Function Memoization

re: Function Memoization

pawan koshti — Sun, 09 Jan 2011 15:04:16 GMT

using System;

using System.Data;

using System.Configuration;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

/// <summary>

/// Summary description for fibonancy

/// </summary>

public class fibonancy

{

int[] arr=new int[100];

int k;

int cal1=0;

int[] arr1 = new int[100];

public fibonancy()

{

for (int i = 0; i < 100; i++)

arr[i] = -1;

}

public int CAL1

{

get { return cal1; }

}

public int[] pr1

{

set

{

for (int i = 0; i < 100; i++)

{

arr1[i] = arr[i];

}

public int pr2

{

set { k = value; }

}

public int fib(int n)

{

//int s = getnthnumber(n);

if (n < 3)

{

arr[n] = 1;

return 1;

}

else if (getnthnumber(n) > -1)

return getnthnumber(n);

else

{

cal1++;

int nval = 0;

nval = fib(n - 1) + fib(n - 2);

setnthnumber(n, nval);

return nval;

}

public int getnthnumber(int n)

{

if (arr[n] != -1)

{

k = arr[n];

return k;

}

else

return -1;

}

public void setnthnumber(int n, int val)

{

arr[n] = val;

}

public int[] returnarr()

{

return arr;

}

re: Function Memoization

pawan — Sun, 09 Jan 2011 15:02:16 GMT

using System;

using System.Data;

using System.Configuration;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

/// <summary>

/// Summary description for fibonancy

/// </summary>

public class fibonancy

{

int[] arr=new int[100];

int k;

int cal1=0;

int[] arr1 = new int[100];

public fibonancy()

{

for (int i = 0; i < 100; i++)

arr[i] = -1;

}

public int CAL1

{

get { return cal1; }

}

public int[] pr1

{

set

{

for (int i = 0; i < 100; i++)

{

arr1[i] = arr[i];

}

public int pr2

{

set { k = value; }

}

public int fib(int n)

{

//int s = getnthnumber(n);

if (n < 3)

{

arr[n] = 1;

return 1;

}

else if (getnthnumber(n) > -1)

return getnthnumber(n);

else

{

cal1++;

int nval = 0;

nval = fib(n - 1) + fib(n - 2);

setnthnumber(n, nval);

return nval;

}

public int getnthnumber(int n)

{

if (arr[n] != -1)

{

k = arr[n];

return k;

}

else

return -1;

}

public void setnthnumber(int n, int val)

{

arr[n] = val;

}

public int[] returnarr()

{

return arr;

}

re: Function Memoization

VIsh — Mon, 12 Jul 2010 15:42:40 GMT

Hi Wes,

Do you think that this is a good way to cache results from REST webservices that are safe to cache when using Silverlight or the .NET framework?

If I could do that, then caching the results in the ASP.NET cache would be a good thing to do.

Thank You,

Vish

re: Function Memoization

Romain Verdier — Sat, 03 May 2008 02:04:56 GMT

Pingback from :

http://codingly.com/2008/05/02/optimisation-des-invocations-dynamiques-de-methodes-en-c/

re: Function Memoization

Kiryl Batsiukov — Wed, 14 Feb 2007 01:13:36 GMT

Great!

I finaly understood why was Lambda Calculus included in my Informatics Lectures at the university:)

Thanx for your post

Baby Names, Nameless Keys, and Mumbling

Yet Another Language Geek — Sun, 11 Feb 2007 09:49:39 GMT

Baby Names I recently finished reading Freakonomics . It is a fascinating book about a number of strange

re: Function Memoization

wesdyer — Fri, 02 Feb 2007 20:41:39 GMT

James:

Probably the easiest way to make Memoize thread-safe is to put a lock on map. Like so:

public static Func<A, R> Memoize<A, R>(this Func<A, R> f)

{

var map = new Dictionary<A, R>();

return a =>

{

lock (map)

{

R value;

if (map.TryGetValue(a, out value))

return value;

value = f(a);

map.Add(a, value);

return value;

}

};

}

This will ensure that the function that is being memoized will only be run once for each set of distinct arguments.

In my example of the RoboRally game, I actually used function memoization to act as "surrogate singleton". It isn't really a singleton since there can be one instance per factory instance (unless the factory is static). But that is exactly what I wanted.

Community Convergence XX

Charlie Calvert's Community Blog — Fri, 02 Feb 2007 11:10:36 GMT

Welcome to the twentieth Community Convergence. I'm Charlie Calvert, the C# Community PM, and this is

Community Convergence XX

Charlie Calvert's Community Blog — Fri, 02 Feb 2007 10:52:40 GMT

Welcome to the twentieth Community Convergence. I'm Charlie Calvert, the C# Community PM, and this is

re: Function Memoization

James Jones — Thu, 01 Feb 2007 17:09:35 GMT

Hi Wes

Thank you for the feedback .. it's appreciated.

I'm very much an OOP minded programmer who is trying very hard to appreciate and adopt a more functional style of programming that will inherently promote thread neutral development. The idea being that my applications scale naturally on multi-processor machines into the future.

I'm currently working on a system, part of which involves delegating well known interface type instantiation to a factory class. What I'd really like is a way of promoting Singleton type usage of types that do not necessarily implement that pattern themselves. It struck me that your memorize function could be just the ticket to this ... kindof a surrogate singleton.

Thank you for taking the time to respond and please keep up the excellent posts.

James