Re: Request for Collective Wisdom...

*To*: mathgroup at smc.vnet.net*Subject*: [mg88703] Re: Request for Collective Wisdom...*From*: David Bailey <dave at Remove_Thisdbailey.co.uk>*Date*: Tue, 13 May 2008 07:09:46 -0400 (EDT)*References*: <fvpcoc$met$1@smc.vnet.net>

Here is a second tip. If a calculation is going very slowly, don't jump to the conclusion that you need to use a more functional programming style - at least without a little investigation. A spectacular way to consume machine time is to create an algorithm - say an iterative approximation to a square root - that is meant for real data, and then give it an argument such as Sqrt[3]/2. If the algorithm does not use explicit real numbers, and does not use N for example, it will build up a huge expression involving roots and fractions. This is particularly subtle if you simply give the output to Plot - which will apply N - your calculation will run extremely slowly and yet appear to work (if it ever terminates). David Bailey http://www.dbaileyconsultancy.co.uk