#6118: [with second patch, needs review] integer shifting slow
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Reporter: robertwb | Owner: somebody
Type: defect | Status: new
Priority: major | Milestone: sage-4.0.1
Component: basic arithmetic | Keywords:
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Comment(by robertwb):
Here's after just the first patch:
{{{
sage: a = 5; b = 6; c = 6r
sage: %timeit a << b
10000000 loops, best of 3: 195 ns per loop
sage: %timeit a >> b
1000000 loops, best of 3: 218 ns per loop
sage: %timeit a << c
10000000 loops, best of 3: 188 ns per loop
sage: %timeit a >> c
1000000 loops, best of 3: 217 ns per loop
sage: b = -6; c = -6r
sage: %timeit a << b
1000000 loops, best of 3: 204 ns per loop
sage: %timeit a >> b
10000000 loops, best of 3: 196 ns per loop
sage: %timeit a >> c
10000000 loops, best of 3: 190 ns per loop
sage: %timeit a << c
1000000 loops, best of 3: 222 ns per loop
}}}
and after the second patch
{{{
sage: sage: a = 5; b = 6; c = 6r
sage: sage: %timeit a << b
1000000 loops, best of 3: 192 ns per loop
sage: sage: %timeit a >> b
1000000 loops, best of 3: 204 ns per loop
sage: sage: %timeit a << c
1000000 loops, best of 3: 203 ns per loop
sage: sage: %timeit a >> c
1000000 loops, best of 3: 217 ns per loop
sage:
sage: sage: b = -6; c = -6r
sage: sage: %timeit a << b
1000000 loops, best of 3: 206 ns per loop
sage: sage: %timeit a >> b
1000000 loops, best of 3: 197 ns per loop
sage: sage: %timeit a >> c
1000000 loops, best of 3: 203 ns per loop
sage: sage: %timeit a << c
1000000 loops, best of 3: 222 ns per loop
}}}
With repeated timings, the variance seems to be about 5 or so ns. The only
significant differences are that Integer >> Integer is a bit faster with
the second patch, and Integer << int and Integer >> int are faster with
the first.
I'm (pleasantly) surprised making it a cpdef function didn't slow it down.
I don't think {{{shift_helper}}} needs to do error checking, and it seems
odd to introduce a new auxiliary variable {{{normalize_Integer}}}.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6118#comment:6>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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