import numpy
from chainer import cuda
from chainer import optimizer
[docs]class RMSprop(optimizer.GradientMethod):
"""Hinton's RMSprop."""
def __init__(self, lr=0.01, alpha=0.99, eps=1e-8):
self.lr = lr
self.alpha = alpha
self.eps = eps
def init_state(self, param, state):
xp = cuda.get_array_module(param.data)
with cuda.get_device_from_array(param.data):
state['ms'] = xp.zeros_like(param.data)
def update_one_cpu(self, param, state):
ms = state['ms']
grad = param.grad
ms *= self.alpha
ms += (1 - self.alpha) * grad * grad
param.data -= self.lr * grad / (numpy.sqrt(ms) + self.eps)
def update_one_gpu(self, param, state):
cuda.elementwise(
'T grad, T lr, T alpha, T eps',
'T param, T ms',
'''ms = alpha * ms + (1 - alpha) * grad * grad;
param -= lr * grad / (sqrt(ms) + eps);''',
'rmsprop')(param.grad, self.lr, self.alpha, self.eps,
param.data, state['ms'])