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• Comparing all values within a List against each other

  - by Kave

  I am a bit stuck here and can't think further. public struct CandidateDetail { public int CellX { get; set; } public int CellY { get; set; } public int CellId { get; set; } } var dic = new Dictionary<int, List<CandidateDetail>>(); How can I compare each CandidateDetail item against other CandidateDetail items within the same dictionary in the most efficient way? Example: There are three keys for the dictionary: 5, 6 and 1. Therefore we have three entries. now each of these key entries would have a List associated with. In this case let say each of these three numbers has exactly two CandidateDetails items within the list associated to each key. This means in other words we have two 5, two 6 and two 1 in different or in the same cells. I would like to know: if[5].1stItem.CellId == [6].1stItem.CellId = we got a hit. That means we have a 5 and a 6 within the same Cell if[5].2ndItem.CellId == [6].2ndItem.CellId = perfect. We found out that the other 5 and 6 are together within a different cell. if[1].1stItem.CellId == ... Now I need to check the 1 also against the other 5 and 6 to see if the one exists within the previous same two cells or not. Could a Linq expression help perhaps? I am quite stuck here... I don't know...Maybe I am taking the wrong approach. I am trying to solve the "Hidden pair" of the game Sudoku. :) http://www.sudokusolver.eu/ExplainSolveMethodD.aspx Many Thanks, Kave

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• getchar does not stop when using scanf

  - by Oz123

  I am have a difficulty understanding getchar(). In the following program getchar works as expected: #include <stdio.h> int main() { printf("Type Enter to continue..."); getchar(); return 0; } However, in the following program, getchar does not create a delay and the program ends: #include <stdio.h> int main() { char command[100]; scanf("%s", command ); printf("Type Enter to continue..."); getchar(); return 0; } I have the following weired workaround, which works, but I understand why: #include <stdio.h> int main() { char command[100]; int i; scanf("%s", command ); printf("Type Enter to continue..."); while ( getchar() != '\n') { i=0; } getchar(); return 0; } So my questions are: 1. What is scanf doing? Why does scanf do this ? 2. Why is my work around working? 3. What is a good way to emulate the following Python code: raw_input("Type Enter to continue")

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• Communication between parent and child

  - by Pierre

  Hi every one ! I have a little problem. I have to code a simple C application that creat a process and his child (fork()) and I have to do an operation. Parent initialize the values and child calculate. I write this : #include #include #include #include #include typedef struct { int op1; char op; int op2; }Operation; Operation *varOP; void finalResult() { float result = 0; if(varOP-op == '+') result = (varOP-op1 + varOP-op2); if(varOP-op == '-') result = (varOP-op1 - varOP-op2); if(varOP-op == '*') result = (varOP-op1 * varOP-op2); if(varOP-op == '+') result = (varOP-op1 / varOP-op2); printf("%f",result); } int main () { int p; varOP = (Operation *)malloc(sizeof(Operation)); p = fork(); if(p == 0) // If child { signal(SIGUSR1, finalResult ); pause(); } if(p 0) // If parent { varOP-op = '+'; varOP-op1 = 2; varOP-op2 = 3; kill(p, SIGUSR1); wait(NULL); } return 0; } But my child is never called. Is there something wrong with my code? Thanks for your help !

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• Project Euler Problem #11

  - by SoulBeaver

  Source: http://projecteuler.net/index.php?section=problems&id=11 Quick overview: Take a 20x20 grid of numbers and compute the largest product of 4 pairs of numbers in either horizontal, vertical, or diagonal. My current approach is to divide the 20x20 grid up into single rows and single columns and go from there with a much more manageable grid. The code I'm using to divide the rows into rows is void fillRows ( string::const_iterator& fieldIter, list<int>& rowElements, vector<list<int>>& rows ) { int count(0); for( ; fieldIter < field.end(); ++fieldIter ) { if(isdigit(field[*fieldIter])) { rowElements.push_back(toInt(field[*fieldIter])); ++count; } if(count == 40) { rows.push_back(rowElements); count = 0; rowElements.clear(); } } } Short explanation: I have the field set as static const std::string field and I am filling a vector with lists of rows. Why a list? Because the queue doesn't have a clear function. Also practice using STL container lists and not ones I write myself. However, this thing isn't working. Oftentimes I see it omitting a character( function toInt parses the const char as int ) and I end up with 18 rows, two rows short of the 20x20 grid. The length of the rows seem good. Rows: 18 RowElements[0]: 40 (instead of pairs I saved each number individually. Will fix that later) What am I doing wrong?

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• Why wont this compile its killing me. (java)

  - by Ryan The Leach

  import java.util.*; public class Caesar { public static void main(String [] args) { final boolean DEBUG = false; System.out.println("Welcome to the Caesar Cypher"); System.out.println("----------------------------"); Scanner keyboard = new Scanner (System.in); System.out.print("Enter a String : "); String plainText = keyboard.nextLine(); System.out.print("Enter an offset: "); int offset = keyboard.nextInt(); String cipherText = ""; for(int i=0;i<plainText.length();i++) { int chVal = plainText.charAt(i); if (DEBUG) {int debugchVal = chVal;} chVal +=offset; if (DEBUG) {System.out.print(chVal + "\t");} while (chVal <32 || chVal > 127) { if (chVal < 32) chVal += 96; if (chVal > 127) chVal -= 96; if(DEBUG) {System.out.print(chVal+" ");} } if (DEBUG) {System.out.println();} char c = (char) chVal; cipherText = cipherText + c; if (DEBUG) {System.out.println(i + "\t" + debugchVal + "\t" + chVal + "\t" + c + "\t" + cipherText);} } System.out.println(cipherText); } }

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• Dynamic checkboxlist

  - by Steve

  Hi, I am currently building a dynamic url tab system that user can say what urls they want to be displayed on a tabpage control. In the database i have the following columns. userID, int URLName var Enabled bit I am pulling the data back ok but what i am trying do is populate a checkbox list with the urlname and its status on a user options page so they can say what tabs they want displayed. I have wrote the following methods to get the urls and create the checkboxes however i keep getting the following error. ex = {"InvalidArgument=Value of '1' is not valid for 'index'.\r\nParameter name: index"} It reads the first row ok but when it hits the 2nd row that is being returned i get that error. Has anyone got any ideas? Thanks private void GetUserURLS() { db.initiateCommand("[Settings].[LoadAllUserURLS]", CommandType.StoredProcedure); sqlp = db.addParameter("@UserID", _UserID, SqlDbType.Int, ParameterDirection.Input); sqlp = db.addParameter("@spErrorID", DBNull.Value, SqlDbType.Int, ParameterDirection.InputOutput); db.executeCommand(); CreateCheckBoxes(db.getTable(0).Rows); db.releaseCommand(); } private void CreateCheckBoxes(DataRowCollection rows) { try { int i = 0; foreach (DataRow row in rows) { //Gets the url name and path when the status is enabled. The status of Enabled / Disabled is setup in the users option page string URLName = row["URLName"].ToString(); bool enabled = Convert.ToBoolean(row["Enabled"]); CheckedListBox CB = new CheckedListBox(); CB.Items.Insert(i, URLName); CB.Tag = "CB" + i.ToString(); checkedListBox1.Items.Add(CB); i++; } } catch (Exception ex) { //Log error Functionality func = new Functionality(); func.LogError(ex); //Error message the user will see string FriendlyError = "There has been populating checkboxes with the urls - A notification has been sent to development"; Classes.ShowMessageBox.MsgBox(FriendlyError, "There has been an Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } }

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• Why won't this println command start a new line?

  - by David

  Here's the relevant code: public static void printBoarders (Territory x) { int t = 0 ; int n = 0 ; for (int i = 0; i<x.borders.length; i++) { if (x.borders[i] == -1) t = i ; } for (int j = 0; j<x.borders.length; j++) { if (x.borders[j] == 1) n++ ; } Territory.translate (t) ; System.out.print (" has " + n + " borders: ") ; Territory.translate (x.borders) ; System.out.println (" ") ; } When I run this, I get everything on one line without a line break. Why isn't the System.out.println (" ") ; creating a line break? Here is an example of what the output winds up being: Northwest Territory, Alberta, Kamchatka, hidavid-names-macbook-pro:~ davidname$ EDIT: the problem was that this method was never being invoked. A different one which i was replacing was. All is well.

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• seg fault at the end of program after executing everything?

  - by Fantastic Fourier

  Hello all, I wrote a quick program which executes every statement before giving a seg fault error. struct foo { int cat; int * dog; }; void bar (void * arg) { printf("o hello bar\n"); struct foo * food = (struct foo *) arg; printf("cat meows %i\n", food->cat); printf("dog barks %i\n", *(food->dog)); } void main() { int cat = 4; int * dog; dog = &cat; printf("cat meows %i\n", cat); printf("dog barks %i\n", *dog); struct foo * food; food->cat = cat; food->dog = dog; printf("cat meows %i\n", food->cat); printf("dog barks %i\n", *(food->dog)); printf("time for foo!\n"); bar(food); printf("begone!\n"); cat = 5; printf("cat meows %i\n", cat); printf("dog barks %i\n", *dog); // return 0; } which gives a result of cat meows 4 dog barks 4 cat meows 4 dog barks 4 time for foo! o hello bar cat meows 4 dog barks 4 begone! cat meows 5 dog barks 5 Segmentation fault (core dumped) I'm not really sure why it seg faults at the end? Any comments/insights are deeply appreciated.

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• animated swap position of two buttons

  - by Jagat

  I am trying to swap the position of two buttons. my swapping code looks as below. private void exchangeButtons(Button btn1, Button btn2) { // Create the animation set AnimationSet exchangeAnimation = new AnimationSet(true); TranslateAnimation translate = new TranslateAnimation( Animation.RELATIVE_TO_SELF, btn2.getLeft(), Animation.RELATIVE_TO_SELF, btn1.getLeft(), Animation.RELATIVE_TO_SELF, btn2.getRight(), Animation.RELATIVE_TO_SELF, btn1.getRight() ); translate.setDuration(500); exchangeAnimation.addAnimation(translate); // int fromX = btn1.getLeft(); // int fromY = btn1.getRight(); // int toX = btn2.getLeft(); // int toY = btn2.getRight(); Log.d("ArrangeMe", "view1 pos:" + btn1.getLeft() + ", " +btn1.getRight() + "view2 pos:" + btn2.getLeft() + ", " + btn2.getRight()); AnimationSet exchangeAnimation1 = new AnimationSet(true); TranslateAnimation translate1 = new TranslateAnimation( Animation.RELATIVE_TO_SELF, btn1.getLeft(), Animation.RELATIVE_TO_SELF, btn2.getLeft(), Animation.RELATIVE_TO_SELF, btn1.getRight(), Animation.RELATIVE_TO_SELF, btn2.getRight() ); translate1.setDuration(500); exchangeAnimation1.addAnimation(translate1); // EXECUTE btn1.startAnimation(exchangeAnimation); btn2.startAnimation(exchangeAnimation1); } I call the code as below exchangeButtons(button1, button2); my layout looks as below what happens when i execute the code is, instead of the buttons exchanging their positions, they just disappear for sometime[may be 500 ms] and reappear as they were originally. how to resolve this problem ? will it work properly in device ? regards

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• Why does gcc generate verbose assembly code?

  - by Jared Nash

  I have a question about assembly code generated by GCC (-S option). Since, I am new to assembly language and know very little about it, the question will be very primitive. Still, I hope somebody will answer: Suppose, I have this C code: main(){ int x = 15; int y = 6; int z = x - y; return 0; } If we look at the assembly code (especially the part corresponding to int z = x - y ), we see: main: ... subl $16, %esp movl $15, -4(%ebp) movl $6, -8(%ebp) movl -8(%ebp), %eax movl -4(%ebp), %edx movl %edx, %ecx subl %eax, %ecx movl %ecx, %eax movl %eax, -12(%ebp) ... Why doesn't GCC generate something like this, which is less copying things around. main: ... movl $15, -4(%ebp) movl $6, -8(%ebp) movl -8(%ebp), %edx movl -4(%ebp), %eax subl %edx, %eax movl %eax, -12(%ebp) ... P.S. Linux zion-5 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i686 GNU/Linux gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)

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• Can't Display Bitmap of Higher Resolution than CDC area

  - by T. Jones

  Hi there dear gurus and expert coders. i am not gonna start with im a newbie and don't know much about image programming but unfortunately those are the facts :( I am trying to display an image from a bitmap pointer *ImageData which is of resolution 1392x1032. I am trying to draw that at an area of resolution or size 627x474. However, repeated trying doesnt seem to work. It works when I change the bitmap image I created from *ImageData width and height to resolution or size of around 627x474 I really do not know how to solve this after trying all possible solutions from various forums and google. pDC is a CDC* and memDC is a CDC initialized in an earlier method Anything uninitialized here was initialized in other methods. Here is my code dear humble gurus. Do provide me with guidance Yoda and Obi-Wan provided to Luke Skywalker. void DemoControl::ShowImage( void *ImageData ) { int Width; //Width of Image From Camera int Height; //Height of Image From Camera int m_DisplayWidth = 627 ;//width of rectangle area to display int m_DisplayHeight = 474;//height of rectangle area to display GetImageSize( &Width, &Height ) ; //this will return Width = 1392, Height 1032 CBitmap bitmap; bitmap.CreateBitmap(Width,Height,32,1,ImageData); CBitmap* pOldBitmap = memDC.SelectObject((CBitmap*)&bitmap); pDC->BitBlt(22, 24, 627, 474, &memDC, 0, 0, SRCCOPY); memDC.SelectObject((CBitmap*)pOldBitmap); ReleaseDC(pDC); }

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• Trying to set up nested while loops using a boolean switch

  - by thorn100

  First time posting. I'm trying to set up a while loop that will ask the user for the employee name, hours worked and hourly wage until the user enters 'DONE'. Eventually I'll modify the code to calculate the weekly pay and write it to a list, but one thing at a time. The problem is once the main while loop executes once, it just stops. Doesn't error out but just stops. I have to kill the program to get it to stop. I want it to ask the three questions again and again until the user is finished. Thoughts? Please note that this is just an exercise and not meant for any real world application. def getName(): """Asks for the employee's full name""" firstName=raw_input("\nWhat is your first name? ") lastName=raw_input("\nWhat is your last name? ") fullName=firstName.title() + " " + lastName.title() return fullName def getHours(): """Asks for the number of hours the employee worked""" hoursWorked=0 while int(hoursWorked)<1 or int(hoursWorked) > 60: hoursWorked=raw_input("\nHow many hours did the employee work: ") if int(hoursWorked)<1 or int(hoursWorked) > 60: print "Please enter an integer between 1 and 60." else: return hoursWorked def getWage(): """Asks for the employee's hourly wage""" wage=0 while float(wage)<6.00 or float(wage)>20.00: wage=raw_input("\nWhat is the employee's hourly wage: ") if float(wage)<6.00 or float(wage)>20.00: print ("Please enter an hourly wage between $6.00 and $20.00") else: return wage ##sentry variables employeeName="" employeeHours=0 employeeWage=0 booleanDone=False #Enter employee info print "Please enter payroll information for an employee or enter 'DONE' to quit." while booleanDone==False: while employeeName=="": employeeName=getName() if employeeName.lower()=="done": booleanDone=True break print "The employee's name is", employeeName while employeeHours==0: employeeHours=getHours() if employeeHours.lower()=="done": booleanDone=True break print employeeName, "worked", employeeHours, "this week." while employeeWage==0: employeeWage=getWage() if employeeWage.lower()=="done": booleanDone=True break print employeeName + "'s hourly wage is $" + employeeWage

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• FILE* issue PPU side code

  - by Cristina

  We are working on a homework on CELL programming for college and their feedback response to our questions is kinda slow, thought i can get some faster answers here. I have a PPU side code which tries to open a file passed down through char* argv[], however this doesn't work it cannot make the assignment of the pointer, i get a NULL. Now my first idea was that the file isn't in the correct directory and i copied in every possible and logical place, my second idea is that maybe the PPU wants this pointer in its LS area, but i can't deduce if that's the bug or not. So... My question is what am i doing wrong? I am working with a Fedora 7 SDK Cell, with Eclipse as an IDE. Maybe my argument setup is wrong tho he gets the name of the file correctly. Code on request: images_t *read_bin_data(char *name) { FILE *file; images_t *img; uint32_t *buffer; uint8_t buf; unsigned long fileLen; unsigned long i; //Open file file = (FILE*)malloc(sizeof(FILE)); file = fopen(name, "rb"); printf("[Debug]Opening file %s\n",name); if (!file) { fprintf(stderr, "Unable to open file %s", name); return NULL; } //....... } Main launch: int main(int argc,char* argv[]) { int i,img_width; int modif_this[4] __attribute__ ((aligned(16))) = {1,2,3,4}; images_t *faces, *nonfaces; spe_context_ptr_t ctxs[SPU_THREADS]; pthread_t threads[SPU_THREADS]; thread_arg_t arg[SPU_THREADS]; //intializare img_width img_width = atoi(argv[1]); printf("[Debug]Img size is %i\n",img_width); faces = read_bin_data(argv[3]); //....... } Thanks for the help.

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• Issue in setting alarm time in AlarmManager Class

  - by Anshuman

  I have used the following code in setting alarm time in AlarmManager class. Now Suppose my device current date 9-july-2012 11:31:00, Now suppose i set set a alarm at 9-july-2012 11:45:00, then it works fine and pop-up an alarm at that time. But if i set an alarm at 10-aug-2012 11:40:00, then as soon as exit the app the alarm pop-up, which is wrong because i set an alarm at month of august, So why this happen, is anything wrong in my code. if anyone knows help me to solve this out. Code For Setting Alarm time in AlarmManager class Intent myIntent = new Intent(context, AlarmService.class); PendingIntent pendingIntent = PendingIntent.getService(context, i, myIntent, i); AlarmManager alarmManager = (AlarmManager)context.getSystemService(AlarmService.ALARM_SERVICE); Calendar calendar = Calendar.getInstance(); calendar.setTimeInMillis(System.currentTimeMillis()); calendar.add(Calendar.MILLISECOND, (int) dateDifferenceFromSystemTime(NoteManager.getSingletonObject().getAlarmTime(i))); alarmManager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent); public static long dateDifferenceFromSystemTime(Date date) { long difference = 0; try { Calendar c = Calendar.getInstance(); difference = date.getTime() - c.getTimeInMillis(); if (difference < 0) { // if difference is -1 - means alarm time is of previous time then current // then firstly change it to +positive and subtract form 86400000 to get exact new time to play alarm // 86400000-Total no of milliseconds of 24hr Day difference = difference * -1; difference = 86400000 - difference; } } catch (Exception e) { e.printStackTrace(); } return difference; } Service class which pop-up alarm when matches time public class AlarmService extends IntentService { public void onCreate() { super.onCreate(); } public AlarmService() { super("MyAlarmService"); } @Override public int onStartCommand(Intent intent, int flags, int startId) { super.onStartCommand(intent, startId, startId); return START_STICKY; } @Override protected void onHandleIntent(Intent intent) { startActivity(new Intent(this,AlarmDialogActivity.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK)); } }

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• How to produce output using show function.

  - by wilson88

  I am trying to use sho to show the output of another function.The first function was used to do sorting, and returned a List. now I want to make a function that uses show() to display the output.This is how I had tried it only to get an error. Its to diplay the results of two the two sorted lists which used this function. map Auctioneer::compareBidList(map& one, map& two) and //**return Sorted.** void show(const char *msg, map<int, Bid*>& Sorted) { cout << msg << endl; show(Sorted); } void compare(map<int, Bid*>& sellers, map<int, Bid*>& buyers) { compare(sellers.begin(), sellers.end(), buyers.begin(),buyers.end(),compareBidList); } //my call in the main after declaration was as follows map<int, Bid*> buyers, sellers; Auctioneer auctioneer; auctioneer.compare(sellers,buyers); show(("Bids after sorting:", sellers,buyers);)

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• read text file in xcode

  - by danielDhobbs

  hello. i tried to read text file in xcode but this "EXC_BAD_ACCESS message showed up when i tried to build my program here is my code and i put inputA.txt file in the same folder with project file my friend told me that i should put txt file in debug folder is this why i cannot read txt file in this code? please help me... macbook user. int main (int argc, const char * argv[]) { FILE* fp; char mychar; char arr[50][2] = {0, }; int i = 0; int j, k; graphType* G_; G_ = (graphType*)malloc(sizeof(graphType)); Create(G_); fp = fopen("inputA.txt", "r"); //fp = fopen("inputB.txt", "r"); //fp = fopen("inputC.txt", "r"); while(1){ for(j = 0 ; j < 2 ; j++){ mychar = fgetc(fp); if(mychar == EOF) break; else if(mychar == ' ') continue; arr[i][j] = mychar; } i++; }

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• Problem using structured data with sproxy-generated proxy c++ class

  - by Odrade

  I am attempting to communicate structured data types between a Visual C++ client application and an ASP.NET web service. I'm am having issues whenever any parameter or return type is not a basic type (e.g. string, int, float, etc). To illustrate the issue, I created the following ASP.NET web service: namespace TestWebService { [WebService(Namespace = "http://localhost/TestWebService")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [ToolboxItem(false)] public class Service1 : System.Web.Services.WebService { [WebMethod] public TestData StructuredOutput() { TestData td = new TestData(); td.data = 1729; return td; } } public class TestData { public int data; } } To consume the service, I created a dirt-simple Visual C++ client in VS2005. I added a web reference to the project, which caused sproxy to generate a proxy class for me. With the generated header properly included, I attempted to invoke the service like this: int _tmain(int argc, _TCHAR* argv[]) { CoInitialize(NULL); Service1::CService1 ws; Service1::TestData td; HRESULT hr = ws.StructuredOutput(&td); //data is returned as expected CoUninitialize(); return 0; } // crashes here with access violation The call to StructuredOutput returns the data as expected, but an access violation occurs on destruction of the CService1 object. The access violation is occurring here (from atlsoap.h): void UninitializeSOAP() { if (m_spReader.p != NULL) { m_spReader->putContentHandler(NULL); //access violation m_spReader.Release(); } } I see the same behavior when using a TestData object as an input parameter, or when using any other structured data types as input or output. When I use basic types for input/output from the web service I do not experience these errors. Any ideas about why this might be happening? Is sproxy screwing something up, or am I? NOTE: I'm aware of gSOAP and the wsdl2h tool, but those aren't freely available for commercial use (and nobody here is going to buy a license). I am open to alternatives for generating the c++ proxy, as long as they are free for commercial use.

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• Is it normal for C++ static initialization to appear twice in the same backtrace?

  - by Joseph Garvin

  I'm trying to debug a C++ program compiled with GCC that freezes at startup. GCC mutex protects function's static local variables, and it appears that waiting to acquire such a lock is why it freezes. How this happens is rather confusing. First module A's static initialization occurs (there are __static_init functions GCC invokes that are visible in the backtrace), which calls a function Foo(), that has a static local variable. The static local variable is an object who's constructor calls through several layers of functions, then suddenly the backtrace has a few ??'s, and then it's is in the static initialization of a second module B (the __static functions occur all over again), which then calls Foo(), but since Foo() never returned the first time the mutex on the local static variable is still set, and it locks. How can one static init trigger another? My first theory was shared libraries -- that module A would be calling some function in module B that would cause module B to load, thus triggering B's static init, but that doesn't appear to be the case. Module A doesn't use module B at all. So I have a second (and horrifying) guess. Say that: Module A uses some templated function or a function in a templated class, e.g. foo<int>::bar() Module B also uses foo<int>::bar() Module A doesn't depend on module B at all At link time, the linker has two instances of foo<int>::bar(), but this is OK because template functions are marked as weak symbols... At runtime, module A calls foo<int>::bar, and the static init of module B is triggered, even though module B doesn't depend on module A! Why? Because the linker decided to go with module B's instance of foo::bar instead of module A's instance at link time. Is this particular scenario valid? Or should one module's static init never trigger static init in another module?

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• Access cost of dynamically created objects with dynamically allocated members

  - by user343547

  I'm building an application which will have dynamic allocated objects of type A each with a dynamically allocated member (v) similar to the below class class A { int a; int b; int* v; }; where: The memory for v will be allocated in the constructor. v will be allocated once when an object of type A is created and will never need to be resized. The size of v will vary across all instances of A. The application will potentially have a huge number of such objects and mostly need to stream a large number of these objects through the CPU but only need to perform very simple computations on the members variables. Could having v dynamically allocated could mean that an instance of A and its member v are not located together in memory? What tools and techniques can be used to test if this fragmentation is a performance bottleneck? If such fragmentation is a performance issue, are there any techniques that could allow A and v to allocated in a continuous region of memory? Or are there any techniques to aid memory access such as pre-fetching scheme? for example get an object of type A operate on the other member variables whilst pre-fetching v. If the size of v or an acceptable maximum size could be known at compile time would replacing v with a fixed sized array like int v[max_length] lead to better performance? The target platforms are standard desktop machines with x86/AMD64 processors, Windows or Linux OSes and compiled using either GCC or MSVC compilers.

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• error LNK2001: unresolved external symbol

  - by numerical25

  I am receiving this error >GXRenderManager.obj : error LNK2001: unresolved external symbol "private: static class GXRenderer * GXRenderManager::renderDevice" (?renderDevice@GXRenderManager@@0PAVGXRenderer@@A) The following is my code... GXDX.h class GXDX: public GXRenderer { public: void Render(); void StartUp(); }; GXGL.h class GXGL: public GXRenderer { public: void Render(); void StartUp(); }; GXRenderer class GXRenderer { public: virtual void Render() = 0; virtual void StartUp() = 0; }; GXRenderManager.h #ifndef GXRM #define GXRM #include <windows.h> #include "GXRenderer.h" #include "GXDX.h" #include "GXGL.h" enum GXDEVICE { DIRECTX, OPENGL }; class GXRenderManager { public: static int Ignite(GXDEVICE); private: static GXRenderer *renderDevice; }; #endif GXRenderManager.cpp #include "GXRenderManager.h" int GXRenderManager::Ignite(GXDEVICE DeviceType) { switch(DeviceType) { case DIRECTX: GXRenderManager::renderDevice = new GXDX; return 1; break; case OPENGL: GXRenderManager::renderDevice = new GXGL; return 1; break; default: return 0; } } main.cpp #include "GXRenderManager.h" int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { return 0; } I am not trying to get it to do anything. I am just trying to compile with no errors. I am new with all this so if anyone can give me a hand. that will be great. thanks

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• Threading is slow and unpredictable?

  - by Jake

  I've created the basis of a ray tracer, here's my testing function for drawing the scene: public void Trace(int start, int jump, Sphere testSphere) { for (int x = start; x < scene.SceneWidth; x += jump) { for (int y = 0; y < scene.SceneHeight; y++) { Ray fired = Ray.FireThroughPixel(scene, x, y); if (testSphere.Intersects(fired)) sceneRenderer.SetPixel(x, y, Color.Red); else sceneRenderer.SetPixel(x, y, Color.Black); } } } SetPixel simply sets a value in a single dimensional array of colours. If I call the function normally by just directly calling it it runs at a constant 55fps. If I do: Thread t1 = new Thread(() => Trace(0, 1, testSphere)); t1.Start(); t1.Join(); It runs at a constant 50fps which is fine and understandable, but when I do: Thread t1 = new Thread(() => Trace(0, 2, testSphere)); Thread t2 = new Thread(() => Trace(1, 2, testSphere)); t1.Start(); t2.Start(); t1.Join(); t2.Join(); It runs all over the place, rapidly moving between 30-40 fps and sometimes going out of that range up to 50 or down to 20, it's not constant at all. Why is it running slower than it would if I ran the whole thing on a single thread? I'm running on a quad core i5 2500k.

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• How `is_base_of` works?

  - by Alexey Malistov

  Why the following code works? typedef char (&yes)[1]; typedef char (&no)[2]; template <typename B, typename D> struct Host { operator B*() const; operator D*(); }; template <typename B, typename D> struct is_base_of { template <typename T> static yes check(D*, T); static no check(B*, int); static const bool value = sizeof(check(Host<B,D>(), int())) == sizeof(yes); }; //Test sample class Base {}; class Derived : private Base {}; //Exspression is true. int test[is_base_of<Base,Derived>::value && !is_base_of<Derived,Base>::value]; Note that B is private base. Note that operator B*() is const. How does this work? Why this works? Why static yes check(D*, T); is better than static yes check(B*, int); ?

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• How do interpreters functions written in the class C++ in the main

  - by T_Geek

  Hi I'm working on a project about Data structures. In the first , I wrote everything in main but it sounds like C . But as I learned, I tried to thinkk OOP and do as little as possible in my main() methods. I've implemented some opertation in my class like add,delet,find.it's too easy to implement its . class ARB { private: struct BT { int data; BT *l; BT *r; }; struct BT *p; public ARB(); ~ARB(); void del(int n); void add(int n); }; void ARB::del(int num) { //The code ,don't care about it }; main() { // BTR T; T.add(3); T.add(5); }; But I arrived to the big program How can I define a methode which have to use a binary tree and to get a stack STACK ARB::MyFunct(BT* p) { // The code don't care about it } How can I apply it in the main programme main() { // BT T; T.add(3); T.add(5); STACK S; BT* p S=T.MyFunct(p); // error C2664 cannot convert parametre 1 }; **mention :I implement STACK class

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• Project euler problem 45

  - by Peter

  Hi, I'm not yet a skilled programmer but I thought this was an interesting problem and I thought I'd give it a go. Triangle, pentagonal, and hexagonal numbers are generated by the following formulae: Triangle T_(n)=n(n+1)/2 1, 3, 6, 10, 15, ... Pentagonal P_(n)=n(3n-1)/2 1, 5, 12, 22, 35, ... Hexagonal H_(n)=n(2n-1) 1, 6, 15, 28, 45, ... It can be verified that T_(285) = P_(165) = H_(143) = 40755. Find the next triangle number that is also pentagonal and hexagonal. Is the task description. I know that Hexagonal numbers are a subset of triangle numbers which means that you only have to find a number where Hn=Pn. But I can't seem to get my code to work. I only know java language which is why I'm having trouble finding a solution on the net womewhere. Anyway hope someone can help. Here's my code public class NextNumber { public NextNumber() { next(); } public void next() { int n = 144; int i = 165; int p = i * (3 * i - 1) / 2; int h = n * (2 * n - 1); while(p!=h) { n++; h = n * (2 * n - 1); if (h == p) { System.out.println("the next triangular number is" + h); } else { while (h > p) { i++; p = i * (3 * i - 1) / 2; } if (h == p) { System.out.println("the next triangular number is" + h); break; } else if (p > h) { System.out.println("bummer"); } } } } } I realize it's probably a very slow and ineffecient code but that doesn't concern me much at this point I only care about finding the next number even if it would take my computer years :) . Peter

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• g++ problem with -l option and PostgreSQL

  - by difek

  Hi I've written simple program. Here a code: #include <iostream> #include <stdio.h> #include <D:\Program Files\PostgreSQL\8.4\include\libpq-fe.h> #include <string> using namespace std; int main() { PGconn *conn; PGresult *res; int rec_count; int row; int col; cout << "ble ble: " << 8 << endl; conn = PQconnectdb("dbname=db_pm host=localhost user=postgres password=postgres"); if (PQstatus(conn) == CONNECTION_BAD) { puts("We were unable to connect to the database"); exit(0); } } I'm trying to connect with PostgreSQL. I compile this code with following command: gcc -I/"d:\Program Files\PostgreSQL\" -L/"d:\Program Files\PostgreSQL\8.4\lib\" -lpq -o firstcpp.o firstcpp.cpp This command is from following site: http://www.mkyong.com/database/how-to-building-postgresql-libpq-programs/ And when I compile it I get following error: /cygnus/cygwin-b20/H-i586-cygwin32/i586-cygwin32/bin/ld: cannot open -lpq: No such file or directory collect2: ld returned 1 exit status Does anyone help me? Difek

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