[英]How to vectorize the following python code?
我正在嘗試使用Numpy和矢量化操作來使代碼段運行得更快,但我沒有成功找到解決方案。 如果有人有想法......謝謝。
這是帶循環的工作代碼:
y = np.zeros(len(tab))
for i in range(len(tab)):
s = 0
for n in range(len(coef[0])):
s += coef[0][n] * ((a + b * np.dot(tab[i], vectors[n])) ** d)
y[i] = s
哪里,
您可以使用基於np.einsum
的方法和使用np.einsum
matrix-multiplication with np.dot
如下所示 -
# Calculate "((a + b * np.dot(tab[i], vectors[n])) ** d)" part
p1 = (a + b*np.einsum('ij,kj->ki',tab,vectors))**d
# Include "+= coef[0][n] *" part to get the final output
y_vectorized = np.dot(coef,p1)
運行時測試
數據集#1:
這是一個快速運行時測試,將原始循環方法與針對某些隨機值的建議方法進行比較 -
In [168]: N = 50
...: M = 50
...: P = 50
...:
...: tab = np.random.rand(N,M)
...: vectors = np.random.rand(P,M)
...: coef = np.random.rand(1,P)
...:
...: a = 3.233
...: b = 0.4343
...: c = 2.0483
...: d = 3
...:
In [169]: %timeit original_approach(tab,vectors,coef,a,b,c,d)
100 loops, best of 3: 4.18 ms per loop
In [170]: %timeit proposed_approach(tab,vectors,coef,a,b,c,d)
10000 loops, best of 3: 136 µs per loop
數據集#2:
N
, M
和P
為150
,運行時間為 -
In [196]: %timeit original_approach(tab,vectors,coef,a,b,c,d)
10 loops, best of 3: 37.9 ms per loop
In [197]: %timeit proposed_approach(tab,vectors,coef,a,b,c,d)
1000 loops, best of 3: 1.91 ms per loop
看起來很糟糕。 但這是你需要的嗎?
y = array([ sum( [coef[0][n] * ((a + b * np.dot(tab[i], vectors[n])) ** d)
for n in range(len(vectors[0]))] ) for i in range(len(tab)) ])
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