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## #2506 factor(135*2^1204-1) infinity loop

None
closed
nobody
None
5
2012-12-07
2012-11-28
David Geistert
No

If you want to factor 135*2^1204-1 Maxima never end to calculate.

## Discussion

• Volker van Nek
2012-12-05

David, why do you think that Maxima never ends this calculation?
BTW: Do you know the prime factors? Which program did you use and how long does it take?

• David Geistert
2012-12-05

I don't know, if Maxima neverends. But after 3 hours calculation on an i7 I thougt it's supposed to be finished.
It would be very nice if you could implement a "max execution time" pararmeter or somthing like this.

• Volker van Nek
2012-12-05

The best free software for factoring integers I know is pari/gp. (In gp a quadratic sieve algorithm is implemented.) Perhaps you give it a try.

But be warned. You want to factor a 1200 bit integer. In case the two largest prime factors are of a size of about 600 bits you will have to wait for decades or for a completely new computer architecture.

I don't believe that a max execution time is a good idea. I think every user has to define his own time limit.

• David Geistert
2012-12-05

Thanks that you spend your time to help my in such a detailed way. I will try pari/gp then.

But is it possible to define a execution time limit? I searched in your documentation and in the man pages but I didn't find anything.

• Volker van Nek
2012-12-05

As far as I can tell the answer is no. There are some functions concerning time and date but there is no time limit function. Maxima does not perform multithreading and so it is not possible to run a second thread which controls the runtime of a computation.

If you don't want to kill a Maxima process manually it is possible to let another program do the job. E.g. run a shell script or a Java program which kills Maxima by calling a system command at a user defined time.

• David Geistert
2012-12-05

Oh, you are right, I totaly forgot that maxima isn't multithreading.
I think thats the best solution to run maxima in a python scripts or somthing else.
Finally I say thanks a lot to the whole maxima team and especially to you for the great job you did and support to do now.
Maybe maxima runs in some years with multithreading :)

• Volker van Nek
2012-12-07

• status: open --> closed
• milestone: --> None

• Volker van Nek
2012-12-07

There are no indications for a bug. So I close this ticket.