If it won't be simple, it simply won't be. [Hire me, source code] by Miki Tebeka, CEO, 353Solutions

Friday, January 04, 2008

Faster and Shorter "dot" using itertools

Let's calculate the dot product of two vectors:

from itertools import starmap, izip
from operator import mul

def dot1(v1, v2):
result = 0
for i, value in enumerate(v1):
result += value * v2[i]
return result

def dot2(v1, v2):
return sum(starmap(mul, izip(v1, v2)))

if __name__ == "__main__":
from timeit import Timer

num_times = 1000
v1 = range(100)
v2 = range(100)

t1 = Timer("dot1(%s, %s)" % (v1, v2), "from __main__ import dot1")
print t1.timeit(num_times) # 0.038722038269

t2 = Timer("dot2(%s, %s)" % (v1, v2), "from __main__ import dot2")
print t2.timeit(num_times) # 0.0260770320892
dot2 is faster and shorter, however dot1 is more readable - my vote goes to dot2.

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