New Issue: Expose targetLocales indices to the user?

17915, "vasslitvinov", "Expose targetLocales indices to the user?", "2021-06-14T13:21:14Z"

Background: Currently distributions like Block store the locales that the indices are to be distributed over in an array targetLocales. "Local descriptor" classes (in DSI slang) are stored in arrays of the same shape as targetLocales. When some computation needs to access a local descriptor, it needs to perform a translation from here to the index into targetLocales. This happens, for example, for queries like localSubdomains(). This may be complicated because there may be multiple indices into targetLocales in the case of oversubscription.

This issue proposes to expose the indices into targetLocales to the user, for example via an iterator. This will enable:

  • easy handling of certain operations in the case of oversubscriptions,
  • determining the locale that is the left/right/... neighbor for the current computation.