Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Re: NestListEffects function not working in 6.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77170] Re: [mg77059] Re: NestListEffects function not working in 6.0
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Tue, 5 Jun 2007 06:39:58 -0400 (EDT)
  • References: <f3ofsh$p6j$1@smc.vnet.net> <19984802.1180984441947.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

I suspect you're calling the function improperly... but I can't test that  
theory without know how you're calling it. I've written a replacement,  
anyway, that I think does what you want - a lot more efficiently.

Clear[nestListEffects, sideFX, nestFX]
Options[nestListEffects] = {returnValues -> {#1 &, 1},
    sideEffects -> {}};
nestListEffects::usage =
   "nestListEffects[f, expr, n, returnValues -> {g, k}] returns a list \
of every kth element of NestList[f, expr, n] after the application of \
g. nestListEffects[f, expr, n, sideEffects -> {{g1, k1}, {g2, \
k2},...}] applies gi after every ki steps, but does not
   affect return values.";
sideFX[expr_, i_Integer][{gg_, kk_Integer}] :=
  Divisible[i, kk] && gg[expr, i]
nestFX[f_, g_, k_Integer, sides_List][{expr_, i_Integer}] :=
  Module[{e = f@expr},
   Divisible[i, k] && Sow@g[e, i];
   Scan[sideFX[e, i], sides];
   {e, i + 1}
   ]
nestListEffects[f_, expr_, n_Integer, opts___Rule] :=
   Module[{sides, ret, g,
     k}, {ret, sides} = {returnValues, sideEffects} /. {opts} /.
      Options[nestListEffects]; {g, k} = ret;
    Reap[Nest[nestFX[f, g, k, sides], {expr, 1}, n]][[-1, 1]]
    ];

Here's a test:

nestListEffects[2 # &, 1, 100, returnValues -> {{##} &, 20},
  sideEffects -> {{Print[{##}] &, 15}}]

{32768,15}

{1073741824,30}

{35184372088832,45}

{1152921504606846976,60}

{37778931862957161709568,75}

{1237940039285380274899124224,90}

{{1048576, 20}, {1099511627776, 40}, {1152921504606846976,
   60}, {1208925819614629174706176,
   80}, {1267650600228229401496703205376, 100}}

And here's a call that DOESN'T work properly:

nestListEffects[2 # &, 1, 100, returnValues -> {{##} &, 20},
  sideEffects -> {Print[{##}] &, 15}]

{{1048576, 20}, {1099511627776, 40}, {1152921504606846976,
   60}, {1208925819614629174706176,
   80}, {1267650600228229401496703205376, 100}}

I think that's precisely the kind of mistake you're making with your  
original function.

Bobby

On Sat, 02 Jun 2007 03:16:22 -0500, Jon Davis <jon_davis at mac.com> wrote:
> Sorry about the lack of specificity regarding problems in my last post.
> More details on my problem with NestListEffects follow.
>
> The NestListEffects function is basically an enhanced version of
> NestList. It does the same thing as NestList (applies a function f to
> an expression n times). It also does some other nifty stuff. For
> example, if I pass SideEffects -> {{printCounter, 10}} to
> NestListEffects as the opts___ argument, then the function prints out
> the number of iterations completed as NestList runs. For example, if n > is 200 and SideEffects ->{{printCounter, 10}}, then I'll get a count
> output every 10 iterations of NestList. That is,  in the notebook as
> NestList is processing, the numbers 0 10 20 ... 200 will print,
> sequentially, as the 200 steps are completed. This is very handy for
> complex functions and large data sets because it can take several hours
> for a simulation to complete and I can see how far things have
> progressed.
>
> NestListEffects worked in Mathematica 4.0 for sure. It doesn't seem to
> work in Mathematica 6.0. The simulations run correctly, so NestList is
> still properly applied. However, the numbers don't print out every 10
> iterations of the simulation...
>
> Hope this helps!
>
>
> On 2007-06-01 01:55:13 -0500, Jon Davis <jdavis at bus.wisc.edu> said:
>
>> I'm coming back to Mathematica after a couple of years and I just
>> upgraded to 6.0. I have relied on a function for quite awhile that I
>> got from a book by Richard Gaylord and Louis D'Andria titled
>> "Simulating Society".  The function is very useful for agent-based
>> simulations and for some reason, it doesn't seem to work in version
>> 6.0... No incompatibilities are identified by the version advisory
>> scanner, so I'm not sure what to do. Can anyone help? Functions follow.
>> Any help is deeply appreciated!!! I can provide a notebook with example
>> usage on request.
>>
>> NestListEffects::usage = "NestListEffects[f, expr, n, ReturnValues 
>> =E2=86=
>> =92
>> {g, k}] returns a list of every kth element of NestList[f, expr, n]
>> after the application of g. NestListEffects[f, expr, n, SideEffects  
>> =E2=86=
>> =92
>> {{g1, k1}, {g2, k2},...}] applies gi after every ki steps, but does not
>> effect return values.";
>>
>> ReturnValues::usage = "ReturnValues is an option to NestListEffects
>> that determines what is returned and how often.";
>>
>> SideEffects::usage = "SideEffects is an option to NestListEffects that
>> applies functions without effecting return values. The option
>> SideEffects does not affect return values";
>>
>> Options[NestListEffects]={ReturnValues-> {#&, 1}, SideEffects-> {}};
>>
>> NestListEffects[f_, expr_, n_, opts___]:= If[({ReturnValues,
>> SideEffects} /. {opts} /. Options[NestListEffects]) === {{#&, 1}, {
>> }},
>> NestList[f, expr, n],
>>    (* else *)
>>    Module[{c = 0, lis = {}, side, ret}, {ret, side} = {ReturnValues
>> ,
>> SideEffects} /. {opts} /. Options[NestListEffects];
>>     If[side === {}, side = {{Null, Infinity}}];
>>     Nest[( If[Mod[c, ret[[-1]]] === 0, lis = Join[lis, {First [ret
>> ][#, c]}]];
>>          Table[If[Mod[c, side[[i, -1]]] === 0, side[[i, 1]][#, c]],
>>  {i,
>> Length[side]}];
>>          c++;
>>          #)&[f[#]]&, expr, n];
>>     lis]
>>    ];
>
>
>



-- =

DrMajorBob at bigfoot.com


  • Prev by Date: Re: Graphics does not work: please comment.
  • Next by Date: Keyboard shortcut to select search bar in Mathematica 6 help window
  • Previous by thread: Re: NestListEffects function not working in 6.0
  • Next by thread: May 2007