How am I supposed to use pmap?

General Usage
12

Do you have a minimal example?

I typically use this approach:

  1. Put everything you need distributed to workers into a Module.
  2. Save Module to filesystem
  3. Ensure path to Module is in LOAD_PATH
  4. addprocs()
  5. using Module

Notes:

  • It is important to addprocs before using Module
  • You shouldn’t need @everywhere
  • You shouldn’t get warnings about replacing module.

Here’s an example:

module ModuleA
    export testA
    function testA(x)
        println(x, " -> ", x*x)
        return x*x
    end
end

Save this to file ModuleA.jl (or ModuleA/src/ModuleA.jl)

Now run this:

addprocs()

# ensure module is in LOAD_PATH
# in this example, module A was saved to working directory (but can be any directory)
thisDir = dirname(@__FILE__())
any(path -> path == thisDir, LOAD_PATH) || push!(LOAD_PATH, thisDir)

using ModuleA

pmap(testA, 1:10)

And here’s the output:

Julia-0.5.2> include("loading_pmap.jl")
        From worker 2:  1 -> 1
        From worker 3:  4 -> 16
        From worker 5:  2 -> 4
        From worker 4:  3 -> 9
        From worker 2:  5 -> 25
        From worker 5:  6 -> 36
        From worker 4:  7 -> 49
        From worker 3:  8 -> 64
        From worker 2:  9 -> 81
        From worker 4:  10 -> 100
10-element Array{Any,1}:
   1
   4
   9
  16
  25
  36
  49
  64
  81
 100
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