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I have a function in the following form:

function[...] := With[
  {...},
  Table[
    anotherfunction[i, j, ...],
    {i, ...},
    {j, ...},
    ...
  ]
]

If I'd like to replace Table with ParallelTable, do I need to put DistributeDefinitions["Global`"] somewhere? If yes, where? (Before With, before ParallelTable, or before calling function?)

anotherfunction is defined globally, and uses other global variables.

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I added the backtick. Click the edit link and see the source on how to do it (you need to surround the code with $n+1$ backticks if you want to include $n$ backticks). –  Szabolcs Dec 20 '13 at 18:07
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1 Answer

up vote 4 down vote accepted

ParallelTable will automatically distribute the definitions of symbols used in the body of the table, as well as any dependencies, in version 8 and later. It is not necessary to use DistributeDefinitions with ParallelTable in these versions.

Note that ParallelEvaluate does not automatically distribute definitions like Parallelize, ParallelTable, ParallelMap, ParallelDo, etc. do. You do need to use DistributeDefinitions if you rely on ParallelEvaluate, however, you do not need to distribute the definitions of all symbols. Just distribute the symbol that you are actually using, anotherfunction in this case. DistributeDefinitions is smart enough to auto-distribute all the dependencies as well (unless you do something unusual such as converting strings to symbol names).

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+1. Also note from the documentation: "DistributeDefinitions applies itself recursively to any symbols appearing in the definitions of the symbols s_i." –  Andreas Lauschke Dec 20 '13 at 21:21
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