Adding "MaxDestroyerEvents" as a step spec to WolframModel (C++)

[daneelsan]

Changes

• Closes #611.
• Adds the "MaxDestroyerEvents" (per expression) to WolframModel as a step specification:

  WolframModel[{{1, 2}, {2, 3}} -> {{2, 3}, {2, 4}, {3, 4}, {2, 1}},
           {{1, 1}, {1, 1}},
           <|"MaxEvents" -> 5, "MaxDestroyerEvents" -> 2|>,
           "EventSelectionFunction" -> "MultiwaySpacelike"]

Comments

• This works as follows: The causal graph keeps track of how many destroyer events each expression has (expressionsIDsToDestroyerEventsCount_). During evolution, we check if the destroyer event count of an expression (causalGraph_.destroyerEventsCount(expressionID)) exceeds the maximum allowed (maxDestroyerEvents_), and if it does, we eliminate that expression and matches related to that expression from the matcher.

• Missing tests, both for C++ and WL.

• Missing documentation.

Examples

• Notice how "MaxDestroyerEvents" is not a stopping condition, but behaves similar to an event selection function:

  In[] := Table[
  WolframModel[
  {{1, 2}, {2, 3}} -> {{2, 3}, {2, 4}, {3, 4}, {2, 1}},
  {{1, 1}, {1, 1}},
  <|"MaxEvents" -> 5, "MaxDestroyerEvents" -> maxDestroyerEvents|>,
  "EventSelectionFunction" -> "MultiwaySpacelike"
  ]["ExpressionsEventsGraph", VertexLabels -> "Index"],
  {maxDestroyerEvents, {1, 2, Infinity}}] // GraphicsRow

• This is also supported for "EventSelectionFunction" -> None:

  In[] := Table[
  WolframModel[
  {{1, 2}, {2, 3}} -> {{2, 3}, {2, 4}, {3, 4}, {2, 1}},
  {{1, 1}, {1, 1}},
  <|"MaxEvents" -> 5, "MaxDestroyerEvents" -> maxDestroyerEvents|>,
  "EventSelectionFunction" -> None
  ]["ExpressionsEventsGraph", VertexLabels -> "Index"],
  {maxDestroyerEvents, {1, 2, 3, Infinity}}] // GraphicsRow

  

• "MaxDestroyerEvent" -> 1, for any "EventSelectionFunction", behaves effectively as a singleway system:

  In[] := Table[
  WolframModel[
  {{1, 2}, {2, 3}} -> {{2, 3}, {2, 4}, {3, 4}, {2, 1}},
  {{1, 1}, {1, 1}},
  <|"MaxEvents" -> 5, "MaxDestroyerEvents" -> 1|>,
  "EventSelectionFunction" -> esf
  ]["ExpressionsEventsGraph", VertexLabels -> "Index"],
  {esf, {"GlobalSpacelike", "MultiwaySpacelike", 
  None}}] // GraphicsRow

  

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This change is 

[daneelsan]

You are right. By the way, the compilation fails on Windows because of maxDestroyerEvents_ == std::numeric_limits<int64_t>::max(). I switched it to maxDestroyerEvents_ == static_cast<uint64_t>(std::numeric_limits<int64_t>::max()) and it still complaints that theres a type mismatch. How would you fix this?

Ignore this. Apparently I didn't push my changes.