[英]Difference between scipy.stats.norm.pdf and plotting gaussian manually
[英]Performance difference between scipy and numpy norm
我一直认为scipy.linalg.norm()
和numpy.linalg.norm()
是等价的(用于不接受轴参数的scipy版本,但现在它确实如此)。 然而,以下简单的例子会产生显着不同的表现:背后的原因是什么?
In [1]: from scipy.linalg import norm as normsp
In [2]: from numpy.linalg import norm as normnp
In [3]: import numpy as np
In [4]: a = np.random.random(size=(1000, 2000))
In [5]: %timeit normsp(a)
The slowest run took 5.69 times longer than the fastest. This could mean that an intermediate result is being cached.
100 loops, best of 3: 2.85 ms per loop
In [6]: %timeit normnp(a)
The slowest run took 6.39 times longer than the fastest. This could mean that an intermediate result is being cached.
1000 loops, best of 3: 558 µs per loop
scipy版本是0.18.1,numpy是1.11.1
查看源代码显示scipy
有自己的norm
函数,它包含numpy.linalg.norm
或BLAS函数,该函数速度较慢但更好地处理浮点溢出(请参阅有关此PR的讨论)。
但是,在你给出它的例子中看起来并不像SciPy使用BLAS函数,所以我认为它不会对你看到的时差造成影响。 但在调用numpy版本的规范之前,scipy会做一些其他的检查。 特别是,无限检查a = np.asarray_chkfinite(a)
是导致性能差异的可疑因素:
In [103]: %timeit normsp(a)
100 loops, best of 3: 5.1 ms per loop
In [104]: %timeit normnp(a)
1000 loops, best of 3: 744 µs per loop
In [105]: %timeit np.asarray_chkfinite(a)
100 loops, best of 3: 4.13 ms per loop
所以看起来np.asarray_chkfinite
大致说明了评估规范所花费的时间差。
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