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• How to manipulate *huge* amounts of data

  - by Alejandro

  Hi there! I'm having the following problem. I need to store huge amounts of information (~32 GB) and be able to manipulate it as fast as possible. I'm wondering what's the best way to do it (combinations of programming language + OS + whatever you think its important). The structure of the information I'm using is a 4D array (NxNxNxN) of double-precission floats (8 bytes). Right now my solution is to slice the 4D array into 2D arrays and store them in separate files in the HDD of my computer. This is really slow and the manipulation of the data is unbearable, so this is no solution at all! I'm thinking on moving into a Supercomputing facility in my country and store all the information in the RAM, but I'm not sure how to implement an application to take advantage of it (I'm not a professional programmer, so any book/reference will help me a lot). An alternative solution I'm thinking on is to buy a dedicated server with lots of RAM, but I don't know for sure if that will solve the problem. So right now my ignorance doesn't let me choose the best way to proceed. What would you do if you were in this situation? I'm open to any idea. Thanks in advance!

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• On-Demand thumbnail creation with django and nginx

  - by sharjeel

  I want to generate thumbnails of images on the fly. My site is built with django and deployed using nginx which serves all the static content and communicates with django/apache using reverse proxy. Right now, for every image in my site, I generate all required sizes of thumbnails on-hand and deliver them when required. The problem is that whenever I change the size of a thumbnail, I have to regenerate all of them (and they are tons). However now I'd like to generate the thumbnail the first time it is accessed and later on nginx would deliver the same file over n over. If I delete that thumbnail file because of lesser accesses, it should get generated automatically the next time. Thumbnails in my case also have watermarks which require some computation logic of my application so a webserver thumbnail module might not work very well. The size of the thumbnail can be embedded in the URL. So http://www.example.com/thumbnail/abc_320x240.jpg gets the 320x240 size of the thumbnail. The approach I'm looking right now is to let nginx lookup the file and if it doesn't exist, forward the query to my django application which would create the thumbnail and send either the response or a redirect string. However I'm not sure about the concurrency issues and any other issues which might pop up later. What is the appropriate way to achieve this?

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• Linear regression confidence intervals in SQL

  - by Matt Howells

  I'm using some fairly straight-forward SQL code to calculate the coefficients of regression (intercept and slope) of some (x,y) data points, using least-squares. This gives me a nice best-fit line through the data. However we would like to be able to see the 95% and 5% confidence intervals for the line of best-fit (the curves below). What these mean is that the true line has 95% probability of being below the upper curve and 95% probability of being above the lower curve. How can I calculate these curves? I have already read wikipedia etc. and done some googling but I haven't found understandable mathematical equations to be able to calculate this. Edit: here is the essence of what I have right now. --sample data create table #lr (x real not null, y real not null) insert into #lr values (0,1) insert into #lr values (4,9) insert into #lr values (2,5) insert into #lr values (3,7) declare @slope real declare @intercept real --calculate slope and intercept select @slope = ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)), @intercept = avg(y) - ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)) * avg(x) from #lr Thank you in advance.

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• Moving from SVN to HG : branching and backup

  - by rorycl

  My company runs svn right now and we are very familiar with it. However, because we do a lot of concurrent development, merging can become very complicated.. We've been playing with hg and we really like the ability to make fast and effective clones on a per-feature basis. We've got two main issues we'd like to resolve before we move to hg: Branches for erstwhile svn users I'm familiar with the "4 ways to branch in Mercurial" as set out in Steve Losh's article. We think we should "materialise" the branches because I think the dev team will find this the most straightforward way of migrating from svn. Consequently I guess we should follow the "branching with clones" model which means that separate clones for branches are made on the server. While this means that every clone/branch needs to be made on the server and published separately, this isn't too much of an issue for us as we are used to checking out svn branches which come down as separate copies. I'm worried, however, that merging changes and following history may become difficult between branches in this model. Backup If programmers in our team make local clones of a branch, how do they backup the local clone? We're used to seeing svn commit messages like this on a feature branch "Interim commit: db function not yet working". I can't see a way of doing this easily in hg. Advice gratefully received. Rory

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• Stubbing an ActsAs Rails Plugin

  - by Rabbott

  I need to create a plugin much like Authlogic (or even just add on to Authlogic), but due to requirements beyond my control I need my plugin to authenticate using SOAP. Basically the plugin would require that anyone accessing the controller (before_filter would be fine) would have to authenticate first. I have ZERO control over the login page, or the SOAP server, I am simply a client attempting to authenticate to the providers SOAP Web Service. Here is what happens.. before_filter realizes that no session[:credential] is set, and forwards the user to the url on the providers servers. The user enters their credentials, and once authenticated, the web service forwards the user to a URL that has been entered by their sysadmins, attaching a token to the url on its way back. I need to take that token, append it to some parameters stored in a local YAML file, and make the SOAP call to the providers server. If all goes as planned, I need to set session[:credential] to the result of the SOAP call, and forward the user to the root page. Subsequent calls to the before_filter will not make the SOAP call, because session[:credential] is set. Ideally I think this would be awesome to slap on top of Authlogic, but I'm not sure how to do this, So I started to create my own acts_as_soap_authentic plugin, which isn't causing errors, but doesn't do anything.. Anyone have any pointers, or tips as to how I can get the ball rolling here? It seems simple, but is proving not to be..

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• Laggy interface with NSSearchField hooked up to an NSArrayController via bindings

  - by Simone Manganelli

  So I've got an NSSearchField hooked up directly to an NSArrayController via bindings, attached to the filterPredicate, so that without any code, the user can just type in the NSSearchField and filter the list of objects in the NSArrayController presented to him in the interface (an NSCollectionView, to be specific). The NSSearchField is hooked up to provide live searching, so that the NSCollectionView is filtered instantly as the user types, not after waiting for a short period for the user to stop typing. However, the problem is that this makes the interface really laggy. Typing is delayed significantly, by 0.5-1 seconds, and it seems like the NSCollectionView is trying to animate each and every rearrangement of items for each portion of the search string that the user enters. What I'd like is for the searching to be live, but the typing in the search field to be fluid, and the results to filter as fast as possible. Is there a way to do this via bindings, or will I need to put in some custom code that triggers the filterPredicate on a separate thread? (Note that I've got a custom sorting algorithm set up on the NSArrayController, and removing it seems to help a bit with the laggyness, but not completely.)

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• Wondering where to begin

  - by Cat

  Hello all. After being interested for years and years (and years), I have finally decided to start learning how to create software and web applications. Base on recommendations, I have started with learning the basics of web design first (which I am almost done with) and then will move on to the meat of my process: learning the languages. Problem is, I don't know where to start :/ PHP, Ruby, Perl...and where would SQL, JavaScript and .NET fit into the mix? I am assuming they build on each other/play off of each other somewhat so following some sort of 'order' will make the process more logical and digestible. You're probably thinking, "Just go to school for computer engineering, duh!" But I already have a degree and don't plan on going back to school. I believe I have an adequate aptitude for this sort of thing, and although it will be challenging, with the support of the community I know I can do it on my own. Thank in advance everyone and I am very sorry for the length. I look forward to hearing what all you have to say. Warm Regards, Cat

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• Parallel version of loop not faster than serial version

  - by Il-Bhima

  I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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• jQuery DOM manipulation

  - by ufw

  I have different php output in jQuery-based tabs. This output is formed from database and it consists of several <div>'s. Every time I click any tab it sends AJAX request to the php script which performs "SELECT" request and gives result back as response to AJAX request from the tab. $(document).ready(function() { $('ul.tabs li').css('cursor', 'pointer'); $('ul.tabs.tabs1 li').click(function(){ var thisClass = this.className.slice(0,2); $('div.t1').hide(); $('div.t2').hide(); $('div.t3').hide(); $('div.t4').hide(); $('div.' + thisClass).show('fast'); $('ul.tabs.tabs1 li').removeClass('tab-current'); $(this).addClass('tab-current'); var data = thisClass; $.ajax({ type:"GET", url:"handler.php?name="+data, data:data, success:function(html) { $('div.' + thisClass).html(html); } }); return false; }); }); //Server-side PHP script: <?php $name = $_GET[name]; switch ($name) { case "t1": query_and_output_1(); case "t2": query_and_output_2(); // etc... } ?> The problem is that the first tab contains output that must be in second and third ones as well, the second also contains the third tab output. Sorry for such a rubbishy question, I used to work with server side and unfortunately I'm not familiar with DOM and jQuery yet. Thanks.

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• [php] Cookies only changing value every two page refreshes?

  - by Gazillion

  Hello, I'm trying to implement some pixel tracking where I will save certain values in a cookie to then forward users to another page. If users purchase a product after being forwarded to the online store by us the store adds an image tag in the page with our php script included. With the values set in the cookie we would like to track conversions. I understand this tracking technique has some limitations (like if a user has cookies turned off or if they do not load images but that's the direction my client wanted to go in). The problem I'm having is that the cookie's behaviour is extremely... random. I've been trying to track their values (with a var_dump so I don't have to wait for a page reload to view the cookie's value) but it seems the value for one field only gets refreshed every two page reloads. setcookie("tracking[cn]", $cn, time()+3600*24*7,'/','mydomain.com'); setcookie("tracking[t]", $t, time()+3600*24*7,'/','mydomain.com'); setcookie("tracking[kid]", $kid, time()+3600*24*7,'/','mydomain.com'); redirectTo($redirect_url); the values of cn, t are fine but for some reason kid is always wrong (having taken the value of the previous kid) Any help would be extremely appreciated I've been at this all evening! :)

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• django: control json serialization

  - by abolotnov

  Is there a way to control json serialization in django? Simple code below will return serialized object in json: co = Collection.objects.all() c = serializers.serialize('json',co) The json will look similar to this: [ { "pk": 1, "model": "picviewer.collection", "fields": { "urlName": "architecture", "name": "\u0413\u043e\u0440\u043e\u0434 \u0438 \u0430\u0440\u0445\u0438\u0442\u0435\u043a\u0442\u0443\u0440\u0430", "sortOrder": 0 } }, { "pk": 2, "model": "picviewer.collection", "fields": { "urlName": "nature", "name": "\u041f\u0440\u0438\u0440\u043e\u0434\u0430", "sortOrder": 1 } }, { "pk": 3, "model": "picviewer.collection", "fields": { "urlName": "objects", "name": "\u041e\u0431\u044a\u0435\u043a\u0442\u044b \u0438 \u043d\u0430\u0442\u044e\u0440\u043c\u043e\u0440\u0442", "sortOrder": 2 } } ] You can see it's serializing it in a way that you are able to re-create the whole model, shall you want to do this at some point - fair enough, but not very handy for simple JS ajax in my case: I want bring the traffic to minimum and make the whole thing little clearer. What I did is I created a view that passes the object to a .json template and the template will do something like this to generate "nicer" json output: [ {% if collections %} {% for c in collections %} {"id": {{c.id}},"sortOrder": {{c.sortOrder}},"name": "{{c.name}}","urlName": "{{c.urlName}}"}{% if not forloop.last %},{% endif %} {% endfor %} {% endif %} ] This does work and the output is much (?) nicer: [ { "id": 1, "sortOrder": 0, "name": "????? ? ???????????", "urlName": "architecture" }, { "id": 2, "sortOrder": 1, "name": "???????", "urlName": "nature" }, { "id": 3, "sortOrder": 2, "name": "??????? ? ?????????", "urlName": "objects" } ] However, I'm bothered by the fast that my solution uses templates (an extra step in processing and possible performance impact) and it will take manual work to maintain shall I update the model, for example. I'm thinking json generating should be part of the model (correct me if I'm wrong) and done with either native python-json and django implementation but can't figure how to make it strip the bits that I don't want. One more thing - even when I restrict it to a set of fields to serialize, it will keep the id always outside the element container and instead present it as "pk" outside of it.

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• Django + Virtualenv: manage.py commands fail with ImportError of project name.

  - by Bartek

  This is blowing my mind because it's probably an easy solution, but I can't figure out what could be causing this. So I have a new dev box and am setting everything up. I installed virtualenv, created a new environment for my project under ~/.virtualenvs/projectname Then, I cloned my project from github into my projects directory. Nothing fancy here. There are no .pyc files sitting around so it's a clean slate of code. Then, I activated my virtualenv and installed Django via pip. All looks good so far. Then, I run python manage.py syncdb within my project dir. This is where I get confused: ImportError: No module named projectname So I figured I may have had some references of projectname within my code. So I grep (ack, actually) through my code base and I find nothing of the sorts. So now I'm at a loss, given this environment why am I getting an ImportError on a module named projectname that isn't referenced anywhere in my code? I look forward to a solution .. thanks guys!

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• Output is different for R-value and L-value. Why?

  - by Leonid Volnitsky

  Can someone explain to me why output for R-value is different from L-value? #include <iostream> #include <vector> using namespace std; template<typename Ct> struct ct_wrapper { Ct&& ct; // R or L ref explicit ct_wrapper(Ct&& ct) : ct(std::forward<Ct>(ct)) { std::cout << this->ct[1];}; }; int main() { // L-val vector<int> v{1,2,3}; ct_wrapper<vector<int>&> lv(v); cout << endl << lv.ct[0] << lv.ct[1] << lv.ct[2] << endl; // R-val ct_wrapper<vector<int>&&> rv(vector<int>{1,2,3}); cout << endl << rv.ct[0] << rv.ct[1] << rv.ct[2] << endl; } Output (same for gcc48 and clang32): 2 123 2 003

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• Caching issue with javascript and asp.net

  - by Ed Woodcock

  Hi guys: I asked a question a while back on here regarding caching data for a calendar/scheduling web app, and got some good responses. However, I have now decided to change my approach and stat caching the data in javascript. I am directly caching the HTML for each day's column in the calendar grid inside the $('body').data() object, which gives very fast page load times (almost unnoticable). However, problems start to arise when the user requests data that is not yet in the cache. This data is created by the server using an ajax call, so it's asynchronous, and takes about 0.2s per week's data. My current approach is simply to block for 0.5s when the user requests information from the server, and cache 4 weeks either side in the inital page load (and 1 extra week per page change request), however I doubt this is the optimal method. Does anyone have a suggestion as to how to improve the situation? To summarise: Each week takes 0.2s to retrieve from the server, asynchronously. Performance must be as close to real-time as possible. (however the data is not needed to be fully real-time: most appointments are added by the user and so we can re-cache after this) Currently 4 weeks are cached on either side of the inial week loaded: this is not enough. to cache 1 year takes ~ 21s, this is too slow for an initial load.

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• PHP News Feed Database & Design

  - by pws5068

  I'm designing a News Feed system using PHP/MySQL similar to facebook's. I have asked a similar question before but now I've changed the design and I'm looking for feedback. Example News: User_A commented on User_B's new album. "Hey man nice pictures!" User_B added a new Photo to [his/her] profile. [show photo thumbnail] Initially, I implemented this using excessive columns for Obj1:Type1 | Obj2:Type2 | etc.. Now the design is set up using a couple special keywords, and actor/receiver relationships. My database uses a table of messages joined on a table containing userid,actionid,receiverid,receiverObjectTypeID, Here's a condensed version of what it will look like once joined: News_ID | User_ID | Message | Timestamp 2643 A %a commented on %o's new %r. SomeTimestamp 2644 B %a added a new %r to [his/her] profile. SomeTimestamp %a = the User_ID of the person doing the action %r = the receiving object %o = the owner of the receiving object (for example the owner of the album) (NULL if %r is a user) Questions: Is this a smart (efficient/scalable) way to move forward? How can I show messages like: "User_B added 4 new photos to his profile."?

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• how to get access to private members of nested class?

  - by macias

  Background: I have enclosed (parent) class E with nested class N with several instances of N in E. In the enclosed (parent) class I am doing some calculations and I am setting the values for each instance of nested class. Something like this: n1.field1 = ...; n1.field2 = ...; n1.field3 = ...; n2.field1 = ...; ... It is one big eval method (in parent class). My intention is -- since all calculations are in parent class (they cannot be done per nested instance because it would make code more complicated) -- make the setters only available to parent class and getters public. And now there is a problem: when I make the setters private, parent class cannot acces them when I make them public, everybody can change the values and C# does not have friend concept I cannot pass values in constructor because lazy evaluation mechanism is used (so the instances have to be created when referencing them -- I create all objects and the calculation is triggered on demand) I am stuck -- how to do this (limit access up to parent class, no more, no less)? I suspect I'll get answer-question first -- "but why you don't split the evaluation per each field" -- so I answer this by example: how do you calculate min and max value of a collection? In a fast way? The answer is -- in one pass. This is why I have one eval function which does calculations and sets all fields at once.

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• How to publish internal data to the internet - as simple as possible

  - by mlarsen

  We have a .net 2-tier application where a desktop program is talking to a database. We support MS SQL Server 2000, 2005, 2008 and Oracle 9, 10 and 11. The application is sold, not as shrink-wrap, but pretty close. It is quite important for us that the installation and configuration is as easy as possible as installation instructions are usually supplied in written form to the customers internal IT-department. Our application is usually not seen as mission critical for the IT-department, so we need to keep their work down to a minimum. Now we are starting to get wishes for a web application build on top of the same data. The web application will be hosted by us and delivered as a SaaS application. Now the challenge is how to move data back and forth between the web application and the customers internal database. as I see it we have some requirements: We must be ready to handle the situation where the customers database is not accessible from the DMZ. I guess the easiest solution is that all communication is initiated from inside the customers lan. As little firewall configuration as possible. The best is if we can run without any special configuration as long as outgoing traffic from the customers lan are not blocked. If we need something changed in the firewall, we must be able to document that the change is secure. It doesn't have to be real time. Moving data in batches every ten minutes or so is OK. Data moves both ways, but not the same tables, so we don't have to support merges. It would be nice if we don't have to roll our own framework completely. Looking forward to hear your suggestions.

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• WPF closing child- closes parent-window

  - by Thomas Spranger

  i have the pretty same sample as mentioned here. Fast concluded: MainWindow closes when the last childwindow is closed. My Problem: I couldn't solve my problems with the described solutions. I can't produce a program where it als takes place. Only in one of my bigger progs. Maybe someone has an idea or knows any further steps. Thanks for reading - Thomas As requested here's a bit of code: This is the part in the MainWindow: bool editAfterSearch = false; Movie selectedMovie = (Movie)this.listView.SelectedItem; Movie backup = (Movie)selectedMovie.Clone(); if (new OnlineSearchWindow().EditMovieViaOnlineSearch(ref selectedMovie, out editAfterSearch)) { this.coverFlow.Update(selectedMovie); } And that's the part of the ChildWindow: public bool EditMovieViaOnlineSearch(ref Movie preset, out bool editAfter) { this.exitWithOk = false; this.editMovieAfterSearch = false; this.tbx_SearchTerm.Text = preset.Title; this.linkedMovie = preset; this.ShowDialog(); editAfter = editMovieAfterSearch; if (this.exitWithOk) { this.linkedMovie.CloneOnlineInformation(ref preset); preset.Bitmap = this.linkedMovie.Bitmap; return true; } else { return false; } }

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• ArrayAccess multidimensional (un)set?

  - by anomareh

  I have a class implementing ArrayAccess and I'm trying to get it to work with a multidimensional array. exists and get work. set and unset are giving me a problem though. class ArrayTest implements ArrayAccess { private $_arr = array( 'test' => array( 'bar' => 1, 'baz' => 2 ) ); public function offsetExists($name) { return isset($this->_arr[$name]); } public function offsetSet($name, $value) { $this->_arr[$name] = $value; } public function offsetGet($name) { return $this->_arr[$name]; } public function offsetUnset($name) { unset($this->_arr[$name]); } } $arrTest = new ArrayTest(); isset($arrTest['test']['bar']); // Returns TRUE echo $arrTest['test']['baz']; // Echo's 2 unset($arrTest['test']['bar']; // Error $arrTest['test']['bar'] = 5; // Error I know $_arr could just be made public so you could access it directly, but for my implementation it's not desired and is private. The last 2 lines throw an error: Notice: Indirect modification of overloaded element. I know ArrayAccess just generally doesn't work with multidimensional arrays, but is there anyway around this or any somewhat clean implementation that will allow the desired functionality? The best idea I could come up with is using a character as a separator and testing for it in set and unset and acting accordingly. Though this gets really ugly really fast if you're dealing with a variable depth. Does anyone know why exists and get work so as to maybe copy over the functionality? Thanks for any help anyone can offer.

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• nullable bool is being passed to the controller null all the time regardless of the value

  - by user1807954

  I'm trying to pass a nullable bool to my controller. But when I pass the bool value from my view to the controller, it's being passed null all the time regardless of the value it has in my view. Here is my view: @model Cars.Models.Car @using (Html.BeginForm("Index", "Home", FormMethod.Post, new { id = "CategoryFormID"})) { <label>Convertible:</label> <input type="checkbox" id="ConvertibleID" name="convertible"/> <button type="submit" name="submit" value="search" id="SubmitID">Search</button> } And my controller: [HttpPost] public ActionResult Index(bool? convertible){ var cars = from d in db.Car select d; if (convertible.HasValue) { cars = cars.Where(x => x.Convertible == convertible); } return View("SearchResult", cars); } I also have other fields such as drop down lists and text fields, but they're being passed flawless. Any help would be really appreciated. Update: Thank you for your fast responds. However, I did try giving it a value="True" as you guys suggested. There is only 2 options now: null and true. But my intention is to use nullable bool to have three options: null (when user doesn't touch the checkbox), true(checked) and false(unchecked). I know it sounds not smart and silly, but I'm just trying to figure out how nullable bool is working, and what is the intention of having such a thing in C# (I'm new with C#). I was wondering if it is possible to do so with just checkbox and without the use of dropdownlist or radio buttons.

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• .Net long-running scheduled code execution

  - by Prof Plum

  I am working on a couple of projects now where I really wish there was some sort of component that I could specify a time and date, and then execute some sort of method. DateTime date = new DateTime(x,x,x,x,x,x); ScheduledMethod sMethod = new ScheduledMethod(date, [method delegate of some sort]); \\at the specified date, sMethod invokes [method delegate of some sort] I know that I can do this with Windows Workflow Foundation as a long running process, which is good for certain things, but are there any alternatives? Workflow is not exactly straight forward with the details, and it would be nice to be able to deploy something more simple for light weight tasks. An example would be a method that checks a network folder once a day and deletes any files that are more than 30 days old. I realize that this may be pie in the sky dreaming, but this would be extremely useful for automating certain mundane maintinence tasks (scheduled sql operations, file system cleansing, routine email sending, etc.). It does not necessarily have to be .Net, but that is where I am coming from. Any ideas?

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• Project Euler problem 214, How can i make it more efficient?

  - by Once

  I am becoming more and more addicted to the Project Euler problems. However since one week I am stuck with the #214. Here is a short version of the problem: PHI() is Euler's totient function, i.e. for any given integer n, PHI(n)=numbers of k<=n for which gcd(k,n)=1. We can iterate PHI() to create a chain. For example starting from 18: PHI(18)=6 = PHI(6)=2 = PHI(2)=1. So starting from 18 we get a chain of length 4 (18,6,2,1) The problem is to calculate the sum of all primes less than 40e6 which generate a chain of length 25. I built a function that calculates the chain length of any number and I tested it for small values: it works well and fast. sum of all primes<=20 which generate a chain of length 4: 12 sum of all primes<=1000 which generate a chain of length 10: 39383 Unfortunately my algorithm doesn't scale well. When I apply it to the problem, it takes several hours to calculate... so I stop it because the Project Euler problems must be solved in less than one minute. I thought that my prime detection function might be slow so I fed the program with a list of primes <40e6 to avoid the primality test... The code runs now a little bit faster, but there is still no way to get a solution in less than a few hours (and I don't want this). So is there any "magic trick" that I am missing here ? I really don't understand how to be more efficient on this one... I am not asking for the solution, because fighting with optimization is all the fun of Project Euler. However, any small hint that could put me on the right track would be welcome. Thanks !

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• Sequential animations in Jquery

  - by Pickels

  I see a lot people struggling with this(me included). I guess it's mostly due to not perfectly knowing how Javascript scopes work. An image slideshow is a good example of this. So lets say you have series of images, the first one fades in = waits = fades out = next image. When I first created this I was already a little lost. I think the biggest problem for creating the basics is to keep it clean. I noticed working with callbacks can get uggly pretty fast. So to make it even more complicated most slideshows have control buttons. Next, previous, go to img, pause, ... I've been trying this for a while now and this is where I got: $(InitSlideshow); function InitSlideshow() { var img = $("img").hide(); var animate = { wait: undefined, start: function() { img.fadeIn(function() { animate.middle(); }); }, middle: function() { animate.wait = setTimeout(function() { animate.end(); }, 1000); }, end: function() { img.fadeOut(function() { animate.start(); }); }, stop: function() { img.stop(); clearTimeout(animate.wait); } }; $("#btStart").click(animate.start); $("#btStop").click(animate.stop); }; This code works(I think) but I wonder how other people deal with sequentials animations in Jquery? Tips and tricks are most welcome. So are links to good resources dealing with this issue. If this has been asked before I will delete this question. I didn't find a lot of info about this right away. I hope making this community wiki is correct as there is not one correct answer to my question. Kind regards, Pickels

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• I need some pointers on how to implement inertia

  - by gargantaun

  Ok, so I've created a little plugin that takes a bunch of elements and creates a sort of never ending list. I'll try to explain... I have a div, and it's got about 20 elements tags in it. When the user scrolls up, the top element moves out of view and is moved to the bottom of the list. And vice-versa so that when the user scrolls down, the bottom element is moved to the top of the list. This is specifically for Mobile Safari (iPad, iPhone) web content and you can see the work in progress here... http://appliedworks.co.uk/files/times/SVGTests/drumView/drum.html You'll need an iPad or iPhone top see the scrolling in action. You can see the plugin code here... http://appliedworks.co.uk/files/times/SVGTests/drumView/drumView-0.1b.js What I would like to do is implement inertia so the scrolling slows to a halt in response to how fast or slow the user is scrolling when their finger leaves the screen. Just like the inertia commonly found in the iPhone / iPad UI. The problem is, every time an element moves to the top or the bottom of the list, the scollTop value for the parent div is adjusted to make it look like all the elements are staying in the same place. Which means the scrollTop value is never more than the top elements total height. So there's no value I can think of that I can keep on manipulating to give the illusion of inertia. I'm stumped. Does anyone have any suggestions?

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• how to fix error in bitmap size exceeds VM budget

  - by narasimha

  hi folks i am working one application image uploading to sdcard i am scaling that sdcard saved into database some times one error is occurs bitmap size exceeds vm budget ouput : 01-11 15:39:51.809: ERROR/AndroidRuntime(6214): Uncaught handler: thread main exiting due to uncaught exception 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): java.lang.OutOfMemoryError: bitmap size exceeds VM budget 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.graphics.BitmapFactory.nativeDecodeByteArray(Native Method) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.graphics.BitmapFactory.decodeByteArray(BitmapFactory.java:384) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.graphics.BitmapFactory.decodeByteArray(BitmapFactory.java:397) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at com.fitzgeraldsoftware.shout.presentationLayer.Shout.onActivityResult(Shout.java:1653) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.app.Activity.dispatchActivityResult(Activity.java:3624) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.app.ActivityThread.deliverResults(ActivityThread.java:3220) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.app.ActivityThread.handleSendResult(ActivityThread.java:3266) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.app.ActivityThread.access$2600(ActivityThread.java:116) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1823) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.os.Handler.dispatchMessage(Handler.java:99) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.os.Looper.loop(Looper.java:123) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at android.app.ActivityThread.main(ActivityThread.java:4203) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at java.lang.reflect.Method.invokeNative(Native Method) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at java.lang.reflect.Method.invoke(Method.java:521) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 01-11 15:39:51.979: ERROR/AndroidRuntime(6214): at dalvik.system.NativeStart.main(Native Method) how can fix the error please forward some solution thanks in advance

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