Re: calculate Recurrence Equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg68791] Re: [mg68713] calculate Recurrence Equations*From*: gardyloo <gardyloo at mail.wsu.edu>*Date*: Fri, 18 Aug 2006 03:12:50 -0400 (EDT)*References*: <200608170818.EAA24918@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

The timing for that function fits very nicely to time[n]=10^(-5)*2^n with the prefactor of 10^-5 specific to my machine and the time in seconds. On my computer, at least, I'd estimate that anteil[30] would take almost exactly 3 hours. I had to look up how to define the functions so that Mathematica remembers the values of the functions as previously-calculated (otherwise it has to recalculate the things all over again each time it hits one). It takes only one little addition to your definition. Try this: anteil[0] = 1 anteil[n_] := anteil[n] = anteil[n - 1] + (anteil[n - 1]*5 - 1)/100 Now the thing should be virtually instantaneous (you could also define things to use numeric values rather than exact calculations by defining anteil[0] to be 1.0 or whatever, but I don't think it'll buy you much performance unless you're going up to n much larger than 30). Hope that helps! It helped me, by the way, by forcing me to look up how to define these things, which I'll need to do very shortly. C.O. Frank Hechtner wrote: > hi, > > i?m in trouble with my Recurrence Equations: > > i?ve defined the following function > > anteil[0] = 1 > anteil[n_] := anteil[n - 1] + (anteil[n - 1]*5 - 1)/100 > > i want mathematica to calculate the values for anteil[30] and so on. > > Unfortunately mathematica needs for this calculation over 2 hours (and > is still running, athlon x2 4600, 2 gb ram). > > I don?t see where are the difficulties for mathematica... > > Thanx for your help > > frank > > > -- ========================================================== Curtis Osterhoudt gardyloo at mail.remove_this.wsu.and_this.edu PGP Key ID: 0x088E6D7A Please avoid sending me Word or PowerPoint attachments See http://www.gnu.org/philosophy/no-word-attachments.html ==========================================================

**References**:**calculate Recurrence Equations***From:*Frank Hechtner <frank.hechtner@rub.de>