mirror of
https://github.com/Farama-Foundation/Gymnasium.git
synced 2025-08-16 03:38:44 +00:00
44 lines
1.6 KiB
Python
44 lines
1.6 KiB
Python
|
"""Utility functions for the wrappers."""
|
||
|
|
import numpy as np
|
||
|
|
|
||
|
|
|
||
|
|
class RunningMeanStd:
|
||
|
|
"""Tracks the mean, variance and count of values."""
|
||
|
|
|
||
|
|
# https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Parallel_algorithm
|
||
|
|
def __init__(self, epsilon=1e-4, shape=()):
|
||
|
|
"""Tracks the mean, variance and count of values."""
|
||
|
|
self.mean = np.zeros(shape, "float64")
|
||
|
|
self.var = np.ones(shape, "float64")
|
||
|
|
self.count = epsilon
|
||
|
|
|
||
|
|
def update(self, x):
|
||
|
|
"""Updates the mean, var and count from a batch of samples."""
|
||
|
|
batch_mean = np.mean(x, axis=0)
|
||
|
|
batch_var = np.var(x, axis=0)
|
||
|
|
batch_count = x.shape[0]
|
||
|
|
self.update_from_moments(batch_mean, batch_var, batch_count)
|
||
|
|
|
||
|
|
def update_from_moments(self, batch_mean, batch_var, batch_count):
|
||
|
|
"""Updates from batch mean, variance and count moments."""
|
||
|
|
self.mean, self.var, self.count = update_mean_var_count_from_moments(
|
||
|
|
self.mean, self.var, self.count, batch_mean, batch_var, batch_count
|
||
|
|
)
|
||
|
|
|
||
|
|
|
||
|
|
def update_mean_var_count_from_moments(
|
||
|
|
mean, var, count, batch_mean, batch_var, batch_count
|
||
|
|
):
|
||
|
|
"""Updates the mean, var and count using the previous mean, var, count and batch values."""
|
||
|
|
delta = batch_mean - mean
|
||
|
|
tot_count = count + batch_count
|
||
|
|
|
||
|
|
new_mean = mean + delta * batch_count / tot_count
|
||
|
|
m_a = var * count
|
||
|
|
m_b = batch_var * batch_count
|
||
|
|
M2 = m_a + m_b + np.square(delta) * count * batch_count / tot_count
|
||
|
|
new_var = M2 / tot_count
|
||
|
|
new_count = tot_count
|
||
|
|
|
||
|
|
return new_mean, new_var, new_count
|