# Julia 1.0 Example of @distributed and pmap

**URL:** <https://discourse.julialang.org/t/julia-1-0-example-of-distributed-and-pmap/14064>\
**Category:** Julia at Scale\
**Created:** [August 26, 2018, 2:53am UTC](https://discourse.julialang.org/t/julia-1-0-example-of-distributed-and-pmap/14064 "2018-08-26T02:53:05Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![iwelch](https://avatars.discourse-cdn.com/v4/letter/i/8c91f0/32.png) [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Post date:** [August 26, 2018, 2:53am UTC](https://discourse.julialang.org/t/julia-1-0-example-of-distributed-and-pmap/14064/1 "2018-08-26T02:53:05Z")

</div>

I am unable to get @distributed (aka @parallel) to work, even with a trivial example. I get errors. is it obvious what I am doing wrong?

```julia
$ julia
               _
   _ _ _(_)_ | Documentation: https://docs.julialang.org
  (_) | (_) (_) |
   _ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` | |
  | | |_| | | | (_| | | Version 1.0.0 (2018-08-08)
 _/ |\ __'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |

julia> using Distributed

julia> @everywhere testrun()= 0

julia> @sync @distributed for i=1:100; testrun(); end
Task (done) @0x000000011d410fd0

julia> addprocs(3)
3-element Array{Int64,1}:
 2
 3
 4

julia> @sync @distributed for i=1:100; testrun(); end
ERROR: On worker 4:
UndefVarError: #testrun not defined
deserialize_datatype at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:1051
handle_deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:743
deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:703
handle_deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:750
deserialize_global_from_main at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:703
#5 at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/clusterserialize.jl:72 [inlined]
foreach at ./abstractarray.jl:1835
deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/clusterserialize.jl:72
handle_deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:797
deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:703
handle_deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:747
deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:703
deserialize_datatype at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:1075
handle_deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:743
deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:703
handle_deserialize at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:750
deserialize_msg at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:703
#invokelatest#1 at ./essentials.jl:686 [inlined]
invokelatest at ./essentials.jl:685 [inlined]
message_handler_loop at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:160
process_tcp_streams at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:117
#105 at ./task.jl:259
#remotecall_fetch#149(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Distributed.Worker, ::Distributed.RRID, ::Vararg{Any,N} where N) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:379
remotecall_fetch(::Function, ::Distributed.Worker, ::Distributed.RRID, ::Vararg{Any,N} where N) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:371
#remotecall_fetch#152(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Int64, ::Distributed.RRID, ::Vararg{Any,N} where N) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:392
remotecall_fetch at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:392 [inlined]
call_on_owner at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:465 [inlined]
wait(::Future) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:486
sync_end(::Array{Any,1}) at ./task.jl:213
macro expansion at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/macros.jl:268 [inlined]
(::getfield(Distributed, Symbol("##169#171")){getfield(Main, Symbol("##7#8")),UnitRange{Int64}})() at ./task.jl:244
Stacktrace:
 [1] sync_end(::Array{Any,1}) at ./task.jl:226
 [2] top-level scope at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Distributed/src/macros.jl:337
 [3] top-level scope at task.jl:244

```

`pmap()` seems to have similar errors. but has the `@everywhere` not sent off the function to the worker processes?

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<div class="post-metadata">

**Author:** ![adamslc](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/adamslc/32/3452_2.png) [@adamslc](https://discourse.julialang.org/u/adamslc)\
**Post date:** [August 26, 2018, 2:56am UTC](https://discourse.julialang.org/t/julia-1-0-example-of-distributed-and-pmap/14064/2 "2018-08-26T02:56:14Z")

</div>

Your issue is that `@everywhere` defines `testrun` on _every process that is currently running_, but processes that are added later do not have `testrun` defined. If you `addprocs(3)` before you define `testrun` (or start julia with `julia -p3`), then it should work.