       Re: Mathematica slows down

• To: mathgroup at smc.vnet.net
• Subject: [mg52964] Re: [mg52956] Mathematica slows down
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sat, 18 Dec 2004 03:59:37 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```I don't know what changes; however, you can speed it up by avoiding
repeated calls of Prime for the same values

NumP=15000;

Table[pk[n]=Prime[n],{n,NumP}];

For[k=1,k<NumP,k++,
Gap=pk[k+1]-pk[k];
Gap=pk[k+2]-2pk[k+1]+pk[k];
Gap=pk[k+3]-3pk[k+2]+3pk[k+1]-pk[k];
Gap=pk[k+4]-4pk[k+3]+6pk[k+2]-4pk[k+1]+pk[k];
If[Mod[k,1000]==0,Print[k]]]

Bob Hanlon

>
> From: George Szpiro <george at netvision.net.il>
To: mathgroup at smc.vnet.net
> Date: 2004/12/17 Fri AM 05:20:43 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg52964] [mg52956] Mathematica slows down
>
> Hello,
>
> the following program runs ok for the first 6,000 iterations, then slows
> down considerably, and then seems to speed up again after 10,000. Does
> anyone know what is going on?
>
> Thanks,
> George
>
>
> NumP=15000;
>
> For[k=1,k<NumP,k++,
>
>   Gap=Prime[k+1]-Prime[k];
>   Gap=Prime[k+2]-2Prime[k+1]+Prime[k];
>   Gap=Prime[k+3]-3Prime[k+2]+3Prime[k+1]-Prime[k];
>   Gap=Prime[k+4]-4Prime[k+3]+6Prime[k+2]-4Prime[k+1]+Prime[k];
>
>   If[Mod[k,1000]==0, Print[ k]]
>
>
>   ]
>
>
>

```

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