bool Recurrence::calcIteratedUpdate(const UpdateMap &oldUpdate, const Expression &meterfunc, UpdateMap &newUpdate) {
assert(newUpdate.empty());
UpdateMap update = oldUpdate; //might be changed by dependencyOrder, so copy here
vector<VariableIndex> order = dependencyOrder(update);
assert(order.size() == update.size());
//in the given order try to solve the recurrence for every updated variable
for (VariableIndex vi : order) {
Expression res;
ExprSymbol target = itrs.getGinacSymbol(vi);
//use update rhs, but replace already processed variables with their recurrences
Expression todo = update.at(vi).subs(knownPreRecurrences);
if (!findUpdateRecurrence(todo,target,res)) {
return false;
}
//remember this recurrence to replace vi in the updates depending on vi
//note that updates need the value at n-1, e.g. x(n) = x(n-1) + vi(n-1) for the update x=x+vi
knownPreRecurrences[target] = res.subs(ginacN == ginacN-1);
//calcuate the final update using the loop's runtime
newUpdate[vi] = res.subs(ginacN == meterfunc);
}
return true;
}
