#16424: is_triangular_number() speed up
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Reporter: rws | Owner:
Type: enhancement | Status: new
Priority: minor | Milestone: sage-6.3
Component: quadratic forms | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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The name implies a boolean return value (contrary to the implementation),
and used that way the function is way too slow:
{{{
sage: timeit('l=[n for n in range(1000) if is_square(8*(n)+1)]')
625 loops, best of 3: 909 µs per loop
sage: timeit('l=[n for n in range(1000) if is_triangular_number(n)]')
5 loops, best of 3: 200 ms per loop
sage: timeit('l=[n for n in range(1000) if is_square(8*(n)+1)]')
625 loops, best of 3: 903 µs per loop
sage: timeit('l=[n for n in range(1000) if is_triangular_number(n)]')
5 loops, best of 3: 195 ms per loop
}}}
The reason is that the simple boolean test used above is not performed
before the more involved computation of the index.
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Ticket URL: <http://trac.sagemath.org/ticket/16424>
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