maxima: maxima hangs (infinite loop?)



forwarded 198466 maxima@math.utexas.edu
tags 198466 +upstream
tags 198466 +confirmed
thanks

A Debian user submitted this report, which I'm also registering at the
website.  Any ideas on a fix?

Take care,

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When trying to do some complicated Taylor series expansions, maxima
hangs; I believe it is in an infinite loop, as xload shows the cpu
saturated.

An example is:

	f(x):= asin(sqrt(1-x^2)/(1+eps));

	taylor(f(x),x,0,2);

which produces this condition.  While trying to isolate the bug, I tried:

	g(x):=asin(sqrt(1-x^2));

	taylor(g(x),x,0,2);

which produces the error message:

	"Taylor encountered an unfamiliar singularity in ABS(X)"

I am unable to find any documentation on this "unfamiliar singularity"
error message.  However, from looking at the second derivative of G(x),
I think I can see what's causing the problem: the sqrt() in the above
expression is symmetrical about x=0, but has a cusp there.  However, this
ought to cause taylor() to produce an error message in the first example,
instead of looping; this is not very user-friendly.

What's the difference between a familiar singularity and an unfamiliar
one, anyway?
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-- 
Camm Maguire			     			camm@enhanced.com
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"The earth is but one country, and mankind its citizens."  --  Baha'u'llah