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MathGroup Archive 1997

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Integration bugs in Mathematica 3.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg9213] Integration bugs in Mathematica 3.0
  • From: carlos at mars.Colorado.EDU (Carlos A. Felippa)
  • Date: Fri, 24 Oct 1997 01:00:28 -0400
  • Organization: University of Colorado, Boulder
  • Sender: owner-wri-mathgroup at wolfram.com

In a recent FEM project assigned as HW, about one third of the Integrate
results (216 out of roughly 600)  were wrong.   Extracted sample:

fu=(2+Cos[phiQ])/Sqrt[6-2*Cos[phiQ]*(-2+Cos[theta])-4*Cos[theta]];
BQ=Integrate[fu,{theta,0,Pi}]; 
Print["BQ=",BQ//InputForm];
fu=fu/.{phiQ->0};
BQ=Integrate[fu,{theta,0,Pi}]; 
Print["BQ=",BQ//InputForm];

Results:

BQ=0   (* wrong *)
BQ=3*EllipticK[-3]  (* demonstrates bug *)

The students were not amused.  2.2 does it right, but most of them did
not have access to it on campus machines.

Further, Integrate takes 2-5 times longer than in 2.2.


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