Re: Re: A bug of Integrate[] in Mathematica 4.1 (and 4.0)

*To*: mathgroup at smc.vnet.net*Subject*: [mg27443] Re: [mg27412] Re: A bug of Integrate[] in Mathematica 4.1 (and 4.0)*From*: George Woodrow <ardaghconsultants at worldnet.att.net>*Date*: Sun, 25 Feb 2001 20:55:47 -0500 (EST)*References*: <972f8t$4ea@smc.vnet.net> <974vgh$6h1@smc.vnet.net> <200102250553.AAA10789@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

The bug is still there is 4.1. the integral is i/2 what it should be. Curiously, if (r-x) (r+x) is re-written as (r^2 - x^2), Mathematica gets the right answer. NIntegrate works correctly. George Woodrow III >Jens-Peer Kuska wrote: > >> a) everyone that use a computer algebra and blind trust it's results >> is a born fool > >I might be a born fool but I'm never trusting CA systems in mathematical >results ;-). > >> b) don't call it "bug", call it feature > >Please call a bug a bug. I had a nice private discussion with someone >from Wolfram Res. who admitted now that it is a bug. I'm aware of the >fact that a fix of bugs of this kind is a rather complicated stuff. > >> c) WRI cares about this features > >Well, I was a little too naughty. I wanted also to say that I find >Mathematica a great tool, and it is impossible to get a multi purpose >CA-system without bugs. I was only complaining about some support team >emplyees who are telling me a bug is not a bug. > >> d) a modification in Integrate[] needs probably a full new kernel > >Fine. How about version 4.1? Could someone check the my simple example > >Integrate[sqrt[(r-x)(r+x)],{x,-r,r}] > > >> g) when a sufficient number of features are corrected we get a version >> x.y.1 typical for free -- just a e-mail to the sales department is >> needed, some days later a CD-ROM arrives you - can they do more ? > >Ok, is there such a CD-ROM for the student version of version 4.0? > >> h) I assume that a public list of known bugs would be bad publicity >> because the most people believe that a software must be complete >> bug free to work at all. Bad sales due to confused customers >> ("What ? Mathematica has bugs ???" =:-O ) can't be in the interest >> of any Mathematica user. > >No, I think that the users of Mathematica are smart enough to like such >bug reports. It is only helpful to avoid trouble from the very >beginning. At the long sight it is a bad politics for a software company >to hide errors. Wolfram research has some bug lists, as I have learned >from my correspondence. It is not of my interest to make Mathematica >worse saled than now. > >The behaviour you advertise for software companies might be the reason >that sometimes non-commercial software is more stable than commercial. >It is also very easy to communicate with open source software developers >because they have no interest in hiding bugs but in finding bugs and >cure them, and the best thing for a CA-system is to have bug reports >from real users of the system, applying it in their practical work. >Since Mathematica is so general there are a lot of different communities >using it for a lot of different task so that it is easy to find many >different kinds of bugs which again is a chance to fix them for the next >version. > >But if I hear mathematically questionable arguments that a bug is not a >bug or, even worse, that a bug is a feature as you did above, I have not >much confidence that the bug will be fixed in a later version, because >arguing in this way prevents developing better algorithms. > > >-- >Hendrik van Hees Phone: ++49 6159 71-2751 >c/o GSI-Darmstadt SB3 3.183 Fax: ++49 6159 71-2990 >Planckstr. 1 mailto:h.vanhees at gsi.de >D-64291 Darmstadt http://theory.gsi.de/~vanhees/index.html

**References**:**Re: A bug of Integrate[] in Mathematica 4.1 (and 4.0)***From:*Hendrik van Hees <h.vanhees@gsi.de>