Re: For loop problem in mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg90188] Re: [mg90163] For loop problem in mathematica*From*: Sseziwa Mukasa <mukasa at jeol.com>*Date*: Wed, 2 Jul 2008 05:27:16 -0400 (EDT)*References*: <200807011059.GAA14895@smc.vnet.net>

On Jul 1, 2008, at 6:59 AM, PhysNova wrote: > Hi, > i wrote a simple program of evaluating Pi number in M6 to test cpu > computation timing, to do this a simple for loop > > was used: > > x=0;For[i = 1, i < 10,000,000, i++, x = x + 1/(i^2)];N[Sqrt(6*x),25]// > Timing > > the result was catastrophe! it take few minuates. but i first expect > to do this very simple job in few > > seconds.computation time is just satisfactory up to 100000 cycle. > > could anyone interperet this falut? You are using exact arithmetic, Mathematica will constantly try to preserve precision, and simplify the expression x + 1/i^2 which adds computational complexity. > our get an idea to improve the result? If you don't care about exact results, use approximate numbers: x=N[0,25];For[i = 1, i < 10,000,000, i++, x =N[ x + 1/(i^2),25]];N [Sqrt(6*x),25]// Timing Regards, Ssezi

**References**:**For loop problem in mathematica***From:*PhysNova <skhoshbinfar@gmail.com>