Re: Re: $RecursionLimit Bug?
- To: mathgroup at smc.vnet.net
- Subject: [mg63960] Re: [mg63939] Re: [mg63932] $RecursionLimit Bug?
- From: <bsyehuda at gmail.com>
- Date: Wed, 25 Jan 2006 08:45:45 -0500 (EST)
- References: <200601230911.EAA04880@smc.vnet.net> <200601240630.BAA23611@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi Pratik,
This will consum too much memory.
One can make a compromise if the systems stack limit is known (can be
revealed with some experimentation). Store intermediate results only in
known points that will prevent the stack overflow
The following can serve as an example
f[0]=1;
f[x_]:=If[Mod[x,10000]==0,f[x]=x f[x-1],x f[x-1]]
$RecursionLimit=Infinity
so
Table[f[x],{x,10000,100000,10000}]
will store the results in the points determined by the Table iterator and
the definition of the function
This way of a forward calculation let youget results for f[10*^5 and above].
The payment is ofcourse with computation time (the condition is checked in
each steps) but this gives results in a very resonable time.
regards
yehuda
On 1/24/06, Pratik Desai <pdesai1 at umbc.edu> wrote:
>
> W. Craig Carter wrote:
>
> >Hello,
> >I am using Mathematica 5.2 on MacOS 10.4.4
> >
> >I was trying to construct a cannonical timing example by writing
> >a memoryless factorial function.
> >
> >If I do this (fresh kernel):
> >
> >$RecursionLimit = $IterationLimit = 10^6
> >fact[0] = 1;
> >fact[n_] := n fact[n - 1]
> >Timing[fact[10^6]]
> >?fact
> >This generates no output, and the ?fact input line becomes In[1], as
> >if the kernel died after Timing[fact[10^5]], but no messages are
> >generated.
> >
> >If I bury the recursion limit inside a Block, then I get
> >fact[0] = 1;
> >fact[n_] := n fact[n - 1]
> >Timing[Block[{$RecursionLimit = Infinity}, Return[fact[10^5]]]]
> >-----> $RecursionLimit::reclim : Recursion depth of 256 exceeded
> >?fact (* now is In[1] *)
> >-----? Symbol fact not found.
> >
> >
> >Is this a bug? I couldn't find a list of known bugs on the
> >mathematica site....
> >
> >
> >Thanks, WCC
> >
> >
> >
> >W. Craig Carter
> >Lord Foundation Professor of Materials Science and Engineering
> >MIT, Dept. of Materials Science and Engineering 13-5018 77 Massachusetts
> Ave, Cambridge, MA 02139-4307 USA
> >617-253-6048 ccarter at mit.edu http://pruffle.mit.edu/~ccarter
> http://pruffle.mit.edu/~ccarter/FAQS/
> http://pruffle.mit.edu/~ccarter/I_do_not_use_microsoft.html
> >
> >
> >
> There is an example similar to this in the Mathematic Book in section
> 2.5.9
> 2.5.9 Functions That Remember Values They Have Found
> Here is one that I modified a bit with RecursionLimit set to infinity
>
> In[27]:=
> Clear[f,x]
> $RecursionLimit=Infinity
> f[x_]:= f[x]=x*f[x- 1]
> f[0]=f[1]=1
> Timing[f[10^4]]//Short
>
> Out[28]=
> ∞
>
> Out[30]=
> 1
>
> Out[31]//Short=
> {0.23 Second,2846259\[LeftSkeleton]35645\[RightSkeleton]00000000}
>
> Hope this helps
>
> Pratik
>
>
- References:
- $RecursionLimit Bug?
- From: "W. Craig Carter" <ccarter@mit.edu>
- Re: $RecursionLimit Bug?
- From: Pratik Desai <pdesai1@umbc.edu>
- $RecursionLimit Bug?