memoization

Possible Duplicate: When is memoization automatic in GHC Haskell? As a consequence, pure function always returns the same value for a fixed input. That said, does Haskell (more precisely GHC) automatically cache (memoize) these results if there is enough memory (question 1) and does developer have any control on it (question 2)? Philip JF I voted to close, but short answer: GHC does not do any automatic memoization of functions, and that is probably a good thing because it would make space complexity even harder to reason about. Also, memoization is not in general a very solvable problem,

Is there a way to memoize the output of a function to disk? I have a function def getHtmlOfUrl(url): ... # expensive computation and would like to do something like: def getHtmlMemoized(url) = memoizeToFile(getHtmlOfUrl, "file.dat") and then call getHtmlMemoized(url), so as to do the expensive computation only once for each url. georg Python offers a very elegant way to do this - decorators. Basically, a decorator is a function that wraps another function to provide additional functionality without changing the function source code. Your decorator can be written like this: import json def

I'm working on some fairly computational intensive calculations that deal with numpy matrices and ndarrays, and from some digging around, there are about a dozen ways not to implement memoization, generally full of collisions, and issues with ndarrays being mutable objects. Has anyone come across a fairly general memoisation decorator that can handle numpy objects? How about this package: http://packages.python.org/joblib/memory.html An alternative is my package jug: http://packages.python.org/Jug It is similar to joblib, but with a slightly different approach. 来源： https://stackoverflow.com

I'm trying to write a function that returns a memoized recursive function in Clojure, but I'm having trouble making the recursive function see its own memoized bindings. Is this because there is no var created? Also, why can't I use memoize on the local binding created with let? This slightly unusual Fibonacci sequence maker that starts at a particular number is an example of what I wish I could do: (defn make-fibo [y] (memoize (fn fib [x] (if (< x 2) y (+ (fib (- x 1)) (fib (- x 2))))))) (let [f (make-fibo 1)] (f 35)) ;; SLOW, not actually memoized Using with-local-vars seems like the right

I was trying to understand how memoization works in C++, so I looked at an example of memoization used in Fib. sequence. std::map<int, int> fibHash; int memoized_fib (int n) { std::map<int, int>::iterator fibIter = fibHash.find(n); if( fibIter != fibHash.end() ) return *fibIter; int fib_val; if( n <=1 ) fib_val = 1; else fib_val = memoized_fib ( n-1 ) + memoized_fib ( n-2 ); fibHash[ n ] = fib_val; return fib_val; } I was a little confused with how the fibHash[n] works. Does it just hold the individual values of each fib(#)? Also, the iterator traversess through the index to look for the

Let's say I have this code ( fiddle ) intended to memoize modules: var chat = { // Create this closure to contain the cached modules module: function() { // Internal module cache. var modules = {}; console.log('in module:', name); // <---------- "in return: result" // Create a new module reference scaffold or load an // existing module. return function(name) { console.log('in return:', name); // <---------- "in return: derp" // If this module has already been created, return it. if (modules[name]) { return modules[name]; } // Create a module and save it under this name return modules[name] = {

I am stumped with this memoize problem. I need to create a function that will check to see if a value has already been calculated for a given argument, return the previous result, or run the calculation and return that value. I have spent hours on this and while I am new to JS. I cannot get my head around how to do this. I cannot use any built in functions and would really like to understand what I need to do. Here is what I have so far, which is so wrong it feels like pseudo-code at this point. I have searched existing memoize questions out here but I cannot seem to make any solution work yet

I came across an interesting problem and was wondering if and how could this be done in Java: Create a method which can memoize any function/method . The method has the following arguments : the method/function and the argument(s) for it. For example let's say i have this method : int addOne(int a) { return a + 1;} and i call my memoization method two times with the same arguments : addOne and 5 for example, the first call should actually call the addOne method and return the result and also store that result for that given argument. The second time when i call it should know this has been

Obviously ||= won't work def x? @x_query ||= expensive_way_to_calculate_x end because if it turns out to be false or nil , then expensive_way_to_calculate_x will get run over and over. Currently the best way I know is to put the value into an Array : def x? return @x_query.first if @x_query.is_a?(Array) @x_query = [expensive_way_to_calculate_x] @x_query.first end Is there a more conventional or efficient way of doing this? UPDATE I realized that I wanted to memoize nil in addition to false - this goes all the way back to https://rails.lighthouseapp.com/projects/8994/tickets/1830