#12322: invalid simplification of complex logarithm
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Reporter: mjo | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: symbolics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by mjo):
Replying to [comment:2 kcrisman]:
The simplification should always be equivalent to the original expression,
though, or it isn't a simplification, it's a truncation (or something
else). It doesn't make much sense to have a `simplify()` that doesn't
return something equivalent to its argument: if I don't have to give you
the right answer, I can simplify anything to zero!
I did check simplify_log() back when this was reported, and that wasn't
the culprit. I dug a little deeper and found that it's `simplify_exp()` or
`simplify_radical()` that does it. They both use the same maxima function.
From the docs:
{{{
ALGORITHM:
This uses the Maxima "radcan()" command. From the Maxima
documentation: "All functionally equivalent forms are mapped into a
unique form. For a somewhat larger class of expressions, produces a
regular form. Two equivalent expressions in this class do not
necessarily have the same appearance, but their difference can be
simplified by radcan to zero. For some expressions radcan is quite
time consuming. This is the cost of exploring certain relationships
among the components of the expression for simplifications based on
factoring and partial fraction expansions of exponents."
}}}
That, at least, doesn't make any mention of invalid simplifications.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12322#comment:3>
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