single RemoteRef  help?  remotecall Base.remotecall id, func, args...      Call a function asynchronously on the given arguments on the    specified process. Returns a  RemoteRef .  the error message could perhaps be improved. it happens because of: a, b   RemoteRef   gets translated into an iterator over the right hand side  vtjnash vtjnash added error handling doc labels on Dec 25, 2014  jakebolewski jakebolewski added the parallel label on Jun 2, 2015  malmaud malmaud commented on Oct 14, 2015  This is kinda tricky. The docs for remotecall seems pretty clear and the very first section in the parallel computing manual chapter explains that remotecall returns a RemoteReference. But you do have to understand that returning multiple values just means returning a single tuple whose elements are the individual return values.   JaredCrean2, I'd be interesting in hearing your thoughts on what could make the documentation clearer.  JaredCrean2 JaredCrean2 commented on Oct 14, 2015  I didn't realize this issue was still open. I just tested with a more recent version of Julia and found if I change the script to:    script to be executed on process 1   run with julia -p 1 . Script1-jl   everywhere include  funcs-jl    a   1 b   2  ret1   remotecall 2, func1, a, b  wait ret1   ret2   remotecall 2, func2, a, b   wait ret2  a1,b2   fetch ret2     unpack the tuple here println  a1, b1    , a1,  ,  , b2   then everything works as expected. Returning a single RemoteRef pointing to a tuple seems like a reasonable way to of doing things combined with the documentation, so I'll close.  JaredCrean2 JaredCrean2 closed this on Oct 14, 2015