学习衰减率：
随着学习的进行，使得学习率逐渐减小。AdaGrad会为参数的每个元素适当的体哦阿正学习率
# coding： utf-8import numpy as npclass AdaGrad: def __init__(self, learning_rate=0.01): self.learning_rate = learning_rate self.h = None def update(self, params, grads): if self.h is None: self.h = {} for key, value in params.items(): self.h[key] = np.zeros_like(value) for key in params.keys(): self.h[key] += grads[key] * grads[key] params[key] -= self.learning_rate * grads[key] / (np.sqrt(self.h[key]) + 1e-07) # 1e-07微小值避免分母为0