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• Optimizing sparse dot-product in C#

  - by Haggai

  Hello. I'm trying to calculate the dot-product of two very sparse associative arrays. The arrays contain an ID and a value, so the calculation should be done only on those IDs that are common to both arrays, e.g. <(1, 0.5), (3, 0.7), (12, 1.3) * <(2, 0.4), (3, 2.3), (12, 4.7) = 0.7*2.3 + 1.3*4.7 . My implementation (call it dict) currently uses Dictionaries, but it is too slow to my taste. double dot_product(IDictionary<int, double> arr1, IDictionary<int, double> arr2) { double res = 0; double val2; foreach (KeyValuePair<int, double> p in arr1) if (arr2.TryGetValue(p.Key, out val2)) res += p.Value * val2; return res; } The full arrays have about 500,000 entries each, while the sparse ones are only tens to hundreds entries each. I did some experiments with toy versions of dot products. First I tried to multiply just two double arrays to see the ultimate speed I can get (let's call this "flat"). Then I tried to change the implementation of the associative array multiplication using an int[] ID array and a double[] values array, walking together on both ID arrays and multiplying when they are equal (let's call this "double"). I then tried to run all three versions with debug or release, with F5 or Ctrl-F5. The results are as follows: debug F5: dict: 5.29s double: 4.18s (79% of dict) flat: 0.99s (19% of dict, 24% of double) debug ^F5: dict: 5.23s double: 4.19s (80% of dict) flat: 0.98s (19% of dict, 23% of double) release F5: dict: 5.29s double: 3.08s (58% of dict) flat: 0.81s (15% of dict, 26% of double) release ^F5: dict: 4.62s double: 1.22s (26% of dict) flat: 0.29s ( 6% of dict, 24% of double) I don't understand these results. Why isn't the dictionary version optimized in release F5 as do the double and flat versions? Why is it only slightly optimized in the release ^F5 version while the other two are heavily optimized? Also, since converting my code into the "double" scheme would mean lots of work - do you have any suggestions how to optimize the dictionary one? Thanks! Haggai

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• How can I access the int values of an object in an NSMutableArray?

  - by Daniel

  I try to access some values in a NSMutableArray I created, but I only get some numbers (address?) if I try to access them. I was able to initialize an array and can add and change objects with [myNSMutableArray addObject:[NSNumber numberWithInt:10]] and [myNSMutableArray replaceObjectAtIndex:0 withObject:[NSNumber numberWithInt:47] I also can print the value at index [0] with NSLog(@"%@", [myNSMutableArray objectAtIndex:0]); and I get 47 as expected. But how can I access the integer value of the object in the array so I can save it tomyIntValue?

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• MySQL indexes - what are the best practises?

  - by Haroldo

  I've been using indexes on my mysql databases for a while now but never properly learnt about them. Generally I put an index on any fields that i will be searching or selecting using a WHERE clause but sometimes it doesn't seem so black and white. What are the best practises for mysql indexes? example situations/dilemas: If a table has six columns and all of them are searchable, should i index all of them or none of them? . What are the negetive performance impacts of indexing? . If i have a VARCHAR 2500 column which is searchable from parts of my site, should i index it?

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• Create Class objects based on type signature

  - by Andreas_D

  Class.forName(boolean.class.getName()); This doesn't work in Java - the virtual machine slaps you with a ClassNotFoundException. I was in need for something like that because I wanted to reflect methods based on Strings that included the method signatures, like public void doSomething(boolean yesWeCan, java.lang.String[] presidents); At the end I came up with a custom 'ClassFactory' which translates the type Strings to class objects. This factory includes a lot of handlers for primitive and array type values. The handler for array type objects is something like: if (isArrayOfObjects) { return Class.forName("L["+typeName.replace("[]", "")+";"); } My question is - have I missed something in the Java 1.5+ API that might do the trick?

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• jQuery - now: Creating an object and storing values in it to pass to an AJAX call

  - by Josh K

  I have an array: myarr = []; I'm filling it with some values: myarray['name'] = "Me!"; Now I want to transform that array into a set of Key = Value pairs. I though jQuery would do it automatically, but it doesn't seem to. $.ajax ({ type: "POST", dataType: "text", url: "myurl", data: myarr }); Is there a way to do this or something I'm doing wrong? I get no javascript errors, and no serverside errors other then no POST information at all. I need the request to be sent as a true POST request. I need to keep the php code simple because sometimes the login won't be an AJAX call. I'm now trying the following with an error unexepected token ':' myarr: { 'name':'me' } The question has now become: How do I initialize a new javascript object as "blank", how do I set up mappings, and how do I pass it in an AJAX call?

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• PHP create page as a string after PHP runs

  - by John

  I'm stuck on how to write the test.php page result (after php has run) to a string: testFunctions.php: <?php function htmlify($html, $format){ if ($format == "print"){ $html = str_replace("<", "&lt;", $html); $html = str_replace(">", "&gt;", $html); $html = str_replace("&nbsp;", "&amp;nbsp;", $html); $html = nl2br($html); return $html; } }; $input = <<<HTML <div style="background color:#959595; width:400px;"> &nbsp;<br> input <b>text</b> <br>&nbsp; </div> HTML; function content($input, $mode){ if ($mode =="display"){ return $input; } else if ($mode =="source"){ return htmlify($input, "print"); }; }; function pagePrint($page){ $a = array( 'file_get_contents' => array($page), 'htmlify' => array($page, "print") ); foreach($a as $func=>$args){ $x = call_user_func_array($func, $args); $page .= $x; } return $page; }; $file = "test.php"; ?> test.php: <?php include "testFunctions.php"; ?> <br><hr>here is the rendered html:<hr> <?php $a = content($input, "display"); echo $a; ?> <br><hr>here is the source code:<hr> <?php $a = content($input, "source"); echo $a; ?> <br><hr>here is the source code of the entire page after the php has been executed:<hr> <div style="margin-left:40px; background-color:#ebebeb;"> <?php $a = pagePrint($file); echo $a; ?> </div> I'd like to keep all the php in the testFunctions.php file, so I can place simple function calls into templates for html emails. Thanks!

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• jquery dynamically genearate element id in a loop

  - by phil

  This is a loop in a function intending to create elements <li> and give each <li> an unique id. But it's not working. I suspect it's a simple syntax error with the use of quote in .attr(). But I can't get a straight answer from Google. for (i=0;i<array.length;i++) { //create HTML element of tag li $('#suggest').append("<li></li>"); $("li").attr("id",'li'+i); $('#li'+i).html(array[i]); }

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• Is scala functional programming slower than traditional coding?

  - by Fred Haslam

  In one of my first attempts to create functional code, I ran into a performance issue. I started with a common task - multiply the elements of two arrays and sum up the results: var first:Array[Float] ... var second:Array[Float] ... var sum=0f; for(ix<-0 until first.length) sum += first(ix) * second(ix); Here is how I reformed the work: sum = first.zip(second).map{ case (a,b) => a*b }.reduceLeft(_+_) When I benchmarked the two approaches, the second method takes 40 times as long to complete! Why does the second method take so much longer? How can I reform the work to be both speed efficient and use functional programming style?

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• How to find Key and IV value from .Net to PHP

  - by PHP-Prabhu

  Can any one please let me know is there any way to find a solution for the below stuffs. I need to find out the KEY and IV value from the below byte array. the byte array in .net and this has to be convert into KEY(string) and IV(string) via PHP. private static readonly byte[] Key = { 0xda, 0x3c, 0x35, 0x6f, 0xbd, 0xd, 0x87, 0xf0, 0x9a, 0x7, 0x6d, 0xab, 0x7e, 0x82, 0x36, 0xa, 0x1a, 0x5a, 0x77, 0xfe, 0x74, 0xf3, 0x7f, 0xa8, 0xaa, 0x4, 0x11, 0x46, 0x6b, 0x2d, 0x48, 0xa1 }; private static readonly byte[] IV = { 0x6d, 0x2d, 0xf5, 0x34, 0xc7, 0x60, 0xc5, 0x33, 0xe2, 0xa3, 0xd7, 0xc3, 0xf3, 0x39, 0xf2, 0x16 };

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• Ruby methods within Javascript within HAML

  - by Josh

  I have a jQuery script that adds a new field to a form, and this field contains dynamic information from an array. The problem is that I can't figure out how to add an array.each to populate the options of the select field within the javascript without breaking the HAML indentation and causing errors. Here is my best attempt that does not work: %script(type="text/javascript") $('#mylink').click(function() { $('#mylink').after('<select> - myarray.each do |options| <option value="#{options.id}">#{options.name}</option> </select>); )}; Also tried it with the :javascript filter with no luck. EDIT: For whatever reason, I can't get the 4-space indents ( for Markdown ) working here, but I do have it indented properly.

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• JavaScript BubbleSort

  - by Alyn

  Hi, Have a bubblesort routine similar the this. I need to make it more efficient by stopping the loop when the array is sorted or if the array is already sorted. function sortNumbers(listbox) { var x, y, holder; // The Bubble Sort method. for(x = 0; x < ranarray.length; x++) { for(y = 0; y < (ranarray.length-1); y++) { if(ranarray[y] > ranarray[y+1]) { holder = ranarray[y+1]; ranarray[y+1] = ranarray[y]; ranarray[y] = holder; } } }

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• filter functions problem

  - by Adam

  I'm working on a search component for an app I'm working on and I needed to add some filters to it. I've found an example and got the first filter working fine. Now I'm trying to add a second filter I'm running into problems... In the example I found they use filterFunctions, but I only get an option for filterFunction, why is that? Here's the example code productsCollection.filterFunctions = [ filterByPrice, filterByType, filterByCondition, filterByVendor ] And this is what I'm trying acData.filterFunction = [filterByStatus, filterByDate] but with this code I get the following error message - 1067: Implicit coercion of a value of type Array to an unrelated type Function. Why am I getting this error and how would I go about add multiple filters to my Array Collection? Thanks!

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• Recommended place for pre-translated Zend Framework resources

  - by Exception e

  Since zf 1.10 Zend Framework ships with pre-translated validation messages. They are outside the library path. The manual illustrates how to load these in your bootstrap. $translator = new Zend_Translate( 'array', '/resources/languages', $language, array('scan' => Zend_Locale::LOCALE_DIRECTORY) ); Zend_Validate_Abstract::setDefaultTranslator($translator); I am inclined to think that these resources are specific to the zf-version; validators could change over time. If i copy the resources to my application tree I need to perform additional maintenance each time I upgrade to a newer version. What is best practice? Is there a ZF convention already?

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• embed multiple youtube videos to chromeless player cue

  - by Quaze

  So in the project ive been working on i use the youtube API to add a video to a chromeless player (got custom buttons, everything works no problems). It loads the youtube id which it gets from the database (Codeigniter, PHP). But what i would like to see is: instead of loading 1 video, id like to add all the videos i get from the database in the cue of that one player. So only one screen, first video retrieved from dbase gets played first, when its done second get loaded preferably also looped. Is there any way i can achieve this? My first guess would be to save the array with youtube id's somewhere and on state change (when the 'video stop'-event gets fired) load the next id from the array. Havent tried this yet because id prefer if the cue gets just gets filled on the init, so it doesnt have to load after a video has been ended. Is This possible?

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• Javascript function programming — receiving elaborate parameters

  - by Barney

  I'm writing a Javascript function that would manipulate an array written on-the-fly and sent as a parameter. The function is written as follows: function returnJourney(animation,clean){ var properties = {}; // loads of other inane stuff for(i in animation[0]) properties[animation[0][i]] = animation[0].i; // heaps more inane stuff } The animation in question is a set of parameters for a jQuery animation. Typically it takes the format of ({key:value,key:value},speedAsInteger,modifierAsString). So to kick off initial debugging I call it with: returnJouney(({'foo':'bar'},3000),1); And straight off the bat things are way off. As far as I see it this would have returnJourney acknowledge clean === 1, and animation being an array with an object as its first child and the number 3000 as its second. Firebug tells me animation evaluates as the number 3000. What am I doing wrong?

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• Overloaded function print

  - by Olga Shirokova

  For one of the assignments I need to create an overloaded function print that prints an element or all elements of an array. I have no problem with printing the entire array: for( int i = 0; i < size; i++) cout << list [ i ] <<endl; But how do I make the same function to print only one particular element? The way I see it is to ask a user what to print, either one element or all numbers. Or am I missing something here?

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• c# im getting an error

  - by vj4u

  double dval = 1; for (int i = 0; i < Cols; i++) { k = 0; dval = 1; for (int j = Cols - 1; j >= 0; j--) { colIndex = (i + j) % 3; val *= dval[colIndex, k]; k++; } det -= dval; } im getting an error Cannot apply indexing with [] to an expression of type 'double' for dval help its urgent

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• convert std object class to comma seperated string

  - by Kwaasi Djin

  I have an std class object from twitter and i would like to take the ids array values and put them in a php variable $ids where $ids = (15761916,30144785,382747195,19399719). I imagine using a for loop and using phps implode but i'm not sure how to go about it. stdClass Object ( [ids] => Array ( [0] => 15761916 [1] => 30144785 [2] => 382747195 [3] => 19399719 ) [next_cursor] => 0 [next_cursor_str] => 0 [previous_cursor] => 0 [previous_cursor_str] => 0 )

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• How do I change the background image of my iPhone app?

  - by alJaree

  Hello I have looked around and found some code which so called chooses an image from an array of image objects, but cant find an explanation. I would like to make my app have a background image and the user can select next and previous buttons to scroll through some full screen images, setting them as the background image as they scroll. I know how to do this in java, but cant seem to do it for this app. How or what code is linked to a next button to grab the next image in the array and reverse for the back button? Then that needs to be displayed obviously. I have used a layered architecture with a MVC style approach but cant seem to put it together with Objective-C. Would the buttons call the appropriate methods of the so called delegates, which the delegates handle fetching and returning the Images? Would the buttons use the returned images and actually handle the redrawing? I would really appreciate the help. Regards Jarryd

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• No optimization causes wrong search result

  - by KailZhang

  I just took over our solr/lucene stuff from my ex-colleague. But there is a weird bug. If there is no optimization after dataimport, actually if there are multiple segment files, the search result then will be wrong. We are using a customized solr searchComponent. As far as I know about lucene, optimization is only optimization which could improve the speed of indexing and should not affect search result. I doubt this may be related to multithreading or unclosed searcher/reader or something. Anybody can help? Thank you.

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• Cakephp: Access data in add function

  - by Chris

  I'm using the CakePHP blog example: function add() { if (!empty($this->data)) { if ($this->Post->saveAll($this->data)) { $this->Session->setFlash('Your post has been saved.'); $this->redirect(array('action' => 'index')); } }} I want to modify it in a way that the user is redirected to the post after adding it: But this doesn't work: $this->redirect(array('action' => 'view', $this->Post->id))); What is the correct way to read the model's data after creation?

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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• symfony 1.4 embedForm not returning all embedded forms

  - by Patrick

  I have a form with multiple embedded forms and symfony is not binding all the embedded forms. The layout is a m-to-m layout: activity: id: link: id: activity_id: FOREIGN KEY to activity table other_data_id: FOREIGN KEY to other_data table other_data: id: For instance I have 7 identical embedded forms iterated at the end of each name (ie- form_1, form_2, ..., form_7). With the new and edit forms all the 7 fields display properly, but when I submit the form, the embedded forms after a certain number just aren't in the embedded forms array of the sfForm. I have two different embedded forms, the first form stops binding at 5 and the second form stops binding at 4. I've looked at the array of posted values through $request->getPostParameters(); and all the fields are there. If I manually enter the data into the database, the binding works without a problem. Any ideas would be greatly appreciated!

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• How do I write a writer method for a class variable in Ruby?

  - by tepidsam

  I'm studying Ruby and my brain just froze. In the following code, how would I write the class writer method for 'self.total_people'? I'm trying to 'count' the number of instances of the class 'Person'. class Person attr_accessor :name, :age @@nationalities = ['French', 'American', 'Colombian', 'Japanese', 'Russian', 'Peruvian'] @@current_people = [] @@total_people = 0 def self.nationalities #reader @@nationalities end def self.nationalities=(array=[]) #writer @@nationalities = array end def self.current_people #reader @@current_people end def self.total_people #reader @@total_people end def self.total_people #writer #-----????? end def self.create_with_attributes(name, age) person = self.new(name) person.age = age person.name = name return person end def initialize(name="Bob", age=0) @name = name @age = age puts "A new person has been instantiated." @@total_people =+ 1 @@current_people << self end

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• Specify fields in a recursive find with cakephp

  - by Razor Storm

  Suppose I have a table Recipe that hasmany ingredients. I do a recursive find to grab recipes with their associated ingredients: $this->Recipe->find('all', array('fields' => array('id','title','description'))); Here I can use the 'fields' attribute to specify that I only want it to return id, title, and description. However, despite this, cakephp still returns ALL columns from the ingredients table. How do I tell cakephp that I only want ingredient table's id and name fields? btw ingredient model is "Ingredient" and the table is ingredients, and the aggregation table is recipes_ingredients.

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