Numpy dot & multiply

np.dot

1.一维情况

import numpy as np
a1 = np.array([1,2,3])
a2 = np.array([2,3,4])
mul1 = np.dot(a1, a2)
print mul1

输出结果[20]， 即是计算:

a_{1} * a_{2}^{T}

2.二维情况

import numpy as np
a1 = np.reshape(np.arange(6), (2,3))
a2 = np.reshape(np.arange(6), (3,2))
mul2 = np.dot(a1, a2)
print mul2

输出结果为[[10, 13], [28, 40]]，即是计算:

a_1 * a_2

np.multiply

1.一维情况

import numpy as np
a1 = np.array([i+1 for i in range(6)])
a2 = np.array([i+3 for i in range(6)])
mul3 = np.multiply(a1, a2)
print mul3

输出结果为[3, 8, 15, 24, 35, 48]， 即是计算(对应数相乘):

[a1_0 * a2_0, ... , a1_5 * a2_5]

2. 二维情况

import numpy as np
a1 = np.reshape(np.array([i+1 for i in range(6)]), (2,3))
a2 = np.reshape(np.array([i+3 for i in range(6)]), (2,3))
mul4 = np.multiply(a1, a2)
print mul4

输出结果为:[[3, 8, 15], [24, 35, 48]]，计算方式同上。