Re: Looping

*To*: mathgroup at smc.vnet.net*Subject*: [mg95991] Re: Looping*From*: David Bailey <dave at removedbailey.co.uk>*Date*: Sat, 31 Jan 2009 06:44:01 -0500 (EST)*References*: <glmt16$mqu$1@smc.vnet.net> <200901291056.FAA18117@smc.vnet.net> <glvk9h$e4d$1@smc.vnet.net>

Andrzej Kozlowski wrote: > > > I doubt very much that they they ever get "stuck" in the way you > describe. Both Simplify and FullSimplify make use of algebraic > algorithms some of which have very high complexity (e.g. exponential > or even double exponential in the number of variables). > > > Andrzej Kozlowski > I was responding to a user who tells us he has left a calculation running for 3 days! He hadn't used TimeConstraint when he started the thing off, so it could not help him until he killed the process. I have certainly had Simplify and FullSimplify get 'stuck' - though I have never waited 3 days for a possible answer (and I am yet to encounter this problem with 7.0, but I have not tried)! In situations like this - which often spread over a lot of memory - the computer ends up swapping memory pages to/from disk, which slows the actual calculation to a crawl. I would have thought I replied with the obvious practical advice, and that the word 'stuck' is sufficiently vague and informal as not to require a paragraph of mathematical caveats! David

**References**:**Re: Looping***From:*David Bailey <dave@removedbailey.co.uk>