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前言

在阅读Neural Networks Tutorial – A Pathway to Deep Learning4.1 A simple example in code小节的时候,其中的例子:

x_old = 0 # The value does not matter as long as abs(x_new - x_old) > precision
x_new = 6 # The algorithm starts at x=6
gamma = 0.01 # step size
precision = 0.00001

def df(x):
    y = 4 * x**3 - 9 * x**2
    return y

while abs(x_new - x_old) > precision:
    x_old = x_new
    x_new += -gamma * df(x_old)

print("The local minimum occurs at %f" % x_new)

这是典型的通过不断进行迭代,从而计算得到最值的方法;在algorithm领域这叫什么呢?以我的直觉来看,我暂时叫做它:iterative optimization algorithm;它有些贪心算法的意味;