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• ublas::bounded_vector<> being resized?

  - by n2liquid

  Now, seriously... I'll refrain from using bad words here because we're talking about the Boost fellows. It MUST be my mistake to see things this way, but I can't understand why, so I'll ask it here; maybe someone can enlighten me in this matter. Here it goes: uBLAS has this nice class template called bounded_vector<> that's used to create fixed-size vectors (or so I thought). From the Effective uBLAS wiki (http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?Effective_UBLAS): The default uBLAS vector and matrix types are of variable size. Many linear algebra problems involve vectors with fixed size. 2 and 3 elements are common in geometry! Fixed size storage (akin to C arrays) can be implemented efficiently as it does not involve the overheads (heap management) associated with dynamic storage. uBLAS implements fixed sizes by changing the underling storage of a vector/matrix to a "bounded_array" from the default "unbounded_array". Alright, this bounded_vector<> thing is used to free you from specifying the underlying storage of the vector to a bounded_array<> of the specified size. Here I ask you: doesn't it look like this bounded vector thing has fixed size to you? Well, it doesn't have. At first I felt betrayed by the wiki, but then I reconsidered the meaning of "bounded" and I think I can let it pass. But in case you, like me (I'm still uncertain), is still wondering if this makes sense, what I found out is that the bounded_vector<> actually can be resized, it may only not be greater than the size specified as template parameter. So, first off, do you think they've had a good reason not to make a real fixed<< size vector or matrix type? Do you think it's okay to "sell" this bounded -- as opposed to fixed-size -- vector to the users of my library as a "fixed-size" vector replacement, even named "Vector3" or "Vector2", like the Effective uBLAS wiki did? Do you think I should somehow implement a vector with fixed size for this purpose? If so, how? (Sorry, but I'm really new to uBLAS; just tried it today) I am developing a 3D game. Should uBLAS be used for the calculations involved in this ("hey, geometry!", per Effective uBLAS wiki)? What replacement would you suggest, if not? -- edit And just in case, yes, I've read this warning: It should be noted that this only changes the storage uBLAS uses for the vector3. uBLAS will still use all the same algorithm (which assume a variable size) to manipulate the vector3. In practice this seems to have no negative impact on speed. The above runs just as quickly as a hand crafted vector3 which does not use uBLAS. The only negative impact is that the vector3 always store a "size" member which in this case is redundant [or isn't it? I mean......]. I see it uses the same algorithm, assuming a variable size, but if an operation were to actually change its size, shouldn't it be stopped (assertion)? ublas::bounded_vector<float,3> v3; ublas::bounded_vector<float,2> v2; v3 = v2; std::cout << v3.size() << '\n'; // prints 2 Oh, come on, isn't this just plain betrayal?

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• this program runs but not correctly numbers arent right, i read numbers from a file and then when i

  - by user320950

  this is what i have to do: write a program that determines the grade dispersal for 100 students You are to read the exam scores into three arrays, one array for each exam. You must then calculate how many students scored A’s (90 or above), B’s (80 or above), C’s (70 or above), D’s (60 or above), and F’s (less than 60). Do this for each exam and write the distribution to the screen. // basic file operations #include <iostream> #include <fstream> using namespace std; int read_file_in_array(double exam[100][3]); double calculate_total(double exam1[], double exam2[], double exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); double exam[100][3]; int main() { double go,go2,go3; double exam[100][3],exam1[100],exam2[100],exam3[100]; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; } /* int display_totals() { int grade_total; grade_total=calculate_total(exam1,exam2,exam3); return 0; } */ double calculate_total(double exam1[],double exam2[],double exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0; double exam[100][3]; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { for (j=0; j<3; j++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam[i][j] <=90 && exam[i][j] >=100) { above90++; { if(exam[i][j] <=80 && exam[i][j] >=89) { above80++; { if(exam[i][j] <=70 && exam[i][j] >=79) { above70++; { if(exam[i][j] <=60 && exam[i][j] >=69) { above60++; { if(exam[i][j] >=59) { fail++; } } } } } } } } } } } return 0; } int read_file_in_array(double exam[100][3]) { ifstream infile; int exam1[100]; int exam2[100]; int exam3[100]; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } int num, i=0,j=0; while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; { if (! (infile >> exam[i][j]) ) cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); } return 0; }

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• android Xml-List view with filter

  - by harisali

  Hi, android is new for me. I am trying to develop a program on 1.5 platform but still in progress, plz guide me. I have some information in following format "item1","description1" "item2","description2" "item3","description3" "item4","description4" . . . . I want to show them on screen, I dont know which is recommended way to do this. After google I found 2 method. but I failed to successfully implement any of one. Method 1 I break both columns data into 2 different arrays, then populate listactivity with array of column 1, enable filter & on clicked event I want to raise alert which should show Text clicked in tilte & desc from 2nd array as msg body based on position. But here is problem if using filter index becomes reinitialize :-(, and there didnot find another way to get text of that row. public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setContentView(R.layout.main); setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, Names)); getListView().setTextFilterEnabled(true); } public void onListItemClick(ListView parent, View v, int position, long id) { Builder builder = new AlertDialog.Builder(this); builder.setTitle(Names[position]); builder.setMessage(description[position] + " -> " + position ); builder.setPositiveButton("ok", null); builder.show(); } <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> </LinearLayout> its not picking right item from position if filter used :-(, plz guide Can you share source code of this Method B Here I tried to generate list row from XML , but giving error that 1.5 jar file didnot allow modification :-( public View getView(int position, View convertView, ViewGroup parent) { /* ViewInflate inflater=context.getViewInflate(); View row=inflater.inflate(R.layout.row, null, null); */ View row = (View) convertView; if (row==null) { LayoutInflater inflater=context.getLayoutInflater(); // LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE); row = inflater.inflate(R.layout.row,null); } TextView label=(TextView)row.findViewById(R.id.label); label.setText(items[position]); TextView description=(TextView)row.findViewById(R.id.description); description.setText(items[position]); // ImageView icon=(ImageView)row.findViewById(R.id.icon); // icon.setImageResource(R.drawable.delete); return(row); } Plz suggest what is a right way to acconplish this, so app can show desc of item , has filter too. Plz share If you have any shouce code for this

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• java - unwanted object overwriting

  - by gosling

  Hello everyone! I'm trying to make a program that solves the logic wheels puzzle. I construct the root node and I try to produce the different child-nodes that are produced by making different moves of the wheels. The problem is that while I try to produce the children, the root node is overwrited,and everything is messed-up and I really don't know why. Here you can find the puzzle logic wheels. I represent the wheels as 3x3 arrays. Here is the code that implements the moves: public Node turn_right(Node aNode, int which_wheel) { Node newNode = new Node(aNode.getYellow_wheel(),aNode.getBlue_wheel(),aNode.getGreen_wheel()); int[][] yellow = new int[3][3]; int[][] blue = new int[3][3]; int[][] green = new int[3][3]; if(which_wheel==0) //turn yellow wheel of this node to right { yellow[1][0] = newNode.getYellow_wheel()[0][0]; yellow[2][0] = newNode.getYellow_wheel()[1][0]; yellow[2][1] = newNode.getYellow_wheel()[2][0]; yellow[2][2] = newNode.getYellow_wheel()[2][1]; yellow[1][2] = newNode.getYellow_wheel()[2][2]; yellow[0][2] = newNode.getYellow_wheel()[1][2]; yellow[0][1] = newNode.getYellow_wheel()[0][2]; yellow[0][0] = newNode.getYellow_wheel()[0][1]; blue = newNode.getBlue_wheel(); blue[1][0] = newNode.getYellow_wheel()[1][2]; blue[2][0] = newNode.getYellow_wheel()[2][2]; green = newNode.getGreen_wheel(); } else if(which_wheel == 1)// turn blue wheel of this node to right { blue[1][0] = newNode.getBlue_wheel()[0][0]; blue[2][0] = newNode.getBlue_wheel()[1][0]; blue[2][1] = newNode.getBlue_wheel()[2][0]; blue[2][2] = newNode.getBlue_wheel()[2][1]; blue[1][2] = newNode.getBlue_wheel()[2][2]; blue[0][2] = newNode.getBlue_wheel()[1][2]; blue[0][1] = newNode.getBlue_wheel()[0][2]; blue[0][0] = newNode.getBlue_wheel()[0][1]; yellow = newNode.getYellow_wheel(); yellow[0][2] = newNode.getBlue_wheel()[0][0]; yellow[1][2] = newNode.getBlue_wheel()[1][0]; green = newNode.getGreen_wheel(); green[1][0] = newNode.getBlue_wheel()[1][2]; green[2][0] = newNode.getBlue_wheel()[2][2]; } else if (which_wheel == 2)//turn green wheel of this node to right { green[0][0] = newNode.getGreen_wheel()[0][1]; green[0][1] = newNode.getGreen_wheel()[0][2]; green[0][2] = newNode.getGreen_wheel()[1][2]; green[1][2] = newNode.getGreen_wheel()[2][2]; green[2][2] = newNode.getGreen_wheel()[2][1]; green[2][1] = newNode.getGreen_wheel()[2][0]; green[2][0] = newNode.getGreen_wheel()[1][0]; green[1][0] = newNode.getGreen_wheel()[0][0]; yellow = newNode.getYellow_wheel(); blue = newNode.getBlue_wheel(); blue[0][2] = newNode.getGreen_wheel()[0][0]; blue[1][2] = newNode.getGreen_wheel()[1][0]; } newNode= new Node(yellow,blue,green); return newNode; } There is another function, like this one that does the oposite:it turns the wheels to left. My problem is that I do not want object's aNode tables to be overwritten. Thank you very much.

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• Why does this Quicksort work?

  - by IVlad

  I find this Quicksort partitioning approach confusing and wrong, yet it seems to work. I am referring to this pseudocode. Note: they also have a C implementation at the end of the article, but it's very different from their pseudocode, so I don't care about that. I have also written it in C like this, trying to stay true to the pseudocode as much as possible, even if that means doing some weird C stuff: #include <stdio.h> int partition(int a[], int p, int r) { int x = a[p]; int i = p - 1; int j = r + 1; while (1) { do j = j - 1; while (!(a[j] <= x)); do i = i + 1; while (!(a[i] >= x)); if (i < j) { int t = a[i]; a[i] = a[j]; a[j] = t; } else { for (i = 1; i <= a[0]; ++i) printf("%d ", a[i]); printf("- %d\n", j); return j; } } } int main() { int a[100] = //{8, 6,10,13,15,8,3,2,12}; {7, 7, 6, 2, 3, 8, 4, 1}; partition(a, 1, a[0]); return 0; } If you run this, you'll get the following output: 1 6 2 3 4 8 7 - 5 However, this is wrong, isn't it? Clearly a[5] does not have all the values before it lower than it, since a[2] = 6 > a[5] = 4. Not to mention that 7 is supposed to be the pivot (the initial a[p]) and yet its position is both incorrect and lost. The following partition algorithm is taken from wikipedia: int partition2(int a[], int p, int r) { int x = a[r]; int store = p; for (int i = p; i < r; ++i) { if (a[i] <= x) { int t = a[i]; a[i] = a[store]; a[store] = t; ++store; } } int t = a[r]; a[r] = a[store]; a[store] = t; for (int i = 1; i <= a[0]; ++i) printf("%d ", a[i]); printf("- %d\n", store); return store; } And produces this output: 1 6 2 3 8 4 7 - 1 Which is a correct result in my opinion: the pivot (a[r] = a[7]) has reached its final position. However, if I use the initial partitioning function in the following algorithm: void Quicksort(int a[], int p, int r) { if (p < r) { int q = partition(a, p, r); // initial partitioning function Quicksort(a, p, q); Quicksort(a, q + 1, r); // I'm pretty sure q + r was a typo, it doesn't work with q + r. } } ... it seems to be a correct sorting algorithm. I tested it out on a lot of random inputs, including all 0-1 arrays of length 20. I have also tried using this partition function for a selection algorithm, in which it failed to produce correct results. It seems to work and it's even very fast as part of the quicksort algorithm however. So my questions are: Can anyone post an example on which the algorithm DOESN'T work? If not, why does it work, since the partitioning part seems to be wrong? Is this another partitioning approach that I don't know about?

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• Array not showing in Jlist but filled in console

  - by OVERTONE

  Hey there. been a busy debugger today. ill give ths short version. ive made an array list that takes names from a database. then i put the contents of the arraylist into an array of strings. now i want too display the arrays contents in a JList. the weird thing is it was working earlier. and ive two methods. ones just a little practice too make sure i was adding to the Jlist correctly. so heres the key codes. this is the layout of my code. variables constructor methods in my variables i have these 3 defined String[] contactListNames = new String[5]; ArrayList<String> rowNames = new ArrayList<String>(); JList contactList = new JList(contactListNames); simple enough. in my constructor i have them again. contactListNames = new String[5]; contactList = new JList(contactListNames); //i dont have the array list defined though. printSqlDetails(); // the prinSqldetails was too make sure that the connectionw as alright. and its working fine. fillContactList(); // this is the one thats causing me grief. its where all the work happens. // fillContactListTest(); // this was the tester that makes sure its adding to the list alright. heres the code for fillContactListTest() public void fillContactListTest() { for(int i = 0;i<3;i++) { try { String contact; System.out.println(" please fill the list at index "+ i); Scanner in = new Scanner(System.in); contact = in.next(); contactListNames[i] = contact; in.nextLine(); } catch(Exception e) { e.printStackTrace(); } } } heres the main one thats supposed too work. public void fillContactList() { int i =0; createConnection(); ArrayList<String> rowNames = new ArrayList<String>(); try { Statement stmt = conn.createStatement(); ResultSet namesList = stmt.executeQuery("SELECT name FROM Users"); try { while (namesList.next()) { rowNames.add(namesList.getString(1)); contactListNames =(String[])rowNames.toArray(new String[rowNames.size()]); // this used to print out contents of array list // System.out.println("" + rowNames); while(i<contactListNames.length) { System.out.println(" " + contactListNames[i]); i++; } } } catch(SQLException q) { q.printStackTrace(); } conn.commit(); stmt.close(); conn.close(); } catch(SQLException e) { e.printStackTrace(); } } i really need help here. im at my wits end. i just cant see why the first method would add to the JList no problem. but the second one wont. both the contactListNames array and array list can print fine and have the names in them. but i must be transfering them too the jlist wrong. please help p.s im aware this is long. but trust me its the short version.

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• ZF: Form array field - how to display values in the view correctly

  - by Wojciech Fracz

  Let's say I have a Zend_Form form that has a few text fields, e.g: $form = new Zend_Form(); $form->addElement('text', 'name', array( 'required' => true, 'isArray' => true, 'filters' => array( /* ... */ ), 'validators' => array( /* ... */ ), )); $form->addElement('text', 'surname', array( 'required' => true, 'isArray' => true, 'filters' => array( /* ... */ ), 'validators' => array( /* ... */ ), )); After rendering it I have following HTML markup (simplified): <div id="people"> <div class="person"> <input type="text" name="name[]" /> <input type="text" name="surname[]" /> </div> </div> Now I want to have the ability to add as many people as I want. I create a "+" button that in Javascript appends next div.person to the container. Before I submit the form, I have for example 5 names and 5 surnames, posted to the server as arrays. Everything is fine unless somebody puts the value in the field that does not validate. Then the whole form validation fails and when I want to display the form again (with errors) I see the PHP Warning: htmlspecialchars() expects parameter 1 to be string, array given Which is more or less described in ticket: http://framework.zend.com/issues/browse/ZF-8112 However, I came up with a not-very-elegant solution. What I wanted to achieve: have all fields and values rendered again in the view have error messages only next to the fields that contained bad values Here is my solution (view script): <div id="people"> <?php $names = $form->name->getValue(); // will have an array here if the form were submitted $surnames= $form->surname->getValue(); // only if the form were submitted we need to validate fields' values // and display errors next to them; otherwise when user enter the page // and render the form for the first time - he would see Required validator // errors $needsValidation = is_array($names) || is_array($surnames); // print empty fields when the form is displayed the first time if(!is_array($names))$names= array(''); if(!is_array($surnames))$surnames= array(''); // display all fields! foreach($names as $index => $name): $surname = $surnames[$index]; // validate value if needed if($needsValidation){ $form->name->isValid($name); $form->surname->isValid($surname); } ?> <div class="person"> <?=$form->name->setValue($name); // display field with error if did not pass the validation ?> <?=$form->surname->setValue($surname);?> </div> <?php endforeach; ?> </div> The code work, but I want to know if there is an appropriate, more comfortable way to do this? I often hit this problem when there is a need for a more dynamic - multivalue forms and have not find better solution for a long time.

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• (Ordered) Set Partitions in fixed-size Blocks

  - by Eugen

  Here is a function I would like to write but am unable to do so. Even if you don't / can't give a solution I would be grateful for tips. For example, I know that there is a correlation between the ordered represantions of the sum of an integer and ordered set partitions but that alone does not help me in finding the solution. So here is the description of the function I need: The Task Create an efficient* function List<int[]> createOrderedPartitions(int n_1, int n_2,..., int n_k) that returns a list of arrays of all set partions of the set {0,...,n_1+n_2+...+n_k-1} in number of arguments blocks of size (in this order) n_1,n_2,...,n_k (e.g. n_1=2, n_2=1, n_3=1 -> ({0,1},{3},{2}),...). Here is a usage example: int[] partition = createOrderedPartitions(2,1,1).get(0); partition[0]; // -> 0 partition[1]; // -> 1 partition[2]; // -> 3 partition[3]; // -> 2 Note that the number of elements in the list is (n_1+n_2+...+n_n choose n_1) * (n_2+n_3+...+n_n choose n_2) * ... * (n_k choose n_k). Also, createOrderedPartitions(1,1,1) would create the permutations of {0,1,2} and thus there would be 3! = 6 elements in the list. * by efficient I mean that you should not initially create a bigger list like all partitions and then filter out results. You should do it directly. Extra Requirements If an argument is 0 treat it as if it was not there, e.g. createOrderedPartitions(2,0,1,1) should yield the same result as createOrderedPartitions(2,1,1). But at least one argument must not be 0. Of course all arguments must be = 0. Remarks The provided pseudo code is quasi Java but the language of the solution doesn't matter. In fact, as long as the solution is fairly general and can be reproduced in other languages it is ideal. Actually, even better would be a return type of List<Tuple<Set>> (e.g. when creating such a function in Python). However, then the arguments wich have a value of 0 must not be ignored. createOrderedPartitions(2,0,2) would then create [({0,1},{},{2,3}),({0,2},{},{1,3}),({0,3},{},{1,2}),({1,2},{},{0,3}),...] Background I need this function to make my mastermind-variation bot more efficient and most of all the code more "beautiful". Take a look at the filterCandidates function in my source code. There are unnecessary / duplicate queries because I'm simply using permutations instead of specifically ordered partitions. Also, I'm just interested in how to write this function. My ideas for (ugly) "solutions" Create the powerset of {0,...,n_1+...+n_k}, filter out the subsets of size n_1, n_2 etc. and create the cartesian product of the n subsets. However this won't actually work because there would be duplicates, e.g. ({1,2},{1})... First choose n_1 of x = {0,...,n_1+n_2+...+n_n-1} and put them in the first set. Then choose n_2 of x without the n_1 chosen elements beforehand and so on. You then get for example ({0,2},{},{1,3},{4}). Of course, every possible combination must be created so ({0,4},{},{1,3},{2}), too, and so on. Seems rather hard to implement but might be possible. Research I guess this goes in the direction I want however I don't see how I can utilize it for my specific scenario. http://rosettacode.org/wiki/Combinations

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• iPhone game and reading plist file and looping through multidimensional array.

  - by Fulvio

  I have a question regarding an iPhone game I'm developing. At the moment, below is the code I'm using to currently I loop through my multidimensional array and position bricks accordingly on my scene. Instead of having multiple two dimensional arrays within my code as per the following (gameLevel1). Ideally, I'd like to read from a .plist file within my project and loop through the values in that instead. Please take into account that I'd like to have more than one level within my game (possibly 20) so my .plist file would have to have some sort of separator line item to determine what level I want to render. I was then thinking of having some sort of method that I call and that method would take the level number I'm interested in rendering. e.g. Method? +(void)renderLevel:(NSString levelNumber); e.g. .plist file? #LEVEL_ONE# 0,0,0,0,0,0,0,0,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,0,0,0,0,0,0,0,0 #LEVEL_TWO# 1,0,0,0,0,0,0,0,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,0,0,0,0,0,0,0,1 Code that I'm currently using: int gameLevel[17][9] = { { 0,0,0,0,0,0,0,0,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,0,0,0,0,0,0,0,0 } }; for (int row=0; row < 17; row++) { for (int col=0; col < 17; col++) { thisBrickValue = gameLevel[row][col]; xOffset = 35 * floor(col); yOffset = 22 * floor(row); switch (thisBrickValue) { case 0: brick = [[CCSprite spriteWithFile:@"block1.png"] autorelease]; break; case 1: brick = [[CCSprite spriteWithFile:@"block0.png"] autorelease]; break; } brick.position = ccp(xOffset, yOffset); [self addChild:brick]; } }

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• ActionScript Gradient Banding Problem

  - by TheDarkIn1978

  i'm having a strange issue with banding between certain colors of a gradient. to create the gradient, i'm drawing evenly spaced circle wedges from the center to the border, and filling each circle wedge from a bitmap line gradient pixel in a loop. public class ColorWheel extends Sprite { private static const DEFAULT_RADIUS:Number = 100; private static const DEFAULT_BANDING_QUALITY:int = 3600; public function ColorWheel(nRadius:Number = DEFAULT_RADIUS) { init(nRadius); } public function init(nRadius:Number = DEFAULT_RADIUS):void { var nRadians : Number; var nColor : Number; var objMatrix : Matrix = new Matrix(); var nX : Number; var nY : Number; var previousX : Number = nRadius; var previousY : Number = 0; var leftToRightColors:Array = new Array(0xFF0000, 0xFFFF00, 0x00FF00, 0x00FFFF, 0x0000FF, 0xFF00FF); leftToRightColors.push(leftToRightColors[0]); var leftToRightAlphas:Array = new Array(); var leftToRightRatios:Array = new Array(); var leftToRightPartition:Number = 255 / (leftToRightColors.length - 1); //Push arrays for (var j:int = 0; j < leftToRightColors.length; j++) { leftToRightAlphas.push(1); leftToRightRatios.push(j * leftToRightPartition); } var leftToRightColorsMatrix:Matrix = new Matrix(); leftToRightColorsMatrix.createGradientBox(DEFAULT_BANDING_QUALITY, 1); //Produce a horizontal leftToRightLine sprite var leftToRightLine:Sprite = new Sprite(); leftToRightLine.graphics.lineStyle(1, 0, 1, false, LineScaleMode.NONE, CapsStyle.NONE); leftToRightLine.graphics.lineGradientStyle(GradientType.LINEAR, leftToRightColors, leftToRightAlphas, leftToRightRatios, leftToRightColorsMatrix); leftToRightLine.graphics.moveTo(0, 0); leftToRightLine.graphics.lineTo(DEFAULT_BANDING_QUALITY, 0); //Assign bitmapData to the leftToRightLine var leftToRightLineBitmapData:BitmapData = new BitmapData(leftToRightLine.width, leftToRightLine.height); leftToRightLineBitmapData.draw(leftToRightLine); for(var i:int = 1; i < (DEFAULT_BANDING_QUALITY + 1); i++) { // Convert the degree to radians. nRadians = i * (Math.PI / (DEFAULT_BANDING_QUALITY / 2)); // OR the individual color channels together. nColor = leftToRightLineBitmapData.getPixel(i-1, 0); // Calculate the coordinate in which the line should be drawn to. nX = nRadius * Math.cos(nRadians); nY = nRadius * Math.sin(nRadians); // Create a matrix for the wedges gradient color. objMatrix.createGradientBox(nRadius * 2, nRadius * 2, nRadians, -nRadius, -nRadius); graphics.beginGradientFill(GradientType.LINEAR, [nColor, nColor], [1, 1], [127, 255], objMatrix); graphics.moveTo( 0, 0 ); graphics.lineTo( previousX, previousY ); graphics.lineTo( nX, nY ); graphics.lineTo( 0, 0 ); graphics.endFill(); previousX = nX; previousY = nY; } } } i'm creating a circle with 3600 wedges, although it doesn't look like it based on the screen shot within the orange color that is produced from gradating from red to yellow numbers. adding a orange number between red and yellow doesn't help. but if i create the circle with only 360 wedges, the gradient banding is much more obvious. 3600 is probably overkill, and doesn't really add more detail over, say, making the circle of 1440 wedges, but i don't know any other way to slightly elevate this banding issue. any ideas how i can fix this, or what i'm doing wrong? could it be caused by the circleMatrix rotation?

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• Retrieving multiple rows from a loop-created form... Stuck.

  - by hangston

  Let me start by saying that I'm new to PHP, but I'm here to learn and would really appreciate your help. I use the following code to pull in data and create a form. This creates up to 40 lines for a user to fill out. Each line consists of the same information: Description, Amount, and Frequency. The remainder of the information needed is generated by the database. (See hidden fields) <?php $row = 0; do { $optid = $row_options['option_id']; echo "<tr>\n\t<td>" . htmlentities($row_options['option']) . "</td>\n"; echo "\t<td>" . "<input name='description' type='text' size='40' maxlength='120'/>" . "</td>\n"; echo "\t<td>" . "<input name='option_id' type='hidden' value='$optid' />$<input name='amount' type='text' size='10' maxlength='7'/>" . "</td>\n"; echo "\t<td>" . "<select name='assisted_frequency'> <option value='Monthly'>Monthly</option> <option value='Weekly'>Weekly</option> <option value='Daily'>Daily</option> <option value='Hourly'>Hourly</option> <option value='One-Time'>One-Time</option> </select>" . "</td>\n</tr>\n"; $array[$row] = array( $arraydesc[$row] = $_POST['description'], $arrayamto[$row] = $_POST['amount'], $arrayoptid[$row] = $optid, $arrayfreq[$row] = $_POST['frequency'], ); $row ++; } while ($row_options = mysql_fetch_assoc($options)); $counter = $row - 1; ?> I'm having troubles retrieving the information that the user inputs. My intent is to loop through each row after the user has input their information, then upload the mix of my database information and the user's information into another database. For example, the user would see, albeit prettier: form1 Option 1: description [input box] amount [input box] frequency [option box] Option 2: description [input box] amount [input box] frequency [option box] Option 3: description [input box] amount [input box] frequency [option box] Option 4: description [input box] amount [input box] frequency [option box] submit Upon submitting the form above, I'm using a query similar to the following to input the data into the database: for($row=0; $row<=$counter; $row++){ $insertSQL2 = sprintf("INSERT INTO table (option_id, amount, description, frequency) VALUES (%s, %s, %s, %s)", GetSQLValueString($arrayoptid[$row], "int"), GetSQLValueString($arrayamto[$row], "int"), GetSQLValueString($arraydesc[$row], "text"), GetSQLValueString($arrayfreq[$row], "text")); // code to submit query } I've tried for, foreach, arrays (what feels like the everything I know) to post each row (row by row) into the database. I either get just the last row of data, or no data at all. I also worry that the [$row] technique is adding characters to my data. What is the best way to retrieve each row of the user's inputs, then upload this data (row by row) into the database? Also, I would really appreciate your suggestions for improving my coding technique and the approach I'm taking.

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• Having trouble storing a CRTP based class in a vector

  - by user366834

  Hi, Im not sure if this can be done, im just delving into templates so perhaps my understanding is a bit wrong. I have a Platoon of soldiers, the platoon inherits from a formation to pick up the formations properties, but because i could have as many formations as i can think of I chose to use the CRTP to create the formations, hoping that i could make a vector or array of Platoon to store the platoons in. but, of course, when i make a Platoon, it wont store it in the vector, "types are unrelated" Is there any way around this ? i read about "Veneers" which are similar and that they work with arrays but i cant get it to work, perhaps im missing something. here's some code: (sorry about the formatting, the code is here in my post but its not showing up for some reason ) template < class TBase > class IFormation { public : ~IFormation(){} bool IsFull() { return m_uiMaxMembers == m_uiCurrentMemCount; } protected: unsigned int m_uiCurrentMemCount; unsigned int m_uiMaxMembers; IFormation( unsigned int _uiMaxMembers ): m_uiMaxMembers( _uiMaxMembers ), m_uiCurrentMemCount( 0 ){} // only allow use as a base class. void SetupFormation( std::vector<MySoldier*>& _soldierList ){}; // must be implemented in derived class }; ///////////////////////////////////////////////////////////////////////////////// // PHALANX FORMATION class Phalanx : public IFormation<Phalanx> { public: Phalanx( ): IFormation( 12 ), m_fDistance( 4.0f ) {} ~Phalanx(){} protected: float m_fDistance; // the distance between soldiers void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; /////////////////////////////////////////////////////////////////////////////////// // COLUMN FORMATINO class Column : public IFormation< Column > { public : Column( int _numOfMembers ): IFormation( _numOfMembers ) {} ~Column(); protected: void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; I then use these formations in the platoon class to derive, so that platoon gets the relevant SetupFormation() function: template < class Formation > class Platoon : public Formation { public: **** platoon code here }; everything works great and as expected up until this point. now, as my general can have multiple platoons, I need to store the platoons. typedef Platoon< IFormation<> > TPlatoon; // FAIL typedef std::vector<TPlatoon*> TPlatoons; TPlatoon m_pPlatoons m_pPlatoons.push_back( new Platoon<Phalanx> ); // FAIL, types unrelated. typedef Platoon< IFormation< TPlatoon; fails because i need to specify a template parameter, yet specifying this will only allow me to store platoons created with the same template parameter. so i then created FormationBase class FormationBase { public: virtual bool IsFull() = 0; virtual void SetupFormation( std::vector<MySoldier*>& _soldierList ) = 0; }; and made IFormation publicly inherit from that, and then changed the typedef to typedef Platoon< IFormation< FormationBase > > TPlatoon; but still no love. now in my searches i have not found info that says this is possible - or not possible.

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• Reusing my PagedList object on WCF

  - by AlexCode

  The problem: I have a custom collection PagedList<T> that is being returned from my WCF service as PagedListOfEntitySearchResultW_SH0Zpu5 when T is EntitySearchResult object. I want to reuse this PagedList<T> type between the application and the service. My scenario: I've created a PagedList<T> type that inherits from List<T>. This type is on a separated assembly that is referenced on both application and WCF service. I'm using the /reference option on the scvutil to enable the type reusing. I also don't want any arrays returned so I also use the /collection to map to the generic List type. I'm using the following svcutil command to generate the service proxy: "C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\NETFX 4.0 Tools\svcutil.exe" /collectionType:System.Collections.Generic.List`1 /reference:..\..\bin\Debug\App.Utilities.dll http://localhost/App.MyService/MyService.svc?wsdl /namespace:*,"App.ServiceReferences.MyService" /out:..\ServiceProxy\MyService.cs The PagedList object is something like: [CollectionDataContract] public partial class PagedList<T> : List<T> { public PagedList() { } /// <summary> /// Creates a new instance of the PagedList object and doesn't apply any pagination algorithm. /// The only calculated property is the TotalPages, everything else needed must be passed to the object. /// </summary> /// <param name="source"></param> /// <param name="pageNumber"></param> /// <param name="pageSize"></param> /// <param name="totalRecords"></param> public PagedList(IEnumerable<T> source, int pageNumber, int pageSize, int totalRecords) { if (source == null) source = new List<T>(); this.AddRange(source); PagingInfo.PageNumber = pageNumber; PageSize = pageSize; TotalRecords = totalRecords; } public PagedList(IEnumerable<T> source, PagingInfo paging) { this.AddRange(source); this._pagingInfo = paging; } [DataMember] public int TotalRecords { get; set; } [DataMember] public int PageSize { get; set; } public int TotalPages() { if (this.TotalRecords > 0 && PageSize > 0) return (int)Math.Ceiling((double)TotalRecords / (double)PageSize); else return 0; } public bool? HasPreviousPage() { return (PagingInfo.PageNumber > 1); } public bool? HasNextPage() { return (PagingInfo.PageNumber < TotalPages()); } public bool? IsFirstPage() { return PagingInfo.PageNumber == 1; } public bool? IsLastPage() { return PagingInfo.PageNumber == TotalPages(); } PagingInfo _pagingInfo = null; [DataMember] public PagingInfo PagingInfo { get { if (_pagingInfo == null) _pagingInfo = new PagingInfo(); return _pagingInfo; } set { _pagingInfo = value; } } }

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• Retreiving multiple rows from a loop-created form... Stuck.

  - by hangston

  Hi All, Let me start by saying that I'm new to PHP, but I'm here to learn and would really appreciate your help. I use the following code to pull in data and create a form. This creates up to 40 lines for a user to fill out. Each line consists of the same information: Description, Amount, and Frequency. The remainder of the information needed is generated by the database. (See hidden fields) <?php $row = 0; do { $optid = $row_options['option_id']; echo "<tr>\n\t<td>" . htmlentities($row_options['option']) . "</td>\n"; echo "\t<td>" . "<input name='description' type='text' size='40' maxlength='120'/>" . "</td>\n"; echo "\t<td>" . "<input name='option_id' type='hidden' value='$optid' />$<input name='amount' type='text' size='10' maxlength='7'/>" . "</td>\n"; echo "\t<td>" . "<select name='assisted_frequency'> <option value='Monthly'>Monthly</option> <option value='Weekly'>Weekly</option> <option value='Daily'>Daily</option> <option value='Hourly'>Hourly</option> <option value='One-Time'>One-Time</option> </select>" . "</td>\n</tr>\n"; $array[$row] = array( $arraydesc[$row] = $_POST['description'], $arrayamto[$row] = $_POST['amount'], $arrayoptid[$row] = $optid, $arrayfreq[$row] = $_POST['frequency'], ); $row ++; } while ($row_options = mysql_fetch_assoc($options)); $counter = $row - 1; ?> I'm having troubles retrieving the information that the user inputs. My intent is to loop through each row after the user has input their information, then upload the mix of my database information and the user's information into another database. For example, the user would see, albeit prettier: form1 Option 1: description [input box] amount [input box] frequency [option box] Option 2: description [input box] amount [input box] frequency [option box] Option 3: description [input box] amount [input box] frequency [option box] Option 4: description [input box] amount [input box] frequency [option box] submit Upon submitting the form above, I'm using a query similar to the following to input the data into the database: for($row=0; $row<=$counter; $row++){ $insertSQL2 = sprintf("INSERT INTO table (option_id, amount, description, frequency) VALUES (%s, %s, %s, %s)", GetSQLValueString($arrayoptid[$row], "int"), GetSQLValueString($arrayamto[$row], "int"), GetSQLValueString($arraydesc[$row], "text"), GetSQLValueString($arrayfreq[$row], "text")); // code to submit query } I've tried for, foreach, arrays (what feels like the everything I know) to post each row (row by row) into the database. I either get just the last row of data, or no data at all. I also worry that the [$row] technique is adding characters to my data. What is the best way to retrieve each row of the user's inputs, then upload this data (row by row) into the database? Also, I would really appreciate your suggestions for improving my coding technique and the approach I'm taking. Thank you, Hangston

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• Perl kill(0, $pid) in Windows always returning 1

  - by banshee_walk_sly

  I'm trying to make a Perl script that will run a set of other programs in Windows. I need to be able to capture the stdout, stderr, and exit code of the process, and I need to be able to see if a process exceeds it's allotted execution time. Right now, the pertinent part of my code looks like: ... $pid = open3($wtr, $stdout, $stderr, $command); if($time < 0){ waitpid($pid, 0); $return = $? >> 8; $death_sig = $? & 127; $core_dump = $? & 128; } else{ # Do timeout stuff, currently not working as planned print "pid: $pid\n"; my $elapsed = 0; #THIS LOOP ONLY TERMINATES WHEN $time > $elapsed ...? while(kill 0, $pid and $time > $elapsed){ Time::HiRes::usleep(1000); # sleep for milliseconds $elapsed += 1; $return = $? >> 8; $death_sig = $? & 127; $core_dump = $? & 128; } if($elapsed >= $time){ $status = "FAIL"; print $log "TIME LIMIT EXCEEDED\n"; } } #these lines are needed to grab the stdout and stderr in arrays so # I may reuse them in multiple logs if(fileno $stdout){ @stdout = <$stdout>; } if(fileno $stderr){ @stderr = <$stderr>; } ... Everything is working correctly if $time = -1 (no timeout is needed), but the system thinks that kill 0, $pid is always 1. This makes my loop run for the entirety of the time allowed. Some extra details just for clarity: This is being run on Windows. I know my process does terminate because I have get all the expected output. Perl version: This is perl, v5.10.1 built for MSWin32-x86-multi-thread (with 2 registered patches, see perl -V for more detail) Copyright 1987-2009, Larry Wall Binary build 1007 [291969] provided by ActiveState http://www.ActiveState.com Built Jan 26 2010 23:15:11 I appreciate your help :D For that future person who may have a similar issue I got the code to work, here is the modified code sections: $pid = open3($wtr, $stdout, $stderr, $command); close($wtr); if($time < 0){ waitpid($pid, 0); } else{ print "pid: $pid\n"; my $elapsed = 0; while(waitpid($pid, WNOHANG) <= 0 and $time > $elapsed){ Time::HiRes::usleep(1000); # sleep for milliseconds $elapsed += 1; } if($elapsed >= $time){ $status = "FAIL"; print $log "TIME LIMIT EXCEEDED\n"; } } $return = $? >> 8; $death_sig = $? & 127; $core_dump = $? & 128; if(fileno $stdout){ @stdout = <$stdout>; } if(fileno $stderr){ @stderr = <$stderr>; } close($stdout); close($stderr);

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• Sending XML to Servlet from Action Script

  - by John Doe

  I am only getting empty arrays on output. Anyone know what Exactly I'm doing wrong? package myDungeonAccessor; /* * To change this template, choose Tools | Templates * and open the template in the editor. */ import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class myDungeonAccessorServlet extends HttpServlet { private myDungeonAccessor dataAccessor; /** * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods. * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* TODO output your page here out.println("<html>"); out.println("<head>"); out.println("<title>Servlet myDungeonAccessorServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Servlet myDungeonAccessorServlet at " + request.getContextPath () + "</h1>"); out.println("</body>"); out.println("</html>"); */ } finally { out.close(); } } // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> /** * Handles the HTTP <code>GET</code> method. * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); // PrintWriter out = response.getWriter(); System.out.println("yo mom"); } /** * Handles the HTTP <code>POST</code> method. * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //System.out.println("heppo"); //dataAccessor = new myDungeonAccessor(); System.out.println("Hello"); try { System.out.println("HEADERS: " + request.getHeaderNames()); ObjectInputStream in = new ObjectInputStream(request.getInputStream()); ObjectOutputStream out = new ObjectOutputStream(response.getOutputStream()); } catch(Exception e) { e.printStackTrace(); } System.out.println("WAZZUP"); byte [] buffer = new byte[4096]; //in.read(buffer); System.out.println("TEST!"); String s = new String(buffer); System.out.println("Update S:" + s); } /** * Returns a short description of the servlet. * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } }

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• First time using select(), maybe a basic question?

  - by darkletter

  Hello people, i've been working for a few days with this server using select(). What it does, is that, i have two arrays of clients (one is "suppliers", and the other is "consumers"), and the mission of the server is to check whether the suppliers have something to send to the consumers, and in case affirmative, send it. The second part of the server is that, when the consumers have received the suppliers' info, they send a confirmation message to the same suppliers that sent the info. When a client connects, it gets recognized as "undefined", until it sends a message with the word "supplier" or "consumer" (in Spanish, as i'm from there), when the server puts it in the correct clients array. Well, what the server does is not very important here. What's important is that, i'm doing both parts with two different "for" loops, and that's where i'm getting the problems. When the first user connects to the server (be it a supplier or a consumer), the server gets stuck in the first or second loop, instead of just continuing its execution. As it's the first time i'm using select(), i may be missing something. Could you guys give me any sort of help? Thanks a lot in advance. for(;;) { rset=allset; nready=select(maxfd+1,&rset,NULL,NULL,NULL); if (FD_ISSET(sockfd, &rset)){ clilen=sizeof(cliente); if((connfd=accept(sockfd,(struct sockaddr *)&cliente,&clilen))<0) printf("Error"); IP=inet_ntoa(cliente.sin_addr); for(i=0;i<COLA;i++){if(indef[i]<0){indef[i]=connfd;IPind[i]=IP;break;}} FD_SET(connfd,&allset); if(connfd > maxfd) maxfd=connfd; if(i>maxii) maxii=i; if(--nready<=0) continue; }// Fin ISSET(sockfd) for(i=0;i<=maxii;i++){ if((sockfd1=indef[i])<0){ continue;} //! if(FD_ISSET(sockfd1,&rset)){ if((n=read(sockfd1,comp,MAXLINE))==0){close(sockfd1);FD_CLR(sockfd1,&allset);indef[i]=-1;printf("Cliente indefinido desconectado \n");} else{ comp[n]='\0'; if(strcmp(comp,"suministrador")==0){ for(j=0;j<=limite;j++){if(sumi[j]<0){IPsum[j]=IPind[i];sumi[j]=indef[i]; indef[i]=-1;if(j>maxis) {maxis=j;}break; } } } else if(strcmp(comp,"consumidor")==0){ for(o=0;j<=limite;j++){if(consum[o]<0){IPcons[o]=IPind[i];consum[o]=indef[i]; indef[o]=-1;if(o>maxic) {maxic=o;}break; } } } if(--nready <=0)break; } } }//fin bucle for maxii for(i=0;i<=maxis;i++){ if((sockfd2=sumi[i])<0){continue;} if(FD_ISSET(sockfd2,&rset)){ if((n=read(sockfd2,buffer2,MAXLINE))==0){close(sockfd2);FD_CLR(sockfd2,&allset);sumi[i]=-1;printf("Suministrador desconectado \n");} else{ buffer2[n]='\0'; for(j=0;j<=maxic;j++){ if((sockfd3=consum[j])<0){ continue;} else {strcpy(final,IPsum[i]);strcat(final,":");strcat(final,buffer2);write(sockfd3,final,sizeof(final));respuesta[i]=1;} } break; // ? } } }//fin for maxis for(i=miniic;i<=maxic;i++){ if((sockfd4=consum[i])<0){continue;} if(FD_ISSET(sockfd4,&rset)){ if((n=read(sockfd4,buffer3,MAXLINE))==0){close(sockfd4);FD_CLR(sockfd4,&allset);consum[i]=-1;printf("Consumidor desconectado \n");} else{ buffer3[n]='\0'; IP2=strtok(buffer3,":"); obj=strtok(NULL,":"); for(j=0;j<100;j++){ if((strcmp(IPsum[j],IP2)==0) && (respuesta[j]==1)) {write(sumi[j],obj,sizeof(obj)); miniic=i+1; respuesta[j]=0; break; } } } } }

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• Find the right value in recursive array

  - by fire

  I have an array with multiple sub-arrays like this: Array ( [0] => Array ( [Page_ID] => 1 [Page_Parent_ID] => 0 [Page_Title] => Overview [Page_URL] => overview [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [0] => Array ( [Page_ID] => 2 [Page_Parent_ID] => 1 [Page_Title] => Team [Page_URL] => overview/team [Page_Type] => content [Page_Order] => 1 ) ) [2] => Array ( [Page_ID] => 3 [Page_Parent_ID] => 0 [Page_Title] => Funds [Page_URL] => funds [Page_Type] => content [Page_Order] => 2 ) [3] => Array ( [0] => Array ( [Page_ID] => 4 [Page_Parent_ID] => 3 [Page_Title] => Strategy [Page_URL] => funds/strategy [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [0] => Array ( [Page_ID] => 7 [Page_Parent_ID] => 4 [Page_Title] => A Class Fund [Page_URL] => funds/strategy/a-class-fund [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [0] => Array ( [Page_ID] => 10 [Page_Parent_ID] => 7 [Page_Title] => Information [Page_URL] => funds/strategy/a-class-fund/information [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [Page_ID] => 11 [Page_Parent_ID] => 7 [Page_Title] => Fund Data [Page_URL] => funds/strategy/a-class-fund/fund-data [Page_Type] => content [Page_Order] => 2 ) ) [2] => Array ( [Page_ID] => 8 [Page_Parent_ID] => 4 [Page_Title] => B Class Fund [Page_URL] => funds/strategy/b-class-fund [Page_Type] => content [Page_Order] => 2 ) I need a function to find the right Page_URL so if you know the $url is "funds/strategy/a-class-fund" I need to pass that to a function that returns a single array result (which would be the Page_ID = 7 array in this example). Having a bit of a stupid day, any help would be appreciated!

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• Effective optimization strategies on modern C++ compilers

  - by user168715

  I'm working on scientific code that is very performance-critical. An initial version of the code has been written and tested, and now, with profiler in hand, it's time to start shaving cycles from the hot spots. It's well-known that some optimizations, e.g. loop unrolling, are handled these days much more effectively by the compiler than by a programmer meddling by hand. Which techniques are still worthwhile? Obviously, I'll run everything I try through a profiler, but if there's conventional wisdom as to what tends to work and what doesn't, it would save me significant time. I know that optimization is very compiler- and architecture- dependent. I'm using Intel's C++ compiler targeting the Core 2 Duo, but I'm also interested in what works well for gcc, or for "any modern compiler." Here are some concrete ideas I'm considering: Is there any benefit to replacing STL containers/algorithms with hand-rolled ones? In particular, my program includes a very large priority queue (currently a std::priority_queue) whose manipulation is taking a lot of total time. Is this something worth looking into, or is the STL implementation already likely the fastest possible? Along similar lines, for std::vectors whose needed sizes are unknown but have a reasonably small upper bound, is it profitable to replace them with statically-allocated arrays? I've found that dynamic memory allocation is often a severe bottleneck, and that eliminating it can lead to significant speedups. As a consequence I'm interesting in the performance tradeoffs of returning large temporary data structures by value vs. returning by pointer vs. passing the result in by reference. Is there a way to reliably determine whether or not the compiler will use RVO for a given method (assuming the caller doesn't need to modify the result, of course)? How cache-aware do compilers tend to be? For example, is it worth looking into reordering nested loops? Given the scientific nature of the program, floating-point numbers are used everywhere. A significant bottleneck in my code used to be conversions from floating point to integers: the compiler would emit code to save the current rounding mode, change it, perform the conversion, then restore the old rounding mode --- even though nothing in the program ever changed the rounding mode! Disabling this behavior significantly sped up my code. Are there any similar floating-point-related gotchas I should be aware of? One consequence of C++ being compiled and linked separately is that the compiler is unable to do what would seem to be very simple optimizations, such as move method calls like strlen() out of the termination conditions of loop. Are there any optimization like this one that I should look out for because they can't be done by the compiler and must be done by hand? On the flip side, are there any techniques I should avoid because they are likely to interfere with the compiler's ability to automatically optimize code? Lastly, to nip certain kinds of answers in the bud: I understand that optimization has a cost in terms of complexity, reliability, and maintainability. For this particular application, increased performance is worth these costs. I understand that the best optimizations are often to improve the high-level algorithms, and this has already been done.

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• not able to show the file from the array...

  - by sjl

  Hi, i'm trying to do an image gallery. i was not able to display the thumbnails stored in the array. instead it keep showing the same thumbnails. anyone can help? very much appreciated.. // Arrays that store the filenames of the text, images and thumbnails var thumbnails:Array = [ "images/image1_thumb.jpg", "images/image2_thumb.jpg", "images/image3_thumb.jpg", "images/image4_thumb.jpg", "images/image5_thumb.jpg", "images/image6_thumb.jpg", "images/image7_thumb.jpg" ]; var images:Array = [ "images/image1.jpg", "images/image2.jpg", "images/image3.jpg", "images/image4.jpg", "images/image5.jpg", "images/image6.jpg", "images/image7.jpg" ]; var textFiles:Array = [ "text/picture1.txt", "text/picture2.txt", "text/picture3.txt", "text/picture4.txt", "text/picture5.txt", "text/picture6.txt", "text/picture7.txt" ]; // NOTE: thumbnail images are 60 x 43 pixels in size // loop through the array and create the thumbnails and position them vertically for (var i:int = 0; i <7; i++) { // create an instance of MyUIThumbnail var thumbs:MyUIThumbnail = new MyUIThumbnail(); // position the thumbnails on the left vertically thumbs.y = 43 * i;/*** FILL IN THE BLANK HERE ***/ // store the corresponding full size image name in the thumbnail // use the "images" array thumbs.image = "images/image1.jpg"; thumbs.image = "images/image2.jpg"; thumbs.image = "images/image3.jpg"; thumbs.image = "images/image4.jpg"; thumbs.image = "images/image5.jpg"; thumbs.image = "images/image6.jpg"; thumbs.image = "images/image7.jpg"; // store the corresponding text file name in the thumbnail // use the "textFiles" array thumbs.textFile = "text/picture1.txt"; thumbs.textFile = "text/picture2.txt"; thumbs.textFile = "text/picture3.txt"; thumbs.textFile = "text/picture4.txt"; thumbs.textFile = "text/picture5.txt"; thumbs.textFile = "text/picture6.txt"; thumbs.textFile = "text/picture7.txt"; thumbs.imageFullSize = full_image_mc ; // store the reference to the textfield in the thumbnail thumbs.infoText = info; // load and display the thumbnails // use the "thumbnails" array thumbs.loadThumbnail("images/image1_thumb.jpg"); thumbs.loadThumbnail("images/image2_thumb.jpg"); thumbs.loadThumbnail("images/image3_thumb.jpg"); thumbs.loadThumbnail("images/image4_thumb.jpg"); thumbs.loadThumbnail("images/image5_thumb.jpg"); thumbs.loadThumbnail("images/image6_thumb.jpg"); thumbs.loadThumbnail("images/image7_thumb.jpg"); addChild(thumbs); } below is my thumbanail. as package{ import fl.containers.; import flash.events.; import flash.text.; import flash.net.; import flash.display.*; public class MyUIThumbnail extends MovieClip { public var image:String = ""; public var textFile:String = ""; var loader:UILoader = new UILoader(); public var imageFullSize:MyFullSizeImage; // reference to loader to show the full size image public var infoText:TextField; // reference to textfield that displays image infoText var txtLoader:URLLoader = new URLLoader(); // loader to load the text file public function MyUIThumbnail() { buttonMode = true; addChild(loader); this.addEventListener(MouseEvent.CLICK, myClick); txtLoader.addEventListener(Event.COMPLETE, displayText); loader.addEventListener(Event.COMPLETE, thumbnailLoaded); } public function loadThumbnail(filename:String):void { loader.source = filename; preloader.trackLoading(loader); } function myClick(e:MouseEvent):void { // load and display the full size image imageFullSize.loadImage("my_full_mc"); // load and display the text textLoad("info"); } function textLoad(file:String) { // load the text description from the text file loader.load(new URLRequest(textFile)); } function displayText(e:Event) { //display the text when loading is completed addChild(infoText); } function thumbnailLoaded(e:Event) { loader.width = 60; loader.height = 43; } } }

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• How can I remove this query from within a loop?

  - by Chris

  I am currently designing a forum as a personal project. One of the recurring issues I've come across is database queries in loops. I've managed to avoid doing that so far by using table joins or caching of data in arrays for later use. Right now though I've come across a situation where I'm not sure how I can write the code in such a way that I can use either of those methods easily. However I'd still prefer to do at most 2 queries for this operation rather than 1 + 1 per group of forums, which so far has resulted in 5 per page. So while 5 isn't a huge number (though it will increase for each forum group I add) it's the principle that's important to me here, I do NOT want to write queries in loops What I'm doing is displaying forum index groupings (eg admin forums, user forums etc) and then each forum within that group on a single page index, it's the combination of both in one page that's causing me issue. If it had just been a single group per page, I'd use a table join and problem solved. But if I use a table join here, although I can potentially get all the data I need it'll be in one mass of results and it needs displaying properly. Here's the code (I've removed some of the html for clarity) <?php $sql= "select * from forum_groups"; //query 1 $result1 = $database->query($sql); while($group = mysql_fetch_assoc($result1)) //first loop {?> <table class="threads"> <tr> <td class="forumgroupheader"> <?php echo $group['group_name']; ?> </td> </tr> <tr> <td class="forumgroupheader2"> <?php echo $group['group_desc']; ?> </td> </tr> </table> <table> <tr> <th class="thforum"> Forum Name</th> <th class="thforum"> Forum Decsription</th> <th class="thforum"> Last Post </th> <tr> <?php $group_id = $group['id']; $sql = "SELECT forums.id, forums.forum_group_id, forums.forum_name, forums.forum_desc, forums.visible_rank, forums.locked, forums.lock_rank, forums.topics, forums.posts, forums.last_post, forums.last_post_id, users.username FROM forums LEFT JOIN users on forums.last_post_id=users.id WHERE forum_group_id='{$group_id}'"; //query 2 $result2 = $database->query($sql); while($forum = mysql_fetch_assoc($result2)) //second loop {?> So how can I either a) write the SQL in such a way as to remove the second query from inside the loop or b) combine the results in an array either way I need to be able to access the data as an when so I can format it properly for the page output, ie within the loops still.

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• Android how to match text with images by pointing text and images with lines

  - by Shirisha

  I am trying to create app which is match text with appropriate images by pointing with line. I want to create app exactly same which is shown in the below image: can any one please give me an idea? This is my main class: public class MatchActivity extends Activity { ArrayAdapter<String> listadapter; float x1; float y1; float x2; float y2; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); String[] s1 = { "smiley1", "smiley2", "smiley3" }; ListView lv = (ListView) findViewById(R.id.text_list); ArrayList<String> list = new ArrayList<String>(); list.addAll(Arrays.asList(s1)); listadapter = new ArrayAdapter<String>(this, R.layout.rowtext, s1); lv.setAdapter(listadapter); GridView gv = (GridView) findViewById(R.id.image_list); gv.setAdapter(new ImageAdapter(this)); lv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> arg0, View v, int arg2, long arg3){ x1=v.getX(); y1=v.getY(); Log.d("list","text positions x1:"+x1+" y1:"+y1); } }); gv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> arg0, View v, int arg2, long arg3){ DrawView draw=new DrawView(MatchActivity.this); x2=v.getX(); y2=v.getY(); draw.position1.add(x1); draw.position1.add(y1); draw.position2.add( x2); draw.position2.add(y2); Log.d("list","image positions x2:"+x2+" y2:"+y2); LinearLayout ll=LinearLayout)findViewById(R.id.draw_line); ll.addView(draw); } }); } } This is my drawing class to draw a line: public class DrawView extends View { Paint paint = new Paint(); private List<Float> position1=new ArrayList<Float>(); private List<Float> position2=new ArrayList<Float>();; public DrawView(Context context) { super(context); invalidate(); Log.d("drawview","In DrawView class position1:"+position1+" position2:"+position2) ; } @Override public void onDraw(Canvas canvas) { super.onDraw(canvas); Log.d("on draw","IN onDraw() position1:"+position1+" position2:"+position2); assert position1.size() == position2.size(); for (int i = 0; i < position1.size(); i += 2) { float x1 = position1.get(i); float y1 = position1.get(i + 1); float x2 = position2.get(i); float y2 = position2.get(i + 1); paint.setColor(Color.BLACK); paint.setStrokeWidth(3); canvas.drawLine(x1,y1, x2,y2, paint); } } } Thanks in advance .

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• MCV PHP Am I doing the Model right? [closed]

  - by Kosmo

  I'm trying to create a basic website using MVC in PHP to learn MVC. Its eventually going to be some sort of social networking website but right now I am trying to create a object that can create, delete, update members. What I've done so far for the Model is in the code below, I figure my Controller will take user input and build the array of data that are then passed to this Model. Am I designing this correctly? Should the Controller be the one building the Arrays? <?php class Connection { private $server; private $database; private $user; private $password; private $conn; function __construct($server, $database, $user, $password) { $this->server = $server; $this->database = $database; $this->user = $user; $this->password = $password; } function connect() { $this->conn = mysql_connect($this->server, $this->user, $this->password) or die(mysql_error()); if (!(mysql_select_db($this->database))) { throw new Exception("Could not connect to database!"); } } function deleteMember($memberId) { $queryString = "DELETE FROM Members WHERE MemberId=" . $memberId . ';'; if (!mysql_query($queryString)) { throw new Exception("Failed Deleting Member!"); } } function insertMember($columns) { $queryString = 'INSERT INTO Members'; $keys = '('; $values = '('; $count = 0; foreach($columns as $key => $value) { $keys .= $key; $values .= $value; if (!(++$count == count($columns))) { $keys .= ','; $values .= ','; } } $queryString .= $keys . ')' . ' VALUES ' . $values . ');'; if (!mysql_query($queryString, $this->conn)) { throw new Exception('Failed Inserting Member!'); } else { return mysql_insert_id(); } } function updateMember($memberId, $columns) { $queryString = 'UPDATE Members SET '; $count = 0; foreach($columns as $key => $value) { $queryString .= $key . '=' . $value; if (!(++$count == count($columns))) { $queryString .= ', '; } } $queryString .= ' WHERE MemberId=' . $memberId . ';'; if (!mysql_query($queryString)) { throw new Exception('Failed Updating Member'); } } function getMembers() { $queryString = "SELECT * FROM Members;"; $result = mysql_query($queryString); $memberArray = array(); $count = 0; while ($row = mysql_fetch_array($result)) { $memberArray[$count++] = "Member ID: " . $row['MemberId'] . " Name: " . $row['MemberName'] . " Email: " . $row['MemberEmail']; } return $memberArray; } function disconnect() { mysql_close($this->conn); } }

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• Dynamic JSON Parsing in .NET with JsonValue

  - by Rick Strahl

  So System.Json has been around for a while in Silverlight, but it's relatively new for the desktop .NET framework and now moving into the lime-light with the pending release of ASP.NET Web API which is bringing a ton of attention to server side JSON usage. The JsonValue, JsonObject and JsonArray objects are going to be pretty useful for Web API applications as they allow you dynamically create and parse JSON values without explicit .NET types to serialize from or into. But even more so I think JsonValue et al. are going to be very useful when consuming JSON APIs from various services. Yes I know C# is strongly typed, why in the world would you want to use dynamic values? So many times I've needed to retrieve a small morsel of information from a large service JSON response and rather than having to map the entire type structure of what that service returns, JsonValue actually allows me to cherry pick and only work with the values I'm interested in, without having to explicitly create everything up front. With JavaScriptSerializer or DataContractJsonSerializer you always need to have a strong type to de-serialize JSON data into. Wouldn't it be nice if no explicit type was required and you could just parse the JSON directly using a very easy to use object syntax? That's exactly what JsonValue, JsonObject and JsonArray accomplish using a JSON parser and some sweet use of dynamic sauce to make it easy to access in code. Creating JSON on the fly with JsonValue Let's start with creating JSON on the fly. It's super easy to create a dynamic object structure. JsonValue uses the dynamic  keyword extensively to make it intuitive to create object structures and turn them into JSON via dynamic object syntax. Here's an example of creating a music album structure with child songs using JsonValue:[TestMethod] public void JsonValueOutputTest() { // strong type instance var jsonObject = new JsonObject(); // dynamic expando instance you can add properties to dynamic album = jsonObject; album.AlbumName = "Dirty Deeds Done Dirt Cheap"; album.Artist = "AC/DC"; album.YearReleased = 1977; album.Songs = new JsonArray() as dynamic; dynamic song = new JsonObject(); song.SongName = "Dirty Deeds Done Dirt Cheap"; song.SongLength = "4:11"; album.Songs.Add(song); song = new JsonObject(); song.SongName = "Love at First Feel"; song.SongLength = "3:10"; album.Songs.Add(song); Console.WriteLine(album.ToString()); } This produces proper JSON just as you would expect: {"AlbumName":"Dirty Deeds Done Dirt Cheap","Artist":"AC\/DC","YearReleased":1977,"Songs":[{"SongName":"Dirty Deeds Done Dirt Cheap","SongLength":"4:11"},{"SongName":"Love at First Feel","SongLength":"3:10"}]} The important thing about this code is that there's no explicitly type that is used for holding the values to serialize to JSON. I am essentially creating this value structure on the fly by adding properties and then serialize it to JSON. This means this code can be entirely driven at runtime without compile time restraints of structure for the JSON output. Here I use JsonObject() to create a new object and immediately cast it to dynamic. JsonObject() is kind of similar in behavior to ExpandoObject in that it allows you to add properties by simply assigning to them. Internally, JsonValue/JsonObject these values are stored in pseudo collections of key value pairs that are exposed as properties through the DynamicObject functionality in .NET. The syntax gets a little tedious only if you need to create child objects or arrays that have to be explicitly defined first. Other than that the syntax looks like normal object access sytnax. Always remember though these values are dynamic - which means no Intellisense and no compiler type checking. It's up to you to ensure that the values you create are accessed consistently and without typos in your code. Note that you can also access the JsonValue instance directly and get access to the underlying type. This means you can assign properties by string, which can be useful for fully data driven JSON generation from other structures. Below you can see both styles of access next to each other:// strong type instance var jsonObject = new JsonObject(); // you can explicitly add values here jsonObject.Add("Entered", DateTime.Now); // expando style instance you can just 'use' properties dynamic album = jsonObject; album.AlbumName = "Dirty Deeds Done Dirt Cheap"; JsonValue internally stores properties keys and values in collections and you can iterate over them at runtime. You can also manipulate the collections if you need to to get the object structure to look exactly like you want. Again, if you've used ExpandoObject before JsonObject/Value are very similar in the behavior of the structure. Reading JSON strings into JsonValue The JsonValue structure supports importing JSON via the Parse() and Load() methods which can read JSON data from a string or various streams respectively. Essentially JsonValue includes the core JSON parsing to turn a JSON string into a collection of JsonValue objects that can be then referenced using familiar dynamic object syntax. Here's a simple example:[TestMethod] public void JsonValueParsingTest() { var jsonString = @"{""Name"":""Rick"",""Company"":""West Wind"",""Entered"":""2012-03-16T00:03:33.245-10:00""}"; dynamic json = JsonValue.Parse(jsonString); // values require casting string name = json.Name; string company = json.Company; DateTime entered = json.Entered; Assert.AreEqual(name, "Rick"); Assert.AreEqual(company, "West Wind"); } The JSON string represents an object with three properties which is parsed into a JsonValue object and cast to dynamic. Once cast to dynamic I can then go ahead and access the object using familiar object syntax. Note that the actual values - json.Name, json.Company, json.Entered - are actually of type JsonPrimitive and I have to assign them to their appropriate types first before I can do type comparisons. The dynamic properties will automatically cast to the right type expected as long as the compiler can resolve the type of the assignment or usage. The AreEqual() method oesn't as it expects two object instances and comparing json.Company to "West Wind" is comparing two different types (JsonPrimitive to String) which fails. So the intermediary assignment is required to make the test pass. The JSON structure can be much more complex than this simple example. Here's another example of an array of albums serialized to JSON and then parsed through with JsonValue():[TestMethod] public void JsonArrayParsingTest() { var jsonString = @"[ { ""Id"": ""b3ec4e5c"", ""AlbumName"": ""Dirty Deeds Done Dirt Cheap"", ""Artist"": ""AC/DC"", ""YearReleased"": 1977, ""Entered"": ""2012-03-16T00:13:12.2810521-10:00"", ""AlbumImageUrl"": ""http://ecx.images-amazon.com/images/I/61kTaH-uZBL._AA115_.jpg"", ""AmazonUrl"": ""http://www.amazon.com/gp/product/B00008BXJ4/ref=as_li_ss_tl?ie=UTF8&tag=westwindtechn-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B00008BXJ4"", ""Songs"": [ { ""AlbumId"": ""b3ec4e5c"", ""SongName"": ""Dirty Deeds Done Dirt Cheap"", ""SongLength"": ""4:11"" }, { ""AlbumId"": ""b3ec4e5c"", ""SongName"": ""Love at First Feel"", ""SongLength"": ""3:10"" }, { ""AlbumId"": ""b3ec4e5c"", ""SongName"": ""Big Balls"", ""SongLength"": ""2:38"" } ] }, { ""Id"": ""67280fb8"", ""AlbumName"": ""Echoes, Silence, Patience & Grace"", ""Artist"": ""Foo Fighters"", ""YearReleased"": 2007, ""Entered"": ""2012-03-16T00:13:12.2810521-10:00"", ""AlbumImageUrl"": ""http://ecx.images-amazon.com/images/I/41mtlesQPVL._SL500_AA280_.jpg"", ""AmazonUrl"": ""http://www.amazon.com/gp/product/B000UFAURI/ref=as_li_ss_tl?ie=UTF8&tag=westwindtechn-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B000UFAURI"", ""Songs"": [ { ""AlbumId"": ""67280fb8"", ""SongName"": ""The Pretender"", ""SongLength"": ""4:29"" }, { ""AlbumId"": ""67280fb8"", ""SongName"": ""Let it Die"", ""SongLength"": ""4:05"" }, { ""AlbumId"": ""67280fb8"", ""SongName"": ""Erase/Replay"", ""SongLength"": ""4:13"" } ] }, { ""Id"": ""7b919432"", ""AlbumName"": ""End of the Silence"", ""Artist"": ""Henry Rollins Band"", ""YearReleased"": 1992, ""Entered"": ""2012-03-16T00:13:12.2800521-10:00"", ""AlbumImageUrl"": ""http://ecx.images-amazon.com/images/I/51FO3rb1tuL._SL160_AA160_.jpg"", ""AmazonUrl"": ""http://www.amazon.com/End-Silence-Rollins-Band/dp/B0000040OX/ref=sr_1_5?ie=UTF8&qid=1302232195&sr=8-5"", ""Songs"": [ { ""AlbumId"": ""7b919432"", ""SongName"": ""Low Self Opinion"", ""SongLength"": ""5:24"" }, { ""AlbumId"": ""7b919432"", ""SongName"": ""Grip"", ""SongLength"": ""4:51"" } ] } ]"; dynamic albums = JsonValue.Parse(jsonString); foreach (dynamic album in albums) { Console.WriteLine(album.AlbumName + " (" + album.YearReleased.ToString() + ")"); foreach (dynamic song in album.Songs) { Console.WriteLine("\t" + song.SongName ); } } Console.WriteLine(albums[0].AlbumName); Console.WriteLine(albums[0].Songs[1].SongName);}   It's pretty sweet how easy it becomes to parse even complex JSON and then just run through the object using object syntax, yet without an explicit type in the mix. In fact it looks and feels a lot like if you were using JavaScript to parse through this data, doesn't it? And that's the point…© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  Web Api  JSON   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Parallelism in .NET – Part 11, Divide and Conquer via Parallel.Invoke

  - by Reed

  Many algorithms are easily written to work via recursion.  For example, most data-oriented tasks where a tree of data must be processed are much more easily handled by starting at the root, and recursively “walking” the tree.  Some algorithms work this way on flat data structures, such as arrays, as well.  This is a form of divide and conquer: an algorithm design which is based around breaking up a set of work recursively, “dividing” the total work in each recursive step, and “conquering” the work when the remaining work is small enough to be solved easily. Recursive algorithms, especially ones based on a form of divide and conquer, are often a very good candidate for parallelization. This is apparent from a common sense standpoint.  Since we’re dividing up the total work in the algorithm, we have an obvious, built-in partitioning scheme.  Once partitioned, the data can be worked upon independently, so there is good, clean isolation of data. Implementing this type of algorithm is fairly simple.  The Parallel class in .NET 4 includes a method suited for this type of operation: Parallel.Invoke.  This method works by taking any number of delegates defined as an Action, and operating them all in parallel.  The method returns when every delegate has completed: Parallel.Invoke( () => { Console.WriteLine("Action 1 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); }, () => { Console.WriteLine("Action 2 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); }, () => { Console.WriteLine("Action 3 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); } ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Running this simple example demonstrates the ease of using this method.  For example, on my system, I get three separate thread IDs when running the above code.  By allowing any number of delegates to be executed directly, concurrently, the Parallel.Invoke method provides us an easy way to parallelize any algorithm based on divide and conquer.  We can divide our work in each step, and execute each task in parallel, recursively. For example, suppose we wanted to implement our own quicksort routine.  The quicksort algorithm can be designed based on divide and conquer.  In each iteration, we pick a pivot point, and use that to partition the total array.  We swap the elements around the pivot, then recursively sort the lists on each side of the pivot.  For example, let’s look at this simple, sequential implementation of quicksort: public static void QuickSort<T>(T[] array) where T : IComparable<T> { QuickSortInternal(array, 0, array.Length - 1); } private static void QuickSortInternal<T>(T[] array, int left, int right) where T : IComparable<T> { if (left >= right) { return; } SwapElements(array, left, (left + right) / 2); int last = left; for (int current = left + 1; current <= right; ++current) { if (array[current].CompareTo(array[left]) < 0) { ++last; SwapElements(array, last, current); } } SwapElements(array, left, last); QuickSortInternal(array, left, last - 1); QuickSortInternal(array, last + 1, right); } static void SwapElements<T>(T[] array, int i, int j) { T temp = array[i]; array[i] = array[j]; array[j] = temp; } Here, we implement the quicksort algorithm in a very common, divide and conquer approach.  Running this against the built-in Array.Sort routine shows that we get the exact same answers (although the framework’s sort routine is slightly faster).  On my system, for example, I can use framework’s sort to sort ten million random doubles in about 7.3s, and this implementation takes about 9.3s on average. Looking at this routine, though, there is a clear opportunity to parallelize.  At the end of QuickSortInternal, we recursively call into QuickSortInternal with each partition of the array after the pivot is chosen.  This can be rewritten to use Parallel.Invoke by simply changing it to: // Code above is unchanged... SwapElements(array, left, last); Parallel.Invoke( () => QuickSortInternal(array, left, last - 1), () => QuickSortInternal(array, last + 1, right) ); } This routine will now run in parallel.  When executing, we now see the CPU usage across all cores spike while it executes.  However, there is a significant problem here – by parallelizing this routine, we took it from an execution time of 9.3s to an execution time of approximately 14 seconds!  We’re using more resources as seen in the CPU usage, but the overall result is a dramatic slowdown in overall processing time. This occurs because parallelization adds overhead.  Each time we split this array, we spawn two new tasks to parallelize this algorithm!  This is far, far too many tasks for our cores to operate upon at a single time.  In effect, we’re “over-parallelizing” this routine.  This is a common problem when working with divide and conquer algorithms, and leads to an important observation: When parallelizing a recursive routine, take special care not to add more tasks than necessary to fully utilize your system. This can be done with a few different approaches, in this case.  Typically, the way to handle this is to stop parallelizing the routine at a certain point, and revert back to the serial approach.  Since the first few recursions will all still be parallelized, our “deeper” recursive tasks will be running in parallel, and can take full advantage of the machine.  This also dramatically reduces the overhead added by parallelizing, since we’re only adding overhead for the first few recursive calls.  There are two basic approaches we can take here.  The first approach would be to look at the total work size, and if it’s smaller than a specific threshold, revert to our serial implementation.  In this case, we could just check right-left, and if it’s under a threshold, call the methods directly instead of using Parallel.Invoke. The second approach is to track how “deep” in the “tree” we are currently at, and if we are below some number of levels, stop parallelizing.  This approach is a more general-purpose approach, since it works on routines which parse trees as well as routines working off of a single array, but may not work as well if a poor partitioning strategy is chosen or the tree is not balanced evenly. This can be written very easily.  If we pass a maxDepth parameter into our internal routine, we can restrict the amount of times we parallelize by changing the recursive call to: // Code above is unchanged... SwapElements(array, left, last); if (maxDepth < 1) { QuickSortInternal(array, left, last - 1, maxDepth); QuickSortInternal(array, last + 1, right, maxDepth); } else { --maxDepth; Parallel.Invoke( () => QuickSortInternal(array, left, last - 1, maxDepth), () => QuickSortInternal(array, last + 1, right, maxDepth)); } We no longer allow this to parallelize indefinitely – only to a specific depth, at which time we revert to a serial implementation.  By starting the routine with a maxDepth equal to Environment.ProcessorCount, we can restrict the total amount of parallel operations significantly, but still provide adequate work for each processing core. With this final change, my timings are much better.  On average, I get the following timings: Framework via Array.Sort: 7.3 seconds Serial Quicksort Implementation: 9.3 seconds Naive Parallel Implementation: 14 seconds Parallel Implementation Restricting Depth: 4.7 seconds Finally, we are now faster than the framework’s Array.Sort implementation.

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