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  • Method sscanf() ambiguous behavior

    - by Carmen Cojocaru
    I am trying to understand how sscanf() works. I ran some examples from this page: http://docs.roxen.com/pike/7.0/tutorial/strings/sscanf.xml and they don't work on my platform. I can't understand why. For instance: "sscanf("4711bar", "%d%s", a, b);" makes the program exit with an error... Here is one of the examples that work: "sscanf("foo", "f%s", a);". Does anybody know why? Do they work on your platforms? Thank you. This is my code: int main(void){ char *b = (char*)malloc(sizeof(char)*100); int a = 0; sscanf("4711bar", "%d%s", a, b); printf("%d", a); printf("%s", b); }

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  • passing different structs to a function in c

    - by clear2k
    I have different structures that need to be filled out the same way. The only difference is that they are filled based on different data. I was wondering if it's possible to pass different structures to a certain function. What I have in mind is something like: struct stu1 { char *a; int b; }; struct stu2 { char *a; int b; }; static struct not_sure **some_func(struct not_sure *not_sure_here, original_content_list) { // do something and return passed struct for(i=0; i<size_of_original_content_list; i++){ //fill out passed structure } return the_struct; } int main(int argc, char *argv[]) { return_struct1 = some_func(stu1); return_struct2 = some_func(stu2); // do something separate with each return struct... } Any comments will be appreciate it.

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  • NSMutableArray of Objects misbehaves ...

    - by iFloh
    I hope someone understands what happens to my NSMutableArray. I read records a, b, c, d from a database, load the fields into an object an add the object to an array. To do this I read the records into an instance of that object (tmpEvent) and add the Object to the target array (NSMutableArray myArray). the code looks like: for (condition) { tmpEvent.field1 = [NSString stringWithUTF8String:(char*)sqlite3_column_text(stmt, 0)]; tmpEvent.field2 = [NSString stringWithUTF8String:(char*)sqlite3_column_text(stmt, 1)]; tmpEvent.field3 = [NSString stringWithUTF8String:(char*)sqlite3_column_text(stmt, 2)]; NSLog(@"myArray: adding %@", tmpEvent.field1); [myArray addObject:tmpEvent]; } The NSLog shows myArray: adding a myArray: adding b myArray: adding c myArray: adding d Subsequent I enumerate the array (this can be in the same or a different method): for (myObject *records in myArray) { NSLog(@"iEvents value %@", records.field1); } The NSLog now shows: myArray value d myArray value d myArray value d myArray value d a mystery .... ??? any thoughts?

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  • seg violation using pycapsule_new

    - by user1733051
    I am trying some simple c API, where I am using PyCapsule_New to encapsulate a pointer. I am running into segment violation, can some body help me. mystruct *func1(int streamno, char mode,unsigned int options) { char * s; s=malloc(100); return s; } PyObject *Wrapper_func1(PyObject *self, PyObject *args) { int streamno; char mode; unsigned int options; mystruct* result; if (!PyArg_ParseTuple(args,"icI",&streamno,&mode,&options)) return NULL; result = func1(streamno,mode,options); return PyCapsule_New( result,NULL,NULL); }

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  • Checking for an "end of line" in a C-string

    - by Numerator
    I would really love your help with the following problem: I want to get as an input from the user a maximum length of 30 chars string and check whether it contains an end of line. This is what I tried to write so far: int main(void) { int i; char* command = (char*)calloc(31, sizeof(char)); while (0 < 1) { scanf("%s", command); for (i = 0; i <= strlen(command); ++i) { if (command[i] == '\n') printf("here"); } if (strcmp(command, "quit") == 0) break; } The idea is to check whether the command given by the user as input is "legal" - that is of length < 31. when i run this code, it never prints "here" regardless of the length of input.

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  • Pointers in C with binary file

    - by darkie15
    Hi All, I am reading the contents of the file using fread into an char array. But I am not sure why it is not getting printed in the output. Here is the code: void getInfo(FILE* inputFile) { char chunk[4]; int liIndex; for (liIndex = 0 ; liIndex < 4 ; liIndex++) { fread(chunk, sizeof(char), 4, inputFile); } printf("\n chunk %s", chunk); } Output prints nothing at all. Where am I going wrong? Regards , darkie

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  • Function to get a string and return same after processing in C

    - by C0de_Hard
    I am working on a code which requires a function. This function gets a string as input and returns a string. What I have planned so far is to get a str[], remove all $'s and spaces, and store this in another string which is returned later: char *getstring(char str[]) { int i=0; char rtn[255]; while (i<strlen(str)) { if (str[i] != " " || str[i] != "$" ) rtn[i] = str[i]; else rtn[i] = ''; } return str; } I dont feel like this will work. Any ideas?? :-S

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  • Is it a good idea to include a large text variable in compiled code?

    - by gladman
    I am writing a program that produces a formatted file for the user, but it's not only producing the formatted file, it does more. I want to distribute a single binary to the end user and when the user runs the program, it will generate the xml file for the user with appropriate data. In order to achieve this, I want to give the file contents to a char array variable that is compiled in code. When the user runs the program, I will write out the char file to generate an xml file for the user. char* buffers = "a xml format file contents, \ this represent many block text \ from a file,..."; I have two questions. Q1. Do you have any other ideas for how to compile my file contents into binary, i.e, distribute as one binary file. Q2. Is this even a good idea as I described above?

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  • adobe air stream end on line (EOF)

    - by goseta
    Hi to all, I need to read a file, which has an "n" number of lines, I need to know when reading the end of each line, so I can store the line in an array, ok so far I have while(stream.position < stream.bytesAvailable) { char = stream.readUTFBytes(1); if(char == "\n") { array.push(line); line = ""; } else { line += char; } } my question is, always the end of line will be "\n"?? how can I be sure if is not an other character like \r??, there is an other character for end of line??, thanks for any help!!!

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  • Hi, i have a c programming doubt? I want to know the difference between the two and where one is use

    - by aks
    Hi, i have a c programming doubt? I want to know the difference between the two and where one is useful over other? suppose i have a struct called employee as below: struct emp{ char first_name[10]; char last_name[10]; char key[10]; }; Now, i want to store the table of employee records, then which method should i use: struct emp e1[100]; // Or struct emp * e1[100]; I know the two are not same but would like to know a use case where second declaration would be of interest and more advantageous to use? Can someone clarify?

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  • C++: How to design a utility class?

    - by Martijn Courteaux
    Hi, The title says it all. But I don't know if I should go for static methods, just a header, a class, or something else? What would be best practice? But, I don't want to have an instance of a utility class. I want to add functions like: Uint32 MapRGB (int r, int g, int b); const char* CopyString(const char* char); // etc. You know: utility methods...

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  • strcat implementation

    - by skydoor
    I tried to implement the strcat by myself, and I found the strcat implementation from Wiki like this......but when I use it, there is segmentation fault. What's from with the code below? char * strcat(char *dest, const char *src) { size_t i,j; for (i = 0; dest[i] != '\0'; i++) ; for (j = 0; src[j] != '\0'; j++) dest[i+j] = src[j]; dest[i+j] = '\0'; return dest; }

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  • how to form an array of numbers , taken input from a file in C

    - by mekasperasky
    The program should be able to make an array of numbers from a text file which reads like this The data is given as this 123 2132 1100909 3213 89890 my code for it is char a; char d[100]; char array[100]; a=fgetc(fp) // where fp is a file pointer if (a=='') { d[count1]='/0'; strcpy(&array[count],d); count=count+1; memset(d,'\0',100) count1=0; } else { d[count1]=a; count1=count1+1; } a=fgetc(fp);

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  • Static referencing error

    - by maxflow
    public class HelloWorld { public static void main(String [] args) { char[] b = {'a', 'b', 'a', 'c'}; int p = 4; deleteRepeats(b, p); } public void deleteRepeats(char[] a, int size) { int currentElement; currentElement = 0; do { for (int i = currentElement; i < size-1; i++) { if (a[currentElement] == a[i+1]) a[i+1] = ' '; } currentElement++; } while (currentElement < size-1); } } I get the error: non-static method deleteRepeats(char[],int) cannot be referenced from a static context deleteRepeats(b,p); Can someone tell me what this means? I tried removing "static" from the main method, but I get the error: Exception in thread "main" java.lang.NoSuchMethodError: main. Thanks in advance

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  • Converting Java code block to Objective-C

    - by user1123688
    I am trying to convert my Android app to iOS. This will be my first iOS app. I can't seem to translate this code properly. If someone wouldn't mind showing me how its done, that would be greatly appreciated. //scrambBase20 is a Byte array String descramble(String input){ char[] ret; ret = input.toCharArray(); int offset = -scrambBase20.length; for(int i=0;i<input.length();i++){ if(i%scrambBase20.length==0) offset+=scrambBase20.length; ret[scrambBase20[i%scrambBase20.length]+offset]=(char) ((byte) (input.charAt(i))^0x45); } String realRet = ""; for (char x : ret){ realRet+=x; } realRet = realRet.trim(); return realRet; }

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  • Do I have to write my own IsNumeric function?

    - by cf_PhillipSenn
    I found this function: function IsNumeric(sText) { var ValidChars = "0123456789."; var IsNumber=true; var Char; for (i = 0; i < sText.length && IsNumber == true; i++) { Char = sText.charAt(i); if (ValidChars.indexOf(Char) == -1){ IsNumber = false; } } return IsNumber; }; Q: Isn't there a built-in JavaScript function for isNumeric? Something like val()?

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  • Pass --nogpgcheck to yum via puppet

    - by quickshiftin
    How would one get a --nogpgcheck option to yum via puppet? I've tried package { 'unsigned-package': ensure => latest, install_options => ['--nogpgcheck'], } and package { 'unsigned-package': ensure => latest, install_options => ['nogpgcheck'], } but looking at the output from an agent run, yum isn't getting that option. As an aside (and maybe the reason it's not working for me), how do I verify my puppet has the install_options feature? I'm running puppet 3.3.0-rc2.

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  • How does versioning work when using Boost Serialization for Derived Classes?

    - by Venkata Adusumilli
    When a Client serializes the following data: InternationalStudent student; student.id("Client ID"); student.firstName("Client First Name"); student.country("Client Country"); the Server receives the following: ID = "Client ID" Country = "Client First Name" instead of the following: ID = "Client ID" Country = "Client Country" The only difference between the Server and Client classes is the First Name of the Student. How can we make the Server ignore First Name recieved from the Client and process the Country? Server Side Classes class Student { public: Student(){} virtual ~Student(){} public: std::string id() { return idM; } void id(std::string id) { idM = id; } protected: friend class boost::serialization::access; protected: std::string idM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(idM); } }; class InternationalStudent : public Student { public: InternationalStudent() {} ~InternationalStudent() {} public: std::string country() { return countryM; } void country(std::string country) { countryM = country; } protected: friend class boost::serialization::access; protected: std::string countryM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(boost::serialization::base_object<Student>(*this)); archive & BOOST_SERIALIZATION_NVP(countryM); } }; Client Side Classes class Student { public: Student(){} virtual ~Student(){} public: std::string id() { return idM; } void id(std::string id) { idM = id; } std::string firstName() { return firstNameM; } void firstName(std::string name) { firstNameM = name; } protected: friend class boost::serialization::access; protected: std::string idM; std::string firstNameM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(idM); if (version >=1) { archive & BOOST_SERIALIZATION_NVP(firstNameM); } } }; BOOST_CLASS_VERSION(Student, 1) class InternationalStudent : public Student { public: InternationalStudent() {} ~InternationalStudent() {} public: std::string country() { return countryM; } void country(std::string country) { countryM = country; } protected: friend class boost::serialization::access; protected: std::string countryM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(boost::serialization::base_object<Student>(*this)); archive & BOOST_SERIALIZATION_NVP(countryM); } };

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  • Polymorphism problem: How to check type of derived class?

    - by malymato
    Hi, this is my first question here :) I know that I should not check for object type but instead use dynamic_cast, but that would not solve my problem. I have class called Extension and interfaces called IExtendable and IInitializable, IUpdatable, ILoadable, IDrawable (the last four are basicly the same). If Extension implements IExtendable interface, it can extend itself with different Extension objects. The problem is that I want to allow the Extension which implements IExtendable to extend only with Extension that implements the same interfaces as the original Extension. You probably don't unerstand that mess so I try to explain it with code: class IExtendable { public: IExtendable(void); void AddExtension(Extension*); void RemoveExtensionByID(unsigned int); vector<Extension*>* GetExtensionPtr(){return &extensions;}; private: vector<Extension*> extensions; }; class IUpdatable { public: IUpdatable(void); ~IUpdatable(void); virtual void Update(); }; class Extension { public: Extension(void); virtual ~Extension(void); void Enable(){enabled=true;}; void Disable(){enabled=false;}; unsigned int GetIndex(){return ID;}; private: bool enabled; unsigned int ID; static unsigned int _indexID; }; Now imagine the case that I create Extension like this: class MyExtension : public Extension, public IExtendable, public IUpdatable, public IDrawable { public: MyExtension(void); virtual ~MyExtension(void); virtual void AddExtension(Extension*); virtual void Update(); virtual void Draw(); }; And I want to allow this class to extend itself only with Extensions that implements the same interfaces (or less). For example I want it to be able to take Extension which implements IUpdatable; or both IUpdatable and IDrawable; but e.g. not Extension which implements ILoadable. I want to do this because when e.g. Update() will be called on some Extension which implements IExtendable and IUpdateable, it will be also called on these Extensions which extends this Extension. So when I'm adding some Extension to Extension which implements IExtendable and some of the IUpdatable, ILoadable... I'm forced to check if Extension that is going to be add implements these interfaces too. So In the IExtendable::AddExtension(Extension*) I would need to do something like this: void IExtendable::AddExtension(Extension* pEx) { bool ok = true; // check wheather this extension can take pEx // do this with every interface if ((*pEx is IUpdatable) && (*this is_not IUpdatable)) ok = false; if (ok) this->extensions.push_back(pEx); } But how? Any ideas what would be the best solution? I don't want to use dynamic_cast and see if it returns null... thanks

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  • MySQL: Creating table with FK error (errno 150)

    - by Peter Bailey
    I've tried searching on this error and nothing I've found helps me, so I apologize in advance if this is a duplicate and I'm just too dumb to find it. I've created a model with MySQL Workbench and am now attempting to install it to a mysql server. Using File Export Forward Engineer SQL CREATE Script... it outputs a nice big file for me, with all the settings I ask for. I switch over to MySQL GUI Tools (the Query Browser specifically) and load up this script (note that I'm going form one official MySQL tool to another). However, when I try to actually execute this file, I get the same error over and over SQLSTATE[HY000]: General error: 1005 Can't create table './srs_dev/location.frm' (errno: 150) "OK", I say to myself, something is wrong with the location table. So I check out the definition in the output file. SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; -- ----------------------------------------------------- -- Table `state` -- ----------------------------------------------------- DROP TABLE IF EXISTS `state` ; CREATE TABLE IF NOT EXISTS `state` ( `state_id` INT NOT NULL AUTO_INCREMENT , `iso_3166_2_code` VARCHAR(2) NOT NULL , `name` VARCHAR(60) NOT NULL , PRIMARY KEY (`state_id`) ) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `brand` -- ----------------------------------------------------- DROP TABLE IF EXISTS `brand` ; CREATE TABLE IF NOT EXISTS `brand` ( `brand_id` INT UNSIGNED NOT NULL AUTO_INCREMENT , `name` VARCHAR(45) NOT NULL , `domain` VARCHAR(45) NOT NULL , `manager_name` VARCHAR(100) NULL , `manager_email` VARCHAR(255) NULL , PRIMARY KEY (`brand_id`) ) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `location` -- ----------------------------------------------------- DROP TABLE IF EXISTS `location` ; CREATE TABLE IF NOT EXISTS `location` ( `location_id` INT UNSIGNED NOT NULL AUTO_INCREMENT , `name` VARCHAR(255) NOT NULL , `address_line_1` VARCHAR(255) NULL , `address_line_2` VARCHAR(255) NULL , `city` VARCHAR(100) NULL , `state_id` TINYINT UNSIGNED NULL DEFAULT NULL , `postal_code` VARCHAR(10) NULL , `phone_number` VARCHAR(20) NULL , `fax_number` VARCHAR(20) NULL , `lat` DECIMAL(9,6) NOT NULL , `lng` DECIMAL(9,6) NOT NULL , `contact_url` VARCHAR(255) NULL , `brand_id` TINYINT UNSIGNED NOT NULL , `summer_hours` VARCHAR(255) NULL , `winter_hours` VARCHAR(255) NULL , `after_hours_emergency` VARCHAR(255) NULL , `image_file_name` VARCHAR(100) NULL , `manager_name` VARCHAR(100) NULL , `manager_email` VARCHAR(255) NULL , `created_date` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , PRIMARY KEY (`location_id`) , CONSTRAINT `fk_location_state` FOREIGN KEY (`state_id` ) REFERENCES `state` (`state_id` ) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `fk_location_brand` FOREIGN KEY (`brand_id` ) REFERENCES `brand` (`brand_id` ) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; CREATE INDEX `fk_location_state` ON `location` (`state_id` ASC) ; CREATE INDEX `fk_location_brand` ON `location` (`brand_id` ASC) ; CREATE INDEX `idx_lat` ON `location` (`lat` ASC) ; CREATE INDEX `idx_lng` ON `location` (`lng` ASC) ; Looks ok to me. I surmise that maybe something is wrong with the Query Browser, so I put this file on the server and try to load it this way ] mysql -u admin -p -D dbname < path/to/create_file.sql And I get the same error. So I start to Google this issue and find all kinds of accounts that talk about an error with InnoDB style tables that fail with foreign keys, and the fix is to add "SET FOREIGN_KEY_CHECKS=0;" to the SQL script. Well, as you can see, that's already part of the file that MySQL Workbench spat out. So, my question is then, why is this not working when I'm doing what I think I'm supposed to be doing? Version Info: # MySQL: 5.0.45 GUI Tools: 1.2.17 Workbench: 5.0.30

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  • C++ MySQL++ Delete query statement brain killer question

    - by shauny
    Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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  • Why is processing a sorted array faster than an unsorted array?

    - by GManNickG
    Here is a piece of code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x: #include <algorithm> #include <ctime> #include <iostream> int main() { // generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! with this, the next loop runs faster std::sort(data, data + arraySize); // test clock_t start = clock(); long long sum = 0; for (unsigned i = 0; i < 100000; ++i) { // primary loop for (unsigned c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC; std::cout << elapsedTime << std::endl; std::cout << "sum = " << sum << std::endl; } Without std::sort(data, data + arraySize);, the code runs in 11.54 seconds. With the sorted data, the code runs in 1.93 seconds. Initially I thought this might be just a language or compiler anomaly. So I tried it Java... import java.util.Arrays; import java.util.Random; public class Main { public static void main(String[] args) { // generate data int arraySize = 32768; int data[] = new int[arraySize]; Random rnd = new Random(0); for (int c = 0; c < arraySize; ++c) data[c] = rnd.nextInt() % 256; // !!! with this, the next loop runs faster Arrays.sort(data); // test long start = System.nanoTime(); long sum = 0; for (int i = 0; i < 100000; ++i) { // primary loop for (int c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } System.out.println((System.nanoTime() - start) / 1000000000.0); System.out.println("sum = " + sum); } } with a similar but less extreme result. My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated. What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.

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  • STL find performs bettern than hand-crafter loop

    - by dusha
    Hello all, I have some question. Given the following C++ code fragment: #include <boost/progress.hpp> #include <vector> #include <algorithm> #include <numeric> #include <iostream> struct incrementor { incrementor() : curr_() {} unsigned int operator()() { return curr_++; } private: unsigned int curr_; }; template<class Vec> char const* value_found(Vec const& v, typename Vec::const_iterator i) { return i==v.end() ? "no" : "yes"; } template<class Vec> typename Vec::const_iterator find1(Vec const& v, typename Vec::value_type val) { return find(v.begin(), v.end(), val); } template<class Vec> typename Vec::const_iterator find2(Vec const& v, typename Vec::value_type val) { for(typename Vec::const_iterator i=v.begin(), end=v.end(); i<end; ++i) if(*i==val) return i; return v.end(); } int main() { using namespace std; typedef vector<unsigned int>::const_iterator iter; vector<unsigned int> vec; vec.reserve(10000000); boost::progress_timer pt; generate_n(back_inserter(vec), vec.capacity(), incrementor()); //added this line, to avoid any doubts, that compiler is able to // guess the data is sorted random_shuffle(vec.begin(), vec.end()); cout << "value generation required: " << pt.elapsed() << endl; double d; pt.restart(); iter found=find1(vec, vec.capacity()); d=pt.elapsed(); cout << "first search required: " << d << endl; cout << "first search found value: " << value_found(vec, found)<< endl; pt.restart(); found=find2(vec, vec.capacity()); d=pt.elapsed(); cout << "second search required: " << d << endl; cout << "second search found value: " << value_found(vec, found)<< endl; return 0; } On my machine (Intel i7, Windows Vista) STL find (call via find1) runs about 10 times faster than the hand-crafted loop (call via find2). I first thought that Visual C++ performs some kind of vectorization (may be I am mistaken here), but as far as I can see assembly does not look the way it uses vectorization. Why is STL loop faster? Hand-crafted loop is identical to the loop from the STL-find body. I was asked to post program's output. Without shuffle: value generation required: 0.078 first search required: 0.008 first search found value: no second search required: 0.098 second search found value: no With shuffle (caching effects): value generation required: 1.454 first search required: 0.009 first search found value: no second search required: 0.044 second search found value: no Many thanks, dusha. P.S. I return the iterator and write out the result (found or not), because I would like to prevent compiler optimization, that it thinks the loop is not required at all. The searched value is obviously not in the vector.

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  • Do I need to manually create indexes for a DBIx::Class belongs_to relationship

    - by Dancrumb
    I'm using the DBIx::Class modules for an ORM approach to an application I have. I'm having some problems with my relationships. I have the following package MySchema::Result::ClusterIP; use strict; use warnings; use base qw/DBIx::Class::Core/; our $VERSION = '1.0'; __PACKAGE__->load_components(qw/InflateColumn::Object::Enum Core/); __PACKAGE__->table('cluster_ip'); __PACKAGE__->add_columns( # Columns here ); __PACKAGE__->set_primary_key('objkey'); __PACKAGE__->belongs_to( 'configuration' => 'MySchema::Result::Configuration', 'config_key'); __PACKAGE__->belongs_to( 'cluster' => 'MySchema::Result::Cluster', { 'foreign.config_key' => 'self.config_key', 'foreign.id' => 'self.cluster_id' } ); As well as package MySchema::Result::Cluster; use strict; use warnings; use base qw/DBIx::Class::Core/; our $VERSION = '1.0'; __PACKAGE__->load_components(qw/InflateColumn::Object::Enum Core/); __PACKAGE__->table('cluster'); __PACKAGE__->add_columns( # Columns here ); __PACKAGE__->set_primary_key('objkey'); __PACKAGE__->belongs_to( 'configuration' => 'MySchema::Result::Configuration', 'config_key'); __PACKAGE__->has_many('cluster_ip' => 'MySchema::Result::ClusterIP', { 'foreign.config_key' => 'self.config_key', 'foreign.cluster_id' => 'self.id' }); There are a couple of other modules, but I don't believe that they are relevant. When I attempt to deploy this schema, I get the following error: DBIx::Class::Schema::deploy(): DBI Exception: DBD::mysql::db do failed: Can't create table 'test.cluster_ip' (errno: 150) [ for Statement "CREATE TABLE `cluster_ip` ( `objkey` smallint(5) unsigned NOT NULL auto_increment, `config_key` smallint(5) unsigned NOT NULL, `cluster_id` char(16) NOT NULL, INDEX `cluster_ip_idx_config_key_cluster_id` (`config_key`, `cluster_id`), INDEX `cluster_ip_idx_config_key` (`config_key`), PRIMARY KEY (`objkey`), CONSTRAINT `cluster_ip_fk_config_key_cluster_id` FOREIGN KEY (`config_key`, `cluster_id`) REFERENCES `cluster` (`config_key`, `id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `cluster_ip_fk_config_key` FOREIGN KEY (`config_key`) REFERENCES `configuration` (`config_key`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB"] at test_deploy.pl line 18 (running "CREATE TABLE `cluster_ip` ( `objkey` smallint(5) unsigned NOT NULL auto_increment, `config_key` smallint(5) unsigned NOT NULL, `cluster_id` char(16) NOT NULL, INDEX `cluster_ip_idx_config_key_cluster_id` (`config_key`, `cluster_id`), INDEX `cluster_ip_idx_config_key` (`config_key`), PRIMARY KEY (`objkey`), CONSTRAINT `cluster_ip_fk_config_key_cluster_id` FOREIGN KEY (`config_key`, `cluster_id`) REFERENC ES `cluster` (`config_key`, `id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `cluster_ip_fk_config_key` FOREIGN KEY (`config_key`) REFERENCES `configuration` (`conf ig_key`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB") at test_deploy.pl line 18 From what I can tell, MySQL is complaining about the FOREIGN KEY constraint, in particular, the REFERENCE to (config_key, id) in the cluster table. From my reading of the MySQL documentation, this seems like a reasonable complaint, especially in regards to the third bullet point on this doc page. Here's my question. Am I missing something in the DBIx::Class module? I realize that I could explicitly create the necessary index to match up with this foreign key constraint, but that seems to be repetitive work. Is there something I should be doing to make this occur implicitly?

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