#3037 Integrate should not be null

[Samuel]

integrate(x*sin(x)*exp(-1/2x^2),x,minf,inf);

is zero whereas by ipp we get

integrate(cos(x)*exp(-1/2x^2),x,minf,inf);

which is
[\frac{\sqrt{2}\,\sqrt{\pi }}{\sqrt{e}}]

wxMaxima version: 13.4.0
Maxima version: 5.32.1
Maxima build date: 2014-01-10 01:52:55
Host type: x86_64-unknown-linux-gnu
Lisp implementation type: GNU Common Lisp (GCL)
Lisp implementation version: GCL 2.6.10

[Samuel]

Sorry : ipp stands for integration by parts.

[Raymond Toy]

Update your version of maxima. Current git maxima says

(%i1) integrate(x*sin(x)*exp(-1/2*x^2),x,minf,inf);
(%o1) (sqrt(2)*sqrt(%pi))/sqrt(%e)

[sslavi]

But the current SBCL Maxima says "zero" again...

[Raymond Toy]

Don't know what's up with that. Perhaps an issue with sbcl on windows?

I just checked out maxima 5.37.2 and the test on my linux box with cmucl, gcl, and sbcl. They all return the correct answer.

[sslavi]

Very possibly so.
Is it possible for you guys to release the GCL version of Maxima 5.37.2 for Windows too?
SBCL seem to be related to a number of bug reports and CLISP is way too slow for complex probles.

[Andrej Vodopivec]

Do you have any packages loaded. I can't reproduce this on Windows:

(%i1) wxbuild_info()$
wxMaxima version: 15.8.2
Maxima version: 5.37.2
Maxima build date: 2015-09-18 21:03:17
Host type: i686-pc-mingw32
System type: Win32 6.2.9200 X86
Lisp implementation type: SBCL
Lisp implementation version: 1.2.7
(%i2) integrate(x*sin(x)*exp(-1/2*x^2),x,minf,inf);
(%o2) (sqrt(2)*sqrt(%pi))/sqrt(%e)

[sslavi]

Very interesting!!
Yes, I have my personalized .mac file loaded by default, and I've found the culprit: the radexpand flag!

If the radexpand is set to "true", the correct solution (sqrt(2)sqrt(%pi))/sqrt(%e) is returned.

If the radexpand is set to "all", the wrong solution 0 is returned.

Samuel, it would be interesting to see what is the default value of the radexpand flag in your Maxima session.

[Samuel]

My default value of radexpand flag is true. But with radexpand is set to "false", I get the correct answer!
Thanks a lot.

[Samuel]

Where can I find an updated version of maxima for a 64 bit architecture?

[sslavi]

As far as I know, this is where all Maxima releases are stored, so the most update version is this one: https://sourceforge.net/projects/maxima/files/Maxima-Windows/5.37.2-Windows/

[Samuel]

Thank you, but my question was unprecise. I work on Linux and all the versions in the Maxima-Linux folder are labeled i386 so basically 32 bit. Even my current version 5.32.1 !!!
But I get my answer for the main question and I know now that it is not a question of updating.

[sslavi]

One question still remains.
Why do I get the correct result with "radexpand" set to "true", and you don't?

[Samuel]

Maybe there are some flags involved but I am not familiar with it. At least, do you get the correct answer when "radexpand" set to "false"?

[sslavi]

Yes I do.

[David Scherfgen]

This has been fixed by now, unclear in which commit.