Richard in Reading on Fri, 26 Apr 2013 15:57:21 +0200

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Trying to factor a number a bit but not hanging the program for hours

As part of a pari program I'm trying to factor certain large numbers but then give up if a factorization isn't easily achievable. I've been using factorint(n,9) with the expectation that it will always complete reasonably quickly.



runs for hours whereas 

factorint( 450448646198249 * 7187991967803917, 9)
[3237821250781162225771540741333 1]

returns straight away even though I'm supplying a composite. 
Note that factor() returns the above factors in about 0.2 of a second.

It would be nice to have a decent factoring function which spends a certain amount of time trying to factor a number and then gives up. I seem to remember seeing a script on the web which could do it in pari using the default factoring function but using some function in combination with trap to interrupt its execution after a time.
Can anyone help?



PS Thanks to Dirk Laurie for solving my sqrt complaint!