05_CartPole-reinforcement-learning_PER_D3QN

SumTree_update.py

def update(self, tree_index, priority):
    # Change = new priority score - former priority score
    change = priority - self.tree[tree_index]
    self.tree[tree_index] = priority

    # then propagate the change through tree
    # this method is faster than the recursive loop
    while tree_index != 0:
        tree_index = (tree_index - 1) // 2
        self.tree[tree_index] += change