numpy - 理解一维向量上的 np.matmul

Question

a = [1, 2, 3]
b = [10, 10, 10]

np.matmul(a, b) 结果是 60。

numpy 如何乘以 (3,) 和 (3,) 维度并返回点积而不是外积(3 * 3)或抛出错误“维度不匹配”？

Answer 1

这直接来自 numpy.matmul() 的文档:

• If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. After matrix multiplication the prepended 1 is removed.
• If the second argument is 1-D, it is promoted to a matrix by appending a 1 to its dimensions. After matrix multiplication the appended 1 is removed.

因此，输入的形状 a和 b转换为 (1, 3)和 (3,1)分别在矩阵乘法过程中。

根据矩阵乘法的规则，我们知道:
1 x 3 3 x 1 | |
-------- ===> 总结。

因此，我们将结果作为标量。