Consider a symbol in System such as CircleDot. I want to redefine this symbol and distribute the definition to subkernel, to use with ParallelEvaluate or the likes.

With a standard symbol in Global I can simply do

foo[___] := 1;
Print @ DownValues @ foo
ParallelEvaluate[Print @ DownValues @ foo];

which will show that the definition is automatically distributed to subkernels.

However, doing the same with CircleDot doesn't work:

enter image description here

Using DistributeDefinitions@CircleDot doesn't seem to change this. Why does this happen?

I know I can force subkernels to accept the definition by directly doing something like ParallelEvaluate[CircleDot[___]:=1], but this might not be desirable in some cases, and also I would like to understand why some symbols seem to behave different in this context.

  • $\begingroup$ Does this answer your question? How are function definitions distributed to parallel kernels? $\endgroup$
    – Szabolcs
    Commented Sep 14, 2021 at 19:32
  • $\begingroup$ See also mathematica.stackexchange.com/a/128287/12 $\endgroup$
    – Szabolcs
    Commented Sep 14, 2021 at 19:32
  • $\begingroup$ @Szabolcs thanks, hadn't seen those. So a possible solution is changing $DistributedContexts. This is however in this case not desirable, as far as I can tell, as we don't want to let the whole of System` distribute. Is there a way to have DistributeDefinitions work on a specific function in System` ? The solution given in the linked post, DistributeDefinitions[const`precisionRate], doesn't seem to work in this case: DistributeDefinitions[System`CircleDot] doesn't do what it should $\endgroup$
    – glS
    Commented Sep 14, 2021 at 19:41
  • 2
    $\begingroup$ In trying to find an automatic way to identify the symbols that need to be redefined in each parallel kernel, I find it weird that Language`ExtendedFullDefinition[System`CircleDot]is an empty definition list, even after being defined. In contrast, Definition[CircleDot] and Information[CircleDot, "Definitions"] shows the user definition. Thought i'd mention it. $\endgroup$
    – thorimur
    Commented Sep 14, 2021 at 22:24
  • 1
    $\begingroup$ @thorimur to see the definition list you have to use Language`ExtendedFullDefinition[CircleDot, "ExcludedContexts" -> {}] (see my answer below) $\endgroup$
    – Hausdorff
    Commented Nov 26, 2021 at 14:30

1 Answer 1


Some spelunking of DistributeDefinitions shows that all contexts listed in Parallel`Protected`$ExcludedContexts are by default excluded from being distributed. In particular, Parallel`Protected`DistDefs has the line

updates = ExtendedFullDefinition[expr, "ExcludedContexts"->$ExcludedContexts]

So to make sure that new definitions of symbols in System` are also distributed you can use something like



ParallelEvaluate[Print @ DownValues @ CircleDot];

This way we also only distribute new definitions for CircleDot and nothing else in System`.

Regarding the comment of @thorimur: you do not get the full definition of CircleDot from Language`ExtendedFullDefinition, as the default option "ExcludedContexts"->Automatic seems to filter System` as well. So by setting this option yourself you can also see the full definition

Language`ExtendedFullDefinition[CircleDot, "ExcludedContexts" -> {}]

Language`DefinitionList[HoldForm[CircleDot] -> {OwnValues -> {}, SubValues -> {}, UpValues -> {}, DownValues -> {HoldPattern[CircleDot[___]] :> 1}, NValues -> {}, FormatValues -> {}, DefaultValues -> {}, Messages -> {}, 
Attributes -> {}}, HoldForm[BlankNullSequence] -> {OwnValues -> {}, SubValues -> {}, UpValues -> {}, DownValues -> {}, 
NValues -> {}, FormatValues -> {}, DefaultValues -> {}, Messages -> {}, Attributes -> {Protected}}, HoldForm[Rule] -> {OwnValues -> {}, SubValues -> {}, UpValues -> {}, DownValues -> {}, NValues -> {}, FormatValues -> {}, 
DefaultValues -> {}, Messages -> {HoldPattern[Rule::rhs] -> "Pattern `1` appears on the right-hand side of rule `2`."}, 
Attributes -> {Protected, SequenceHold}}, HoldForm[List] -> {OwnValues -> {}, SubValues -> {}, UpValues -> {}, DownValues -> {}, 
NValues -> {}, FormatValues -> {}, DefaultValues -> {}, Messages -> {}, Attributes -> {Locked, Protected}}]

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