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Re: For loop problem in mathematica
*To*: mathgroup at smc.vnet.net
*Subject*: [mg90258] Re: For loop problem in mathematica
*From*: "Dana DeLouis" <dana.del at gmail.com>
*Date*: Thu, 3 Jul 2008 06:14:17 -0400 (EDT)
> For[i = 1, i < 10,000,000, i++, x = x + 1/(i^2)];
Just to add. The "HarmonicNumber" of 10,000,000 is very large to be done
quickly.
If you wish Machine Precision, perhaps another idea:
Timing[Sqrt[6*HarmonicNumber[10000000., 2]]]
{0.`, 3.1415925580968302`}
Just a note:
The Numerator of just 100,000 has about 87,000 digits in it.
HarmonicNumber[100000, 2] // Numerator // IntegerLength
86904
--
HTH :>)
Dana DeLouis
Mathematica 6.01 (Windows Vista)
Having to Read 5.0 Help Files
"PhysNova" <skhoshbinfar at gmail.com> wrote in message
news:g4d2qf$emo$1 at smc.vnet.net...
> 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?
> our get an idea to improve the result?
>
> Tanks
>
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