private int randomPreviousState(
DuoBaumLevel level, int nodeAB1, int nodeA2, int nodeB2, double nodeValue) {
double d = random.nextDouble() * nodeValue;
double sum = 0.0;
for (int j = 0, n = level.size(); j < n; ++j) {
if (nodeAB1 == level.childNodeAB1(j)
&& nodeA2 == level.childNodeA2(j)
&& nodeB2 == level.childNodeB2(j)) {
sum += level.forwardValue(j);
if (d <= sum) {
return j;
}
}
}
return level.size() - 1; // error in finite bit arithmetic encountered
}
