Since version 3.11 of Arcane, there is an automatic mechanism that allows comparing variable values before and after a synchronization. This allows one to know if a synchronization is useful or not.

Note: Currently, this mechanism only works for simple synchronizations (those called via the MeshVariableRef::synchronize() method.

To activate this mode, you must set the environment variable ARCANE_AUTO_COMPARE_SYNCHRONIZE. The three possible values are:

1 : to activate the mechanism and display at the end of the calculation for each variable the number of synchronizations that modified the ghost cell values.
2 : like 1 but additionally there is a listing printout at the time of synchronization if the synchronization did not modify any values (which suggests that it is potentially not useful).
3 : like 2 but additionally the call stack at the time of synchronization is displayed.

Note that modes 2 and 3 require performing a reduction for each synchronization, which can impact performance.

Bit-by-bit Comparison Unit Test Support in Arcane