Status: Accepted
Owner: ronan.l...@gmail.com
Labels: Type-Defect Priority-Medium WrongResult EasyToFix
New issue 2241 by ronan.l...@gmail.com: Wrong convergence check for evalf()
of hypergeometric sums
http://code.google.com/p/sympy/issues/detail?id=2241
In sympy/core/evalf.py, check_convergence() assumes wrongly that the
denominator is monic, which causes a bug in master when that's not the
case. For instance, Sum((2*n+3)/(3*n**2+4), (n,0, oo)).evalf() returns
5.15367235167871 even though the series is obviously logarithmically
divergent.
A simple solution is to replace the last line of check_convergence() with:
return rate, constant, (qc-pc)/dpol.LC()
Tests should be added, for instance the example above.
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