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last edited 6 years ago by test1 |
Edit detail for #294 Infinite recursion during integration revision 7 of 8
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Editor: alfredo
Time: 2008/10/16 12:56:27 GMT-7 |
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From alfredo Thu Oct 16 12:56:27 -0700 2008
From: alfredo
Date: Thu, 16 Oct 2008 12:56:27 -0700
Subject:
Message-ID: <20081016125627-0700@axiom-wiki.newsynthesis.org>
Status: fixed somewhere => fix proposed
The following input causes infinite recursion in rischNormalize
axiom
integrate(simplify(D((log((x)+1)+a)/(2*((((x*(exp(exp(x)/2)))-(a*(x+exp(-x/2))))*(2/x))-3)),x)), x)
![\label{eq1}{{x \ {\log \left({x + 1}\right)}}+{a \ x}}\over{\left(
\begin{array}{@{}l}
\displaystyle
{4 \ x \ {{e^{\left(-{x \over 2}\right)}}^2}\ {e^{{{2 \ x \ {{e^{\left(-{x \over 2}\right)}}^2}}+ 1}\over{2 \ {{e^{\left(-{x \over 2}\right)}}^2}}}}}-{4 \ a \ {e^{\left(-{x \over 2}\right)}}}+
\
\
\displaystyle
{{\left(-{4 \ a}- 6 \right)}\ x}](images/2198410976292048843-16.0px.png "\label{eq1}{{x \ {\log \left({x + 1}\right)}}+{a \ x}}\over{\left(
\begin{array}{@{}l}
\displaystyle
{4 \ x \ {{e^{\left(-{x \over 2}\right)}}^2}\ {e^{{{2 \ x \ {{e^{\left(-{x \over 2}\right)}}^2}}+ 1}\over{2 \ {{e^{\left(-{x \over 2}\right)}}^2}}}}}-{4 \ a \ {e^{\left(-{x \over 2}\right)}}}+
\
\
\displaystyle
{{\left(-{4 \ a}- 6 \right)}\ x}") | (1) |
Type: Union(Expression(Integer),
AFAICS goodCoef chooses to rewrite simpler kernel in terms of a more complex one. More precisely, rischNormalize is supposed to eliminate kernels which are algebraically dependent on other kernels. If a dependent kernel is found rischNormalize should eliminate it and recurse. So the recursion depth is limited by the number of kernels. However, in this example rischNormalize eliminates simpler kernel, but causes new kernels to appear.
elementary integration really should be one of the strengths... --kratt6, Sat, 03 Jun 2006 07:52:55 -0500 reply
Category: Aldor Library Compiler => Axiom Library
Severity: normal => serious
Status: open => fix proposed
Status: fix proposed => fixed somewhere
no patch available
http://axiom.svn.sourceforge.net/viewvc/axiom/branches/wh-sandbox/src/algebra/efstruc.spad.pamphlet?r1=263&r2=377 Status: fixed somewhere => fix proposed