Opened 10 years ago
Closed 15 months ago
#5091 closed defect (wontfix)
find_root should call fast_float
Reported by: | robertwb | Owned by: | burcin |
---|---|---|---|
Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |
Component: | calculus | Keywords: | |
Cc: | jason | Merged in: | |
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description
sage: f(x) = sin(x)-cos(x) sage: g = f._fast_float_() sage: timeit("find_root(f, 0, pi)") 625 loops, best of 3: 154 µs per loop sage: timeit("find_root(g, 0, pi)") 625 loops, best of 3: 24 µs per loop
See also http://groups.google.com/group/sage-devel/browse_thread/thread/927319a4fa61ae3b/9fc80aa9c114e041
Change History (13)
comment:1 Changed 10 years ago by
- Milestone changed from sage-3.4 to sage-3.4.1
comment:2 Changed 10 years ago by
- Cc jason added
comment:3 Changed 10 years ago by
Incorporating the time it takes to call fast_float, the speedup is not that radical:
sage: var('x') x sage: from sage.ext.fast_eval import fast_float sage: timeit("find_root(sin(x)-cos(x), 0, pi)") 625 loops, best of 3: 441 µs per loop sage: timeit("find_root(fast_float(sin(x)-cos(x), x), 0, pi)") 625 loops, best of 3: 393 µs per loop
Its better for clients to call fast_float themselves, if they're using find_root inside a loop.
comment:4 Changed 9 years ago by
- Report Upstream set to N/A
There is a small speedup here, so why not call it?
comment:5 Changed 9 years ago by
The point is that there should be a big speedup--I'm going to try and track down why construction is so expensive.
comment:6 Changed 6 years ago by
- Milestone changed from sage-5.11 to sage-5.12
comment:7 Changed 5 years ago by
- Milestone changed from sage-6.1 to sage-6.2
comment:8 Changed 5 years ago by
- Milestone changed from sage-6.2 to sage-6.3
comment:9 Changed 5 years ago by
- Milestone changed from sage-6.3 to sage-6.4
comment:10 Changed 2 years ago by
- Milestone changed from sage-6.4 to sage-duplicate/invalid/wontfix
- Status changed from new to needs_review
Actually the speedup is 13x here (Sage 7.5beta5) only if the fast float already exists.
sage: timeit("find_root(f, 0, pi)") 625 loops, best of 3: 131 µs per loop sage: timeit("find_root(g, 0, pi)") 625 loops, best of 3: 10.2 µs per loop sage: timeit("find_root(sin(x)-cos(x), 0, pi)") 625 loops, best of 3: 170 µs per loop sage: timeit("find_root(fast_float(sin(x)-cos(x), x), 0, pi)") 625 loops, best of 3: 161 µs per loop sage: timeit('_ = sin(x)-cos(x)') 625 loops, best of 3: 9.3 µs per loop sage: timeit("_ = fast_float(sin(x)-cos(x), x)") 625 loops, best of 3: 140 µs per loop
The creation of sin(x)-cos(x)
takes 10µs, find_root
of a fast float takes also 10µs. What is slow is creation of the fast float (130µs) and find_root
of the normal expression (120µs). So there is no gain converting to fast float because conversion eats it all.
Therefore I propose to close this ticket.
comment:11 Changed 20 months ago by
Sounds reasonable to me. Nice hunting.
comment:12 Changed 15 months ago by
- Status changed from needs_review to positive_review
comment:13 Changed 15 months ago by
- Resolution set to wontfix
- Status changed from positive_review to closed
3.4 is for ReST tickets only.
Cheers,
Michael