login  home  contents  what's new  discussion  bug reports     help  links  subscribe  changes  refresh  edit
IssueTracker
#293 integrate 1/(1+x^2)  ← ↑ →  #295 PERM movedPoints wrong

#294 Infinite recursion during integration
  
last edited 6 years ago by test1

Edit detail for #294 Infinite recursion during integration revision 8 of 8
1 2 3 4 5 6 7 8
Editor: test1
Time: 2018/02/08 16:25:29 GMT+0
Note: 
added:

From test1 Thu Feb 8 16:25:29 +0000 2018
From: test1
Date: Thu, 08 Feb 2018 16:25:29 +0000
Subject: 
Message-ID: <20180208162529+0000@axiom-wiki.newsynthesis.org>

Status: fix proposed => closed

Submitted by : (unknown) at: 2007-11-17T22:22:32-08:00 (17 years ago)
Name :
Axiom Version :
Category : Severity : Status :
Optional subject :  
Optional comment :

The following input causes infinite recursion in rischNormalize

fricas
(1) -> 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}\frac{{x \ {\log \left({x + 1}\right)}}+{a \ x}}{{4 \ x \ {{{e}^{-{\frac{x}{2}}}}^{2}}\ {{e}^{\frac{{2 \ x \ {{{e}^{-{\frac{x}{2}}}}^{2}}}+ 1}{2 \ {{{e}^{-{\frac{x}{2}}}}^{2}}}}}}-{4 \ a \ {{e}^{-{\frac{x}{2}}}}}+{{\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

Fixed in FriCAS --kratt6, Thu, 20 Dec 2007 01:17:58 -0800 reply
Status: open => fix proposed

... --gdr, Sun, 18 May 2008 13:40:08 -0700 reply
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

... --alfredo, Thu, 16 Oct 2008 12:56:27 -0700 reply
Status: fixed somewhere => fix proposed

... --test1, Thu, 08 Feb 2018 16:25:29 +0000 reply
Status: fix proposed => closed