updateGlobalLearnError method
Publishes the epoch's learn error, rolling the previous value.
Used by native-accelerated trainers (which run the epoch off-loop) so that
the learning-rate/momentum strategies adapt identically to the pure-Dart
path. The pure-Dart learn sets these fields directly and does not call
this method.
Implementation
void updateGlobalLearnError(double globalLearnError) {
_lastGlobalLearnError = _globalLearnError;
_globalLearnError = globalLearnError;
}