PERにて weights が更新されない

下記のサンプルスクリプトのように、addするときにpriorities=1e-4、更にupdate_priotiriesするときに同様の値で設定するが、weightsが1のままで更新されない。

import numpy as np

from cpprb.experimental import PrioritizedReplayBuffer


def make_replay_buffer(dim_state, dim_action):
    rb_dict = {
        "size": int(1e6),
        "default_dtype": np.float32,
        "env_dict": {
            "obs": {
                "shape": (dim_state,)},
            "next_obs": {
                "shape": (dim_state,)},
            "act": {
                "shape": (dim_action,)},
            "rew": {},
            "done": {}}}
    return PrioritizedReplayBuffer(**rb_dict)


dim_state = 10
dim_action = 3
buf = make_replay_buffer(dim_state, dim_action)

batch_size = 4

obses = np.zeros((batch_size, dim_state), dtype=np.float32)
next_obses = np.copy(obses)
actions = np.ones(shape=(batch_size, dim_action))
dones = np.zeros(shape=(batch_size,), dtype=np.float32)
rews = np.zeros(shape=(batch_size,), dtype=np.float32)
priorities = np.zeros(shape=(batch_size,), dtype=np.float32) + 1e-4

buf.add(
    obs=obses, act=actions, rew=rews, next_obs=next_obses,
    done=dones, priorities=priorities)

samples = buf.sample(batch_size)
print(samples["weights"])

buf.update_priorities(samples["indexes"], priorities)
samples = buf.sample(batch_size)
print(samples["weights"])