/** Calculates the accumulated PRE value shifts for all updates on the list. */
private void accumulatePreValueShifts() {
if (!dirty) return;
int s = 0;
for (int i = updStructural.size() - 1; i >= 0; i--) {
final BasicUpdate t = updStructural.get(i);
s += t.shifts;
t.accumulatedShifts = s;
}
dirty = false;
}
