#16295: Faster is_orthogonal_array
-------------------------+-------------------------------------------------
Reporter: | Owner:
ncohen | Status: needs_review
Type: | Milestone: sage-6.3
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
combinatorics | Work issues:
Keywords: | Commit:
Authors: | b9f8b0388a8cd333bfaf4160896b09be5550896a
Nathann Cohen | Stopgaps:
Report Upstream: N/A |
Branch: |
u/ncohen/16295 |
Dependencies: |
#16236 |
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Comment (by leif):
Replying to [comment:32 ncohen]:
> `times_n2` ? What for ?
It's used twice, in the outer loop and the first inner loop:
{{{
#!python
for i in range(k): # For any column C1
C1 = OAc+i*n2
for j in range(i+1,k): # For any column C2 > C1
C2 = OAc+j*n2
...
}}}
One would usually not look up multiples of `n^2` (or `n` in the earlier
case), but do
{{{
#!python
C1 = OAc
i = 0
while i < k:
... # similar for C2, j
C1 += n2
i++
}}}
In C, you'd presumably drop `j` (and perhaps also `i`) altogether, and
just compare the pointers to the address of the (current sub-)array end.
(And inlining the bitset operations would of course make it even faster.
Afterwards special-case for `n`=2^m^ ... :-) )
--
Ticket URL: <http://trac.sagemath.org/ticket/16295#comment:35>
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