#2607: find_minimum_on_interval() uses the wrong scipy function
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Reporter: AlexGhitza | Owner: jwmerrill
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: calculus | Resolution:
Keywords: sd31 | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by ddrake):
I just ran into this bug with the following input:
{{{
find_maximum_on_interval(fast_float(8*e^(-x)*sin(x) - 1, x), 0, 8)
(1.5791755355586754, 0.78539817769603915)
find_maximum_on_interval(fast_float(8*e^(-x)*sin(x) - 1, x), 0, 9)
(-0.9951835373923219, 7.0685835435476418)
}}}
...and was truly surprised that `find_maximum_on_interval` is not
monotonic (in the sense that a bigger interval should always give a
(weakly) bigger maximum)!
At the VERY LEAST, we should fix the documentation to specify that this
finds ''local'' extrema, and perhaps change the name of the function, too,
since it does ''not'' always find the actual maximum value on the
interval!
Note that one strange workaround is to simply plot the function; something
like:
{{{
def find_maximum_on_interval(f, a, b):
return plot(f, a, b).ymax()
}}}
seems like it would be pretty effective, despite being inelegant and
crude!
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/2607#comment:15>
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