Re: [Numpy-discussion] Lookup array

2011-10-11 Thread Andrey N. Sobolev 
В Mon, 10 Oct 2011 11:20:08 -0400
Olivier Delalleau sh...@keba.be пишет:

 
 The following doesn't use numpy but seems to be about 20x faster:
 
 A_rows = {}
 for i, row in enumerate(A):
 A_rows[tuple(row)] = i
 for i, row in enumerate(B):
 C[i] = A_rows.get(tuple(row), -1)
 
 -=- Olivier

Thanks a lot, Olivier, that's makes my program like 3x faster. 
One lesson I can draw from this - don't try to use NumPy in 
situations it doesn't fit :)

WBR,
Andrey


-- 
Researcher,
General and theoretical physics dept., South Ural State University
454080, Pr. Lenina, 76, Chelyabinsk, Russia
Tel: +7 351 265-47-13
and...@physics.susu.ac.ru
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[Numpy-discussion] Norm of array of vectors

2011-03-17 Thread Andrey N. Sobolev 
Dear all, 

Sorry if that's a noob question, but anyway. I have several thousands of
vectors stacked in 2d array. I'd like to get new array containing
Euclidean norms of these vectors and get the vector with minimal norm.

Is there more efficient way to do this than 
argmin(array([sqrt(dot(x,x)) for x in vec_array]))?

Thanks in advance.
Andrey.

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Re: [Numpy-discussion] Norm of array of vectors

2011-03-17 Thread Andrey N. Sobolev 
Hi eat and Gary,

Thanks a lot for your suggestions, I've tried them in my code and
achieved similar speedup of ~270% for both of them. So I guess I'll
stick to one of those. 

Regards,
Andrey. 


 Hi,
 
 On Thu, Mar 17, 2011 at 10:44 AM, Andrey N. Sobolev inco...@list.ru
 wrote:
 
  Dear all,
 
  Sorry if that's a noob question, but anyway. I have several
  thousands of vectors stacked in 2d array. I'd like to get new array
  containing Euclidean norms of these vectors and get the vector with
  minimal norm.
 
  Is there more efficient way to do this than
  argmin(array([sqrt(dot(x,x)) for x in vec_array]))?
 
 Try
 argmin(sum(vec_array** 2, 0)** 0.5)
 
 Regards,
 eat
 
 
  Thanks in advance.
  Andrey.
 
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