[SciPy-user] filling array without loop...
fred
fredmfp@gmail....
Sun Apr 22 11:31:51 CDT 2007
Hi,
I try to fix the following problem, using scipy arrays method.
The fact is that I don't know which methods I can use to fix it.
Thus, I set this array, with loops, as this :
cells_array = array([[VTK_HEXAHEDRON_NB_POINTS, \
k*(nx*ny) + j*nx + i, \
k*(nx*ny) + j*nx + i+1, \
k*(nx*ny) + (j+1)*nx + i+1, \
k*(nx*ny) + (j+1)*nx + i, \
(k+1)*(nx*ny) + j*nx + i, \
(k+1)*(nx*ny) + j*nx + i+1, \
(k+1)*(nx*ny) + (j+1)*nx + i+1, \
(k+1)*(nx*ny) + (j+1)*nx + i] \
for k in range(nz-1) for j in
range(ny-1) for i in range(nx-1)], dtype='i').ravel()
Works fine, but a bit too slow for nx,ny,nz \approx 10^2 (endless).
As an example, let's say nx, ny, nz = 2, 3, 4 ; cells_array looks like this:
[[ 8 0 1 3 2 6 7 9 8]
[ 8 2 3 5 4 8 9 11 10]
[ 8 6 7 9 8 12 13 15 14]
[ 8 8 9 11 10 14 15 17 16]
[ 8 12 13 15 14 18 19 21 20]
[ 8 14 15 17 16 20 21 23 22]]
My first idea is to work on the transpose of the array:
[[ 8 8 8 8 8 8]
[ 0 2 6 8 12 14]
[ 1 3 7 9 13 15]
[ 3 5 9 11 15 17]
[ 2 4 8 10 14 16]
[ 6 8 12 14 18 20]
[ 7 9 13 15 19 21]
[ 9 11 15 17 21 23]
[ 8 10 14 16 20 22]]
My second idea is to proceed step-by-step.
1) Filling the first row is trivial.
2) Second row
I'm thinking of setting
a = arange(0, ny, 2) (set [0, 2])
then "replicate" a to the next items, adding (ny-1)*(nz-1) each time.
-> a = [ 0 2 6 8 12 14]
3) 3rd, 4th & 5th rows
a+1
a+3
a+2
4) 6th to 9th
repeat previous steps.
I think I have the idea (at least, one idea ;-)
but don't know how to do this with scipy.
Any suggestion are welcome.
Thanks in advance.
Cheers,
--
http://scipy.org/FredericPetit
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