【python手写算法】numpy实现简易神经网络和反向传播算法【1】

import numpy as np

def dense(A,W):
    Z=np.matmul(A,W)#矩阵乘法
    return 1/(1+np.exp(-Z))

if __name__ == '__main__':
    leanring_rate=100
    A=np.array([[200.0,17.0]])
    # W=np.array([[1,-3,5],
    #             [-2,4,-6]])
    # b=np.array([[-1,1,2]])
    W1 = np.array([[0., -10, 4],
                  [-1,3,2]])
    W2=np.array([[1.0],
                 [2],
                 [3]])
    b1=np.array([[-1,0,2.0]])
    b2 = np.array([[1.0]])
    hid=dense(A,W1)
    o=dense(hid,W2)
    for i in range(200):
        # 计算梯度
        o_error=1-o
        o_delta=(1-o)*o*(1-o)
        hid_error=o_delta.dot(W2.T)#这里W2转置之后才能对应上
        hid_delta=hid_error*(1-hid)*hid # 注意区分*和dot,*是向量点乘，dot是矩阵乘法，得到一个1乘3的delta数组
        print(o_error)
        # 更新模型参数
        W1+=A.T.dot(hid_delta)*leanring_rate
        W2+=hid.T.dot(o_delta)*leanring_rate
        #前向传播
        hid = dense(A, W1)
        o = dense(hid, W2)

    print(W1,"\n")
    print(hid,W2,"\n")
    print(o)
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找了好多资料，勉强搭建起自己的简易神经网络，后面估计是基于这个的优化。
这里相当于简化了没使用偏置
参考文章：
https://blog.csdn.net/jining11/article/details/88678065?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522169478897716800182747019%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=169478897716800182747019&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduend~default-1-88678065-null-null.142^v94chatsearchT3_1&utm_term=%E7%94%A8numpy%E5%AE%9E%E7%8E%B0%E7%A5%9E%E7%BB%8F%E7%BD%91%E7%BB%9C&spm=1018.2226.3001.4187
https://www.cnblogs.com/jsfantasy/p/12177275.html