[Numpy-discussion] cross product of two 3xn arrays
oliphant.travis at ieee.org
Fri Feb 17 11:25:59 CST 2006
Charles R Harris wrote:
>On 2/17/06, Bill Baxter <wbaxter at gmail.com> wrote:
>>For folks using quats to represent rotations (which is all I use them for,
>>anyway), if you're batch transforming a bunch of vectors by one quaternion,
>>it's a lot more efficient to convert the quat to a 3x3 matrix first and
>>transform using matrix multiply (9 mults per transform that way vs 21 or so
>>depending on the implementation of q*v*q^-1). Given that, I can't see many
>>situations when I'd need a super speedy C version of quaternion multiply.
>On a related note, indexing in numarray is some 3x faster than in
>NumPy and I'm wondering what needs to be done to speed that up.
Please explain with a benchmark. This is not true for all indexing
operations. But, it is possible that certain use cases are faster.
We can't do anything without knowing what you are talking about exactly.
More information about the Numpy-discussion