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Submitted by : (unknown) at: 2007-11-17T22:22:32-08:00 (10 years ago)
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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}
(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

From wh-sandbox --alfredo, Thu, 28 Aug 2008 18:46:46 -0700 reply
http://axiom.svn.sourceforge.net/viewvc/axiom/branches/wh-sandbox/src/algebra/efstruc.spad.pamphlet?r1=263&r2=377

Status: fixed somewhere => fix proposed




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