Rahul wrote:
> I want to compute dot product of two vectors stored as lists a and b.a
> and b are of the same length.
>
> one simple way is
> sum(a[i]*b[i] for i in range(len(a)))
>
> another simple way is
> ans=0.0
> for i in range(len(a)):
> ans=ans+a[i]*b[i]
>
> But is there any other way which is faster than any of the above. (By
> the way profiling them i found that the second is faster by about 30%.)
You could try
sigma = 0
for ai, bi in itertools.izip(a, b):
sigma += ai * bi
or
sum(itertools.starmap(operator.mul, itertools.izip(a, b)))
but if you are really concerned about number-crunching efficiency, use
Numarray.
Peter
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