python broadcast广播

1.算法流程

Inputs: array A with m dimensions; array B with n dimensions
p = max(m, n) #p为A和B的维度较大的一个
if m < p:#填充维度
    left-pad A's shape with 1s until it also has p dimensions #在A的维度的左边填充1
else if n < p:
    left-pad B's shape with 1s until is also has p dimensions #在B的维度的左边填充1
result_dims = new list with p elements
for i in p-1 ... 0:#从最后一个维度开始检查 ，
    A_dim_i = A.shape[i]
    B_dim_i = B.shape[i]
    if A_dim_i != 1 and B_dim_i != 1 and A_dim_i != B_dim_i:#不符合广播条件
        raise ValueError("could not broadcast")
    else:
        result_dims[i] = max(A_dim_i, B_dim_i)

 

 2.两种情况

1.数组维度不同，后缘维度的轴长相符

2.数组维度相同，其中有个轴为1

https://www.cnblogs.com/jiaxin359/p/9021726.html