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  • Shuffle Two NSMutableArray independently

    - by Superman
    I'm creating two NSMutableArray in my viewDidLoad, I add it in a NSMutableDictionary. When I tried shuffling it with one array, It is okay. But the problem is when Im shuffling two arrays independently its not working,somehow the indexes got mixed up. Here is my code for my array (I have two of these): self.items1 = [NSMutableArray new]; for(int i = 0; i <= 100; i++) { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); NSString *documentsDir = [paths objectAtIndex:0]; NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"[Images%d.png", i]]; if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){ self.container = [[NSMutableDictionary alloc] init]; [container setObject:[UIImage imageWithContentsOfFile:savedImagePath] forKey:@"items1"]; [container setObject:[NSNumber numberWithInt:i] forKey:@"index1"]; [items1 addObject:container]; } } NSLog(@"Count : %d", [items1 count]); [items1 enumerateObjectsUsingBlock:^(id object, NSUInteger index, BOOL *stop) { NSLog(@"%@ images at index %d", object, index); }]; then my shuffle code(Which I tried duplicating for the other array,but not working also): srandom(time(NULL)); NSUInteger count = [items1 count]; for (NSUInteger i = 0; i < count; ++i) { int nElements = count - i; int n = (random() % nElements) + i; [items1 exchangeObjectAtIndex:i withObjectAtIndex:n]; } How am I going to shuffle it using above code (or if you have other suggestions) with two arrays? Thanks My other problem is when I tries subclassing the class for the shuffle method or either use the above code, their index mixed. For example: Object: apple, ball, carrots, dog Indexes: 1 2 3 4 but in my View when shuffled: Object: carrots, apple, dog, balle Indexes: 2 4 1 3

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  • Core Data Change property value when another property changes

    - by user320587
    Hi, I have a Core Data Entity which has three properties startDate, endDate and duration. All three properties are persistent properties. I would like to know how I can calculate and update the duration property whenever the value for startDate and endDate changes? BTW, I won't be able to make the duration as transient property since I have to use the property for sorting in my table view? Any help is greatly appreciated Thanks, Javid

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  • How to speed-up python nested loop?

    - by erich
    I'm performing a nested loop in python that is included below. This serves as a basic way of searching through existing financial time series and looking for periods in the time series that match certain characteristics. In this case there are two separate, equally sized, arrays representing the 'close' (i.e. the price of an asset) and the 'volume' (i.e. the amount of the asset that was exchanged over the period). For each period in time I would like to look forward at all future intervals with lengths between 1 and INTERVAL_LENGTH and see if any of those intervals have characteristics that match my search (in this case the ratio of the close values is greater than 1.0001 and less than 1.5 and the summed volume is greater than 100). My understanding is that one of the major reasons for the speedup when using NumPy is that the interpreter doesn't need to type-check the operands each time it evaluates something so long as you're operating on the array as a whole (e.g. numpy_array * 2), but obviously the code below is not taking advantage of that. Is there a way to replace the internal loop with some kind of window function which could result in a speedup, or any other way using numpy/scipy to speed this up substantially in native python? Alternatively, is there a better way to do this in general (e.g. will it be much faster to write this loop in C++ and use weave)? ARRAY_LENGTH = 500000 INTERVAL_LENGTH = 15 close = np.array( xrange(ARRAY_LENGTH) ) volume = np.array( xrange(ARRAY_LENGTH) ) close, volume = close.astype('float64'), volume.astype('float64') results = [] for i in xrange(len(close) - INTERVAL_LENGTH): for j in xrange(i+1, i+INTERVAL_LENGTH): ret = close[j] / close[i] vol = sum( volume[i+1:j+1] ) if ret > 1.0001 and ret < 1.5 and vol > 100: results.append( [i, j, ret, vol] ) print results

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  • The question about the basics of LINQ to SQL working

    - by Alex
    I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer Get all customers from the database ("SELECT * FROM Customers"), move them to the Customers array and then make a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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  • Weird compile-time behavior when trying to use primitive type in generics

    - by polygenelubricants
    import java.lang.reflect.Array; public class PrimitiveArrayGeneric { static <T> T[] genericArrayNewInstance(Class<T> componentType) { return (T[]) Array.newInstance(componentType, 0); } public static void main(String args[]) { int[] intArray; Integer[] integerArray; intArray = (int[]) Array.newInstance(int.class, 0); // Okay! integerArray = genericArrayNewInstance(Integer.class); // Okay! intArray = genericArrayNewInstance(int.class); // Compile time error: // cannot convert from Integer[] to int[] integerArray = genericArrayNewInstance(int.class); // Run time error: // ClassCastException: [I cannot be cast to [Ljava.lang.Object; } } I'm trying to fully understand how generics works in Java. Things get a bit weird for me in the 3rd assignment in the above snippet: the compiler is complaining that Integer[] cannot be converted to int[]. The statement is 100% true, of course, but I'm wondering WHY the compiler is making this complaint. If you comment that line, and follow the compiler's "suggestion" as in the 4th assignment, the compiler is actually satisfied!!! NOW the code compiles just fine! Which is crazy, of course, since like the run time behavior suggests, int[] cannot be converted to Object[] (which is what T[] is type-erased into at run time). So my question is: why is the compiler "suggesting" that I assign to Integer[] instead for the 3rd assignment? How does the compiler reason to arrive to that (erroneous!) conclusion?

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  • Java Swing - Adding a row # column (row header) to a JTable

    - by llm
    I have data from a database loaded into a JTable through a custom table model. I want to have a column (should be the first column) which simply shows the display row number (i.e. it is not tied to any data (or sorting) but is simply the row number on the screen starting at 1). These "row headers" should be grayed out like the row headers. Any idea how to do this? Thanks

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  • Web Programming language for very large lists?

    - by behrk2
    Hello, In your experience, what is the best web programming language used to handle sorting and comparison of very large lists (ie tens of thousands of email addresses)? I am most familiar with PHP. I think that it could get the job done, but I'm unsure of other languages and if there might be a bettor suitor. Thanks!

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  • NSMutableArray memory management

    - by chicken
    NSMutableArray *a1 = [[NSMutableArray alloc] init]; NSMutableArray *a2 = [NSMutableArray array]; TempObj *obj = [[TempObj alloc] init]; //assume this line is repeated for each obj [a1 addObject:obj]; [a1 addObject:obj2]; [a1 addObject:obj3]; [a1 addObject:obj4]; [obj release]; [obj2 release]; [obj3 release]; [obj4 release]; [a1 release]; Ok so a2 is an autorelease obj so i dont have to call release on it? Also how do you know when you get an autorelease object? And for a1, i dont have to loop through the array and release each object first? What if i called [a1 removeAllObjects]; does that call [[a1 objectAtIndex:#] release]; Am i supposed to release those objects after ive added them to the array?

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  • reading a file of unknown length with a function

    - by Faken
    I'm trying to write a short function that will let me quickly read in a file of unknown size and return pointer to the array of data and the length of that array but it seems my code isn't working. What am i doing wrong? int readIn(int* pointer, param parameters, string description) { string fileName = parameters.fileName + " " + description + ".bin"; ifstream readFile; readFile.open(fileName.c_str(), ios::in|ios::binary|ios::ate); int size = readFile.tellg(); int length = size / 4; int* output = new int [length]; readFile.seekg (0, ios::beg); readFile.read(reinterpret_cast<char*>(output), (size)); readFile.close(); pointer = output; // link new array with the pointer return length; } and in the main function: int* testList; int numEntries = readIn(testList, parameters, "test"); I end up with an error saying that my testList variable was used and not initialized. What am i doing wrong?

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  • PHP for loop isn't looping after APC installation

    - by BoRo
    So I installed APC and i all of the sudden my for loops only run once and increment the value then stops. I dont get what's going on, it worked fine before APC was installed. Any Suggestions? EDIT: I managed to narrow it down to the increment. for some reason if I have an array let's say string[], and have the for loop list through the values like with string[$i] It only does it for the first one, I can manually echo/print out the array elements to check if the array is the problem but all elements have the appropriate data/values. EDIT #2: Well the code looks something like (it scrapes a page for images and gets some data from it): $str = explode('<div class="images" align="center">',$str); for($i=1;$i<11;$i++){ $url3 = $str[$i]; $url3 = extstr3($url3,'class="filename">','</div>'); $urlname = extstr3($url3,'<a href="','</a>'); $name = extstr3($urlname,'target="_blank">','.jpg'); $url3 = extstr3($url3,'<a href="','" target="_blank">'); $name = str_replace ('_', ' ', $name); . . .

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  • Google Calendar feed api deleted events

    - by hsmit
    I'm syncing the Google Calendar with my application (I store events in a database). When an event is updated I can easily find the last updates by sorting the event feed on the 'updated' order. However, if an event is removed / deleted, how can I track this update from the feed?

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  • Postgresql count+sort performance

    - by invictus
    I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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  • Create a multicolor selectbox on Symfony2

    - by Ninsuo
    I try to create the following field : <select name="test"> <option value="1">a</option> <option value="2">b</option> <option value="3" style="font-weight: bold; color: red;">c</option> <option value="4">d</option> <option value="5">e</option> </select> This creates a 2-color selectbox : But in Symfony2, I do not know how to apply a class to a single option. If in my view I do : {{ form_widget(myForm.test, { 'attr': { 'class': 'red', } }) }} Or if in my form I do : $builder->add('test', 'choice', array( 'required' => true, 'choices' => array('a', 'b', 'c', 'd', 'e'), 'attr' => array('class' => 'red'), )); The attribute is stored into the <select> tag and apply to the whole selectable values. How do I apply a class to an <option> in Symfony2 ?

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  • C - dns query to structure

    - by Bibo
    I have these structures: typedef struct dnsQuery { char header[12]; struct dnsQuerySection *querySection; } TdnsQuery; typedef struct dnsQuerySection { unsigned char *name; struct dnsQueryQuestion *question; } TdnsQuerySection; typedef struct dnsQueryQuestion { unsigned short qtype; unsigned short qclass; } TdnsQueryQuestion; and I have dns query in byte array from recvfrom. I am trying to get structure from byte array like this: TdnsQuery* dnsQuery = (TdnsQuery*)buf; When I tried to access qtype like this: printf("%u", dnsQuery->querySection->question.qtype); I get seg fault 11. Can someone help me with these structures? What´s wrong with them? I tried to add structure: typedef struct udpPacket { char header[8]; structr dnsQuery query; } and mapped this structure from byte array but it didn´t help. Can someone help me with these structures? How they should look like for dns query with udp protocol?

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  • parse string with regular exression

    - by llamerr
    I trying to parse this string: $right = '34601)S(1,6)[2] - 34601)(11)[2] + 34601)(3)[2,4]'; with following regexp: const word = '(\d{3}\d{2}\)S{0,1}\([^\)]*\)S{0,1}\[[^\]]*\])'; preg_match('/'.word.'{1}(?:\s{1}([+-]{1})\s{1}'.word.'){0,}/', $right, $matches); print_r($matches); i want to return array like this: Array ( [0] => 34601)S(1,6)[2] - 34601)(11)[2] + 34601)(3)[2,4] [1] => 34601)S(1,6)[2] [2] => - [3] => 34601)(11)[2] [4] => + [5] => 34601)(3)[2,4] ) but i return only following: Array ( [0] => 34601)S(1,6)[2] - 34601)(11)[2] + 34601)(3)[2,4] [1] => 34601)S(1,6)[2] [2] => + [3] => 34601)(3)[2,4] ) i think, its becouse of [^)]* or [^]]* in the word, but how i should correct regexp for matching this in another way? i tryied to specify it: \d+(?:[,#]\d+){0,} so word become const word = '(\d{3}\d{2}\)S{0,1}\(\d+(?:[,#]\d+){0,}\)S{0,1}\[\d+(?:[,#]\d+){0,}\])'; but it gives nothing

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  • Is DOM not being loaded ?

    - by Daniel
    I went through episode 88 (Dynamic menus) of the railscasts and when I try to load my *js.erb file in the browser shows me that my fetched data from the controller is getting there Controller def dynamic_departments @departments = Department.all end localhost:3000/javascripts/dynamic_departments.js var departments = new Array(); departments.push(new Array(1,'????',1)); departments.push(new Array(2,'???-???',2)); function facultySelected(){ faculty_id = $('falculty_id').getValue(); options = $('department_id').options; options.length = 1; departments.each(function(department){ if(department[0] == faculty_id){ options[options.length] = new Option(department[1],department[2]) } }); if(options.length == 1){ $('department_field').hide(); } else { $('department_field').show(); } } document.observe('dom:loaded', function(){ alert("DOM loaded"); //$('department_field').hide(); //$('faculty_id').observe('change',facultySelected); }); My routes.rb has the match ':controller/:action.:format' Still...after the page's loaded and I change the value of my collection_select or select nothing happens.What am I missing? *I called the 'alert' and commented the rest to test it....still nothing.

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  • Is there a better way to change user password in cakephp using Auth?

    - by sipiatti
    Hi, I am learning cakephp by myself. I tried to create a user controller with a changepassword function. It works, but I am not sure if this is the best way, and I could not googled up useful tutorials on this. Here is my code: class UsersController extends AppController { var $name = 'Users'; function login() { } function logout() { $this->redirect($this->Auth->logout()); } function changepassword() { $session=$this->Session->read(); $id=$session['Auth']['User']['id']; $user=$this->User->find('first',array('conditions' => array('id' => $id))); $this->set('user',$user); if (!empty($this->data)) { if ($this->Auth->password($this->data['User']['password'])==$user['User']['password']) { if ($this->data['User']['passwordn']==$this->data['User']['password2']) { // Passwords match, continue processing $data=$this->data; $this->data=$user; $this->data['User']['password']=$this->Auth->password($data['User']['passwordn']); $this->User->id=$id; $this->User->save($this->data); $this->Session->setFlash('Password changed.'); $this->redirect(array('controller'=>'Toners','action' => 'index')); } else { $this->Session->setFlash('New passwords differ.'); } } else { $this->Session->setFlash('Typed passwords did not match.'); } } } } password is the old password, passwordn is the new one, password2 is the new one retyped. Is there any other, more coomon way to do it in cake?

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  • Ruby shortest way to write rnd hex

    - by Whirlwin
    Hi. What I have is a method used to generate random hex values. E.g 666 or FF7 However, I don't think it looks simple/elegant at all.. What I want is to make it more simple which perhaps will make my code shorter as well, but I don't know how. That is why I need tips or hints Here is my code so far: def random_values random_values = Array.new letters = ['A','B','C','D','E','F'] for i in 1..15 if i <= 9 random_values << i else random_values << letters[i-10] end end return random_values.shuffle[0].to_s + random_values.shuffle[0].to_s + random_values.shuffle[0].to_s end As you probably see, I do not generate random numbers. I just shuffle the array containing the values I want, meaning all the numbers in the array are unique, which is not needed, but was the easiest solution for me when I wrote the code. I am most concerned about the return line.. If only it was possible to write like: return 3.times { random_values.shuffle[0] } or return random_values.shuffle[0].to_s *3 Thanks in advance!

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  • How to create a generic method in C# that's all applicable to many types - ints, strings, doubles et

    - by satyajit
    Let's I have a method to remove duplicates in an integer Array public int[] RemoveDuplicates(int[] elems) { HashSet<int> uniques = new HashSet<int>(); foreach (int item in elems) uniques.Add(item); elems = new int[uniques.Count]; int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } How can I make this generic such that now it accepts a string array and remove duplicates in it? How about a double array? I know I am probably mixing things here in between primitive and value types. For your reference the following code won't compile public List<T> RemoveDuplicates(List<T> elems) { HashSet<T> uniques = new HashSet<T>(); foreach (var item in elems) uniques.Add(item); elems = new List<T>(); int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } The reason is that all generic types should be closed at run time. Thanks for you comments

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  • Cannot pass null to server using jQuery AJAX. Value received at the server is the string "null".

    - by Tom
    I am converting a javascript/php/ajax application to use jQuery to ensure compatibility with browsers other than Firefox. I am having trouble passing true, false, and null values using jQuery's ajax function. Javascript code: $.ajax ( { url : <server_url>, dataType: 'json', type : 'POST', success : receiveAjaxMessage, data: { valueTrue : true, valueFalse : false, valueNull : null } } ); PHP code: var_dump($_POST); Server output: array(3) { ["valueTrue"]=> string(4) "true" ["valueFalse"]=> string(5) "false" ["valueNull"]=> string(4) "null" } The problem is that the null, true, and false values are being converted to strings. The Javascript AJAX code currently in use passes null, true, and false correctly but only works in Firefox. Does anyone know how to solve this problem using jQuery? Here is some working code (not using jQuery) to compare with the code not-working code given above. Javascript Code: ajaxPort.send ( <server_url>, { valueTrue : true, valueFalse : false, valueNull : null } ); PHP code: var_dump(json_decode(file_get_contents('php://input'), true)); Server output: array(3) { ["valueTrue"]=> bool(true) ["valueFalse"]=> bool(false) ["valueNull"]=> NULL } Note that the null, true, and false values are correctly received. Note also that in the second method the $_POST array is not used in the PHP code. I think this is the key to the problem, but I cannot find a way to replicate this behavior using jQuery.

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  • efficient sort with custom comparison, but no callback function

    - by rob
    I have a need for an efficient sort that doesn't have a callback, but is as customizable as using qsort(). What I want is for it to work like an iterator, where it continuously calls into the sort API in a loop until it is done, doing the comparison in the loop rather than off in a callback function. This way the custom comparison is local to the calling function (and therefore has access to local variables, is potentially more efficient, etc). I have implemented this for an inefficient selection sort, but need it to be efficient, so prefer a quick sort derivative. Has anyone done anything like this? I tried to do it for quick sort, but trying to turn the algorithm inside out hurt my brain too much. Below is how it might look in use. // the array of data we are sorting MyData array[5000], *firstP, *secondP; // (assume data is filled in) Sorter sorter; // initialize sorter int result = sortInit (&sorter, array, 5000, (void **)&firstP, (void **)&secondP, sizeof(MyData)); // loop until complete while (sortIteration (&sorter, result) == 0) { // here's where we do the custom comparison...here we // just sort by member "value" but we could do anything result = firstP->value - secondP->value; }

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  • Cakephp cache only caching one file per action

    - by Jamesz
    Hi, I have a songs controller. Within the songs controller i have a 'view' action which get's passed an id, eg /songs/view/1 /songs/view/5 /songs/view/500 When a user visits /songs/view/1, the file is cached correctly and saved as 'songs_view_1.php' Now for the problem, when a user hit's a different song, eg /songs/view/2, the 'songs_view_1.php' is deleted and '/songs/view/2.php' is in it's place. The cahced files will stay there for a day if I don't visit a different url, and visiting a different action will not affect any other action's cached file. I've tried replacing my 'cake' folder (from 1.2 to 1.2.6), but that didn't do anything. I get no error messages at all and nothing in the logs. Here's my code, I've tried umpteen variations all ending up with the same problem. var $helpers = array('Cache'); var $cacheAction = array( 'view/' => '+1 day' ); Any ideas? EDIT: After some more testing, this code var $cacheAction = array( 'view/1' => "1 day", 'view/2' => "1 day" ); will cache 'view/1' or 'view/2', but delete the previous page as before. If I visit '/view/3' it will delete the cached page from before... sigh EDIT: Having the same issue on another server with same code...

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  • Multithreaded linked list traversal

    - by Rob Bryce
    Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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  • Boost threading/mutexs, why does this work?

    - by Flamewires
    Code: #include <iostream> #include "stdafx.h" #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> using namespace std; boost::mutex mut; double results[10]; void doubler(int x) { //boost::mutex::scoped_lock lck(mut); results[x] = x*2; } int _tmain(int argc, _TCHAR* argv[]) { boost::thread_group thds; for (int x = 10; x>0; x--) { boost::thread *Thread = new boost::thread(&doubler, x); thds.add_thread(Thread); } thds.join_all(); for (int x = 0; x<10; x++) { cout << results[x] << endl; } return 0; } Output: 0 2 4 6 8 10 12 14 16 18 Press any key to continue . . . So...my question is why does this work(as far as i can tell, i ran it about 20 times), producing the above output, even with the locking commented out? I thought the general idea was: in each thread: calculate 2*x copy results to CPU register(s) store calculation in correct part of array copy results back to main(shared) memory I would think that under all but perfect conditions this would result in some part of the results array having 0 values. Is it only copying the required double of the array to a cpu register? Or is it just too short of a calculation to get preempted before it writes the result back to ram? Thanks.

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  • jQuery indexOf select box manipulation

    - by kenny99
    Hi, I'm trying to figure out how to remove options from a select box when that option has been selected in an adjacent select box. Basically the user has the option to add multiple records here via select boxes, but I want to remove the list of options available to them so that, for example, they can't enter the same value in two select boxes. When an Add More button is clicked, I fade in the next select box container. A number of select boxes have been generated by PHP and I use JS to hide them. Each select box has a unique number appended to the ID, so i want to access those select boxes which contain the string "other_pet_types", then I want to iterate through the currently visible ones and build an array of the values which have been selected, which I will then remove from the list of options in the newly displayed select box. This is what I have so far, but it's definitely not right - I can't get the initial test on the ID to work. Any pointers greatly appreciated as i realise i'm pretty wide of the mark at the moment! var vals = new Array(); //build array with currently selected options $('p.mult_entries select').each(function(){ vals += $(this).val(); }); $("p.mult_entries:hidden:first").fadeIn("slow", function() { $(this).find(('select').attr('id').indexOf('other_pet_types') > 0).each(function(){ console.log($(this).val()); //as expected prints nothing - need to iterate through the options of the above select //once i extract the correct values, iterate through new select box and use inArray to remove options where that value already exists in one of previous select boxes }); });

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