我正在尝试为Keras(link)实现弹性反向传播优化程序,但是具有挑战性的部分是能够根据每个参数的相应梯度是否为正值来执行更新,负数或零。我编写了下面的代码作为实现Rprop优化器的开始。但是,我似乎无法找到单独访问参数的方法。循环遍历params
(如下面的代码所示)在每次迭代时返回p, g, g_old, s, wChangeOld
,它们都是矩阵。Keras - 执行Rprop算法的问题
有没有一种方法可以迭代各个参数并更新它们?如果我可以根据其渐变的符号对参数向量进行索引,它也可以工作。谢谢!
class Rprop(Optimizer):
def __init__(self, init_step=0.01, **kwargs):
super(Rprop, self).__init__(**kwargs)
self.init_step = K.variable(init_step, name='init_step')
self.iterations = K.variable(0., name='iterations')
self.posStep = 1.2
self.negStep = 0.5
self.minStep = 1e-6
self.maxStep = 50.
def get_updates(self, params, constraints, loss):
grads = self.get_gradients(loss, params)
self.updates = [K.update_add(self.iterations, 1)]
shapes = [K.get_variable_shape(p) for p in params]
stepList = [K.ones(shape)*self.init_step for shape in shapes]
wChangeOldList = [K.zeros(shape) for shape in shapes]
grads_old = [K.zeros(shape) for shape in shapes]
self.weights = stepList + grads_old + wChangeOldList
self.updates = []
for p, g, g_old, s, wChangeOld in zip(params, grads, grads_old,
stepList, wChangeOldList):
change = K.sign(g * g_old)
if change > 0:
s_new = K.minimum(s * self.posStep, self.maxStep)
wChange = s_new * K.sign(g)
g_new = g
elif change < 0:
s_new = K.maximum(s * self.posStep, self.maxStep)
wChange = - wChangeOld
g_new = 0
else:
s_new = s
wChange = s_new * K.sign(g)
g_new = p
self.updates.append(K.update(g_old, g_new))
self.updates.append(K.update(wChangeOld, wChange))
self.updates.append(K.update(s, s_new))
new_p = p - wChange
# Apply constraints
if p in constraints:
c = constraints[p]
new_p = c(new_p)
self.updates.append(K.update(p, new_p))
return self.updates
def get_config(self):
config = {'init_step': float(K.get_value(self.init_step))}
base_config = super(Rprop, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
你不需要K.switch(K.equal(其他城市,0),......),而不是在这里,如果/ elif的/别的吗? – gkcn