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• Can someone code review my small SDL app? Want to make sure I didn't make any beginner mistakes

  - by SDLFunTimes

  In an effort to teach myself the SDL library (hence my stack overflow handle :) ) I wanted to try my hand at a side-scroller. My code is complete but I want some feedback (mostly because I have an atrocious amount of if and else statements for what seems like some simple logic). My "program" is a c++ side-scroller where you move a single sprite across the screen. No jumping, bad guys, guns, scores, levels or anything. I wanted to use this as a base to build up upon. So I figured if my base is wrong I could end up with some pretty bad future apps. It's also multi-threaded. Next up on this I would like to make the person sprite animated (so it looks like he's walking rather than sliding) as well as make the person go faster when the arrow buttons are held down longer). The code is kind of long but here's my main method. There's a link at the bottom for the whole program: #include <iostream> #include "SDL.h" #include "game.hpp" using std::cout; using std::endl; const int SCREENW = 200; const int SCREENH = 200; const int BPP = 32; const int FPS = 24; int event_loop(void* stuff); int display_loop(void* stuff); int main(int argc, char** argv) { SDL_Init(SDL_INIT_EVERYTHING | SDL_INIT_EVENTTHREAD); SDL_Thread* events_thurd; SDL_Thread* display_thurd; SDL_Surface* screen = SDL_SetVideoMode(SCREENW, SCREENH, BPP, SDL_SWSURFACE); SDL_EnableKeyRepeat(SDL_DEFAULT_REPEAT_DELAY, SDL_DEFAULT_REPEAT_INTERVAL); SDL_Event event; Game* thug_aim = new Game(&event, screen, SCREENW, SCREENH, BPP); events_thurd = SDL_CreateThread(event_loop, (void*)thug_aim); display_thurd = SDL_CreateThread(display_loop, (void*)thug_aim); SDL_WaitThread(events_thurd, NULL); SDL_KillThread(display_thurd); delete thug_aim; return 0; } int event_loop(void* stuff) { Game* gamez = (Game*)stuff; SDL_Event* event = gamez->get_event(); while(1) { while(SDL_PollEvent(event)) { if(event->type == SDL_QUIT) { return 0; } else if(event->type == SDL_KEYDOWN) { if(event->key.keysym.sym == SDLK_LEFT || event->key.keysym.sym == SDLK_RIGHT) { gamez->move(event->key.keysym.sym); } } else if(event->type == SDL_KEYUP) { if(event->key.keysym.sym == SDLK_LEFT || event->key.keysym.sym == SDLK_RIGHT) { gamez->stop_move(event->key.keysym.sym); } } else { //not an event that concerns this game } } } } int display_loop(void* stuff) { Game* gamez = (Game*)stuff; double period = 1 / FPS * 1000; Uint32 milli_period = (Uint32)period; //get some of the attributes from gamez SDL_Rect* background_rect = gamez->get_background_rect(); SDL_Rect* person_rect = gamez->get_person_rect(); SDL_Surface* screen = gamez->get_screen(); SDL_Surface* background = gamez->get_background(); SDL_Surface* person = gamez->get_person(); Uint32 start, end; int sleep; while(1) { start = SDL_GetTicks(); //blit background SDL_BlitSurface(background, background_rect, screen, NULL); //blit person SDL_BlitSurface(person, NULL, screen, person_rect); end = SDL_GetTicks(); sleep = milli_period - (end - start); if(sleep < 0) { sleep = 0; } SDL_Delay((Uint32)sleep); if(SDL_Flip(gamez->get_screen()) != 0) { cout << "error drawing to screen: " << SDL_GetError() << endl; } } } Here's the link to the .zip file of all my code (please ignore some of the variable names ;-) ): Anyway can you guys take a look and tell me what you think? url edit: holy crap I didn't know 2shared was such a shitty site. Looking for a better uploader than that or rapidshare / mediafire.

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• Policy-based template design: How to access certain policies of the class?

  - by dehmann

  I have a class that uses several policies that are templated. It is called Dish in the following example. I store many of these Dishes in a vector (using a pointer to simple base class), but then I'd like to extract and use them. But I don't know their exact types. Here is the code; it's a bit long, but really simple: #include <iostream> #include <vector> struct DishBase { int id; DishBase(int i) : id(i) {} }; std::ostream& operator<<(std::ostream& out, const DishBase& d) { out << d.id; return out; } // Policy-based class: template<class Appetizer, class Main, class Dessert> class Dish : public DishBase { Appetizer appetizer_; Main main_; Dessert dessert_; public: Dish(int id) : DishBase(id) {} const Appetizer& get_appetizer() { return appetizer_; } const Main& get_main() { return main_; } const Dessert& get_dessert() { return dessert_; } }; struct Storage { typedef DishBase* value_type; typedef std::vector<value_type> Container; typedef Container::const_iterator const_iterator; Container container; Storage() { container.push_back(new Dish<int,double,float>(0)); container.push_back(new Dish<double,int,double>(1)); container.push_back(new Dish<int,int,int>(2)); } ~Storage() { // delete objects } const_iterator begin() { return container.begin(); } const_iterator end() { return container.end(); } }; int main() { Storage s; for(Storage::const_iterator it = s.begin(); it != s.end(); ++it){ std::cout << **it << std::endl; std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? } return 0; } The tricky part is here, in the main() function: std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? How can I access the dessert? I don't even know the Dessert type (it is templated), let alone the complete type of the object that I'm getting from the storage. This is just a toy example, but I think my code reduces to this. I'd just like to pass those Dish classes around, and different parts of the code will access different parts of it (in the example: its appetizer, main dish, or dessert).

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• MySQL query, 2 similar servers, 2 minute difference in execution times

  - by mr12086

  I had a similar question on stack overflow, but it seems to be more server/mysql setup related than coding. The queries below all execute instantly on our development server where as they can take upto 2 minutes 20 seconds. The query execution time seems to be affected by home ambiguous the LIKE string's are. If they closely match a country that has few matches it will take less time, and if you use something like 'ge' for germany - it will take longer to execute. But this doesn't always work out like that, at times its quite erratic. Sending data appears to be the culprit but why and what does that mean. Also memory on production looks to be quite low (free memory)? Production: Intel Quad Xeon E3-1220 3.1GHz 4GB DDR3 2x 1TB SATA in RAID1 Network speed 100Mb Ubuntu Development Intel Core i3-2100, 2C/4T, 3.10GHz 500 GB SATA - No RAID 4GB DDR3 UPDATE 2 : mysqltuner output: [prod] -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.61-0ubuntu0.10.04.1 [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 103M (Tables: 180) [--] Data in InnoDB tables: 491M (Tables: 19) [!!] Total fragmented tables: 38 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 77d 4h 6m 1s (53M q [7.968 qps], 14M conn, TX: 87B, RX: 12B) [--] Reads / Writes: 98% / 2% [--] Total buffers: 58.0M global + 2.7M per thread (151 max threads) [OK] Maximum possible memory usage: 463.8M (11% of installed RAM) [OK] Slow queries: 0% (12K/53M) [OK] Highest usage of available connections: 22% (34/151) [OK] Key buffer size / total MyISAM indexes: 16.0M/10.6M [OK] Key buffer hit rate: 98.7% (162M cached / 2M reads) [OK] Query cache efficiency: 20.7% (7M cached / 36M selects) [!!] Query cache prunes per day: 3934 [OK] Sorts requiring temporary tables: 1% (3K temp sorts / 230K sorts) [!!] Joins performed without indexes: 71068 [OK] Temporary tables created on disk: 24% (3M on disk / 13M total) [OK] Thread cache hit rate: 99% (690 created / 14M connections) [!!] Table cache hit rate: 0% (64 open / 85M opened) [OK] Open file limit used: 12% (128/1K) [OK] Table locks acquired immediately: 99% (16M immediate / 16M locks) [!!] InnoDB data size / buffer pool: 491.9M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Adjust your join queries to always utilize indexes Increase table_cache gradually to avoid file descriptor limits Variables to adjust: query_cache_size (> 16M) join_buffer_size (> 128.0K, or always use indexes with joins) table_cache (> 64) innodb_buffer_pool_size (>= 491M) [dev] -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.62-0ubuntu0.11.10.1 [!!] Switch to 64-bit OS - MySQL cannot currently use all of your RAM -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 185M (Tables: 632) [--] Data in InnoDB tables: 967M (Tables: 38) [!!] Total fragmented tables: 73 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 1d 2h 26m 9s (5K q [0.058 qps], 1K conn, TX: 4M, RX: 1M) [--] Reads / Writes: 99% / 1% [--] Total buffers: 58.0M global + 2.7M per thread (151 max threads) [OK] Maximum possible memory usage: 463.8M (11% of installed RAM) [OK] Slow queries: 0% (0/5K) [OK] Highest usage of available connections: 1% (2/151) [OK] Key buffer size / total MyISAM indexes: 16.0M/18.6M [OK] Key buffer hit rate: 99.9% (60K cached / 36 reads) [OK] Query cache efficiency: 44.5% (1K cached / 2K selects) [OK] Query cache prunes per day: 0 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 44 sorts) [OK] Temporary tables created on disk: 24% (162 on disk / 666 total) [OK] Thread cache hit rate: 99% (2 created / 1K connections) [!!] Table cache hit rate: 1% (64 open / 4K opened) [OK] Open file limit used: 8% (88/1K) [OK] Table locks acquired immediately: 100% (1K immediate / 1K locks) [!!] InnoDB data size / buffer pool: 967.7M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Increase table_cache gradually to avoid file descriptor limits Variables to adjust: table_cache (> 64) innodb_buffer_pool_size (>= 967M) UPDATE 1: When testing the queries listed here there is usually no more than one other query taking place, and usually none. Because production is actually handling apache requests that development gets very few of as it's only myself and 1 other who accesses it - could the 4GB of RAM be getting exhausted by using the single machine for both apache and mysql server? Production: sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 24872 MB in 2.00 seconds = 12450.72 MB/sec Timing buffered disk reads: 368 MB in 3.00 seconds = 122.49 MB/sec sudo hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 24786 MB in 2.00 seconds = 12407.22 MB/sec Timing buffered disk reads: 350 MB in 3.00 seconds = 116.53 MB/sec Server version(mysql + ubuntu versions): 5.1.61-0ubuntu0.10.04.1 Development: sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 10632 MB in 2.00 seconds = 5319.40 MB/sec Timing buffered disk reads: 400 MB in 3.01 seconds = 132.85 MB/sec Server version(mysql + ubuntu versions): 5.1.62-0ubuntu0.11.10.1 ORIGINAL DATA : This query is NOT the query in question but is related so ill post it. SELECT f.form_question_has_answer_id FROM form_question_has_answer f INNER JOIN project_company_has_user p ON f.form_question_has_answer_user_id = p.project_company_has_user_user_id INNER JOIN company c ON p.project_company_has_user_company_id = c.company_id INNER JOIN project p2 ON p.project_company_has_user_project_id = p2.project_id INNER JOIN user u ON p.project_company_has_user_user_id = u.user_id INNER JOIN form f2 ON p.project_company_has_user_project_id = f2.form_project_id WHERE (f2.form_template_name = 'custom' AND p.project_company_has_user_garbage_collection = 0 AND p.project_company_has_user_project_id = '29') AND (LCASE(c.company_country) LIKE '%ge%' OR LCASE(c.company_country) LIKE '%abcde%') AND f.form_question_has_answer_form_id = '174' And the explain plan for the above query is, run on both dev and production produce the same plan. +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ | 1 | SIMPLE | p2 | const | PRIMARY | PRIMARY | 4 | const | 1 | Using index | | 1 | SIMPLE | f | ref | form_question_has_answer_form_id,form_question_has_answer_user_id | form_question_has_answer_form_id | 4 | const | 796 | Using where | | 1 | SIMPLE | u | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using index | | 1 | SIMPLE | p | ref | project_company_has_user_unique_key,project_company_has_user_user_id,project_company_has_user_company_id,project_company_has_user_project_id | project_company_has_user_user_id | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using where | | 1 | SIMPLE | f2 | ref | form_project_id | form_project_id | 4 | const | 15 | Using where | | 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_company_id | 1 | Using where | +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ This query takes 2 minutes ~20 seconds to execute. The query that is ACTUALLY being run on the server is this one: SELECT COUNT(*) AS num_results FROM (SELECT f.form_question_has_answer_id FROM form_question_has_answer f INNER JOIN project_company_has_user p ON f.form_question_has_answer_user_id = p.project_company_has_user_user_id INNER JOIN company c ON p.project_company_has_user_company_id = c.company_id INNER JOIN project p2 ON p.project_company_has_user_project_id = p2.project_id INNER JOIN user u ON p.project_company_has_user_user_id = u.user_id INNER JOIN form f2 ON p.project_company_has_user_project_id = f2.form_project_id WHERE (f2.form_template_name = 'custom' AND p.project_company_has_user_garbage_collection = 0 AND p.project_company_has_user_project_id = '29') AND (LCASE(c.company_country) LIKE '%ge%' OR LCASE(c.company_country) LIKE '%abcde%') AND f.form_question_has_answer_form_id = '174' GROUP BY f.form_question_has_answer_id;) dctrn_count_query; With explain plans (again same on dev and production): +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ | 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Select tables optimized away | | 2 | DERIVED | p2 | const | PRIMARY | PRIMARY | 4 | | 1 | Using index | | 2 | DERIVED | f | ref | form_question_has_answer_form_id,form_question_has_answer_user_id | form_question_has_answer_form_id | 4 | | 797 | Using where | | 2 | DERIVED | p | ref | project_company_has_user_unique_key,project_company_has_user_user_id,project_company_has_user_company_id,project_company_has_user_project_id,project_company_has_user_garbage_collection | project_company_has_user_user_id | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using where | | 2 | DERIVED | f2 | ref | form_project_id | form_project_id | 4 | | 15 | Using where | | 2 | DERIVED | c | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_company_id | 1 | Using where | | 2 | DERIVED | u | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_user_id | 1 | Using where; Using index | +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ On the production server the information I have is as follows. Upon execution: +-------------+ | num_results | +-------------+ | 3 | +-------------+ 1 row in set (2 min 14.28 sec) Show profile: +--------------------------------+------------+ | Status | Duration | +--------------------------------+------------+ | starting | 0.000016 | | checking query cache for query | 0.000057 | | Opening tables | 0.004388 | | System lock | 0.000003 | | Table lock | 0.000036 | | init | 0.000030 | | optimizing | 0.000016 | | statistics | 0.000111 | | preparing | 0.000022 | | executing | 0.000004 | | Sorting result | 0.000002 | | Sending data | 136.213836 | | end | 0.000007 | | query end | 0.000002 | | freeing items | 0.004273 | | storing result in query cache | 0.000010 | | logging slow query | 0.000001 | | logging slow query | 0.000002 | | cleaning up | 0.000002 | +--------------------------------+------------+ On development the results are as follows. +-------------+ | num_results | +-------------+ | 3 | +-------------+ 1 row in set (0.08 sec) Again the profile for this query: +--------------------------------+----------+ | Status | Duration | +--------------------------------+----------+ | starting | 0.000022 | | checking query cache for query | 0.000148 | | Opening tables | 0.000025 | | System lock | 0.000008 | | Table lock | 0.000101 | | optimizing | 0.000035 | | statistics | 0.001019 | | preparing | 0.000047 | | executing | 0.000008 | | Sorting result | 0.000005 | | Sending data | 0.086565 | | init | 0.000015 | | optimizing | 0.000006 | | executing | 0.000020 | | end | 0.000004 | | query end | 0.000004 | | freeing items | 0.000028 | | storing result in query cache | 0.000005 | | removing tmp table | 0.000008 | | closing tables | 0.000008 | | logging slow query | 0.000002 | | cleaning up | 0.000005 | +--------------------------------+----------+ If i remove user and/or project innerjoins the query is reduced to 30s. Last bit of information I have: Mysqlserver and Apache are on the same box, there is only one box for production. Production output from top: before & after. top - 15:43:25 up 78 days, 12:11, 4 users, load average: 1.42, 0.99, 0.78 Tasks: 162 total, 2 running, 160 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 50.4%sy, 0.0%ni, 49.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3772580k used, 265288k free, 243704k buffers Swap: 3905528k total, 265384k used, 3640144k free, 1207944k cached top - 15:44:31 up 78 days, 12:13, 4 users, load average: 1.94, 1.23, 0.87 Tasks: 160 total, 2 running, 157 sleeping, 0 stopped, 1 zombie Cpu(s): 0.2%us, 50.6%sy, 0.0%ni, 49.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3834300k used, 203568k free, 243736k buffers Swap: 3905528k total, 265384k used, 3640144k free, 1207804k cached But this isn't a good representation of production's normal status so here is a grab of it from today outside of executing the queries. top - 11:04:58 up 79 days, 7:33, 4 users, load average: 0.39, 0.58, 0.76 Tasks: 156 total, 1 running, 155 sleeping, 0 stopped, 0 zombie Cpu(s): 3.3%us, 2.8%sy, 0.0%ni, 93.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3676136k used, 361732k free, 271480k buffers Swap: 3905528k total, 268736k used, 3636792k free, 1063432k cached Development: This one doesn't change during or after. top - 15:47:07 up 110 days, 22:11, 7 users, load average: 0.17, 0.07, 0.06 Tasks: 210 total, 2 running, 208 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4111972k total, 1821100k used, 2290872k free, 238860k buffers Swap: 4183036k total, 66472k used, 4116564k free, 921072k cached

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• Why is the this-pointer needed to access inherited attributes?

  - by Shadow

  Hi, assume the following class is given: class Base{ public: Base() {} Base( const Base& b) : base_attr(b.base_attr) {} void someBaseFunction() { .... } protected: SomeType base_attr; }; When I want a class to inherit from this one and include a new attribute for the derived class, I would write: class Derived: public Base { public: Derived() {} Derived( const Derived& d ) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void SomeDerivedFunction() { .... } private: SomeOtherType derived_attr; }; This works for me (let's ignore eventually missing semicolons or such please). However, when I remove the "this-" in the copy constructor of the derived class, the compiler complains that "'base_attr' was not declared in this scope". I thought that, when inheriting from a class, the protected attributes would then also be accessible directly. I did not know that the "this-" pointer was needed. I am now confused if it is actually correct what I am doing there, especially the copy-constructor of the Derived-class. Because each Derived object is supposed to have a base_attr and a derived_attr and they obviously need to be initialized/set correctly. And because Derived is inheriting from Base, I don't want to explicitly include an attribute named "base_attr" in the Derived-class. IMHO doing so would generally destroy the idea behind inheritance, as everything would have to be defined again. EDIT Thank you all for the quick answers. I completely forgot the fact that the classes actually are templates. Please, see the new examples below, which are actually compiling when including "this-" and are failing when omiting "this-" in the copy-constructor of the Derived-class: Base-class: #include <iostream> template<class T> class Base{ public: Base() : base_attr(0) {} Base( const Base& b) : base_attr(b.base_attr) {} void baseIncrement() { ++base_attr; } void printAttr() { std::cout << "Base Attribute: " << base_attr << std::endl; } protected: T base_attr; }; Derived-class: #include "base.hpp" template< class T > class Derived: public Base<T>{ public: Derived() : derived_attr(1) {} Derived( const Derived& d) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void derivedIncrement() { ++derived_attr; } protected: T derived_attr; }; and for completeness also the main function: #include "derived.hpp" int main() { Derived<int> d; d.printAttr(); d.baseIncrement(); d.printAttr(); Derived<int> d2(d); d2.printAttr(); return 0; }; I am using g++-4.3.4. Although I understood now that it seems to come from the fact that I use template-class definitions, I did not quite understand what is causing the problem when using templates and why it works when not using templates. Could someone please further clarify this?

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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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• Odd C++ template behaviour with static member vars

  - by jon hanson

  This piece of code is supposed to calculate an approximation to e (i.e. the mathematical constant ~ 2.71828183) at compile-time, using the following approach; e1 = 2 / 1 e2 = (2 * 2 + 1) / (2 * 1) = 5 / 2 = 2.5 e3 = (3 * 5 + 1) / (3 * 2) = 16 / 6 ~ 2.67 e4 = (4 * 16 + 1) / (4 * 6) = 65 / 24 ~ 2.708 ... e(i) = (e(i-1).numer * i + 1) / (e(i-1).denom * i) The computation is returned via the result static member however, after 2 iterations it yields zero instead of the expected value. I've added a static member function f() to compute the same value and that doesn't exhibit the same problem. #include <iostream> #include <iomanip> // Recursive case. template<int ITERS, int NUMERATOR = 2, int DENOMINATOR = 1, int I = 2> struct CalcE { static const double result; static double f () {return CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::f ();} }; template<int ITERS, int NUMERATOR, int DENOMINATOR, int I> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, I>::result = CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::result; // Base case. template<int ITERS, int NUMERATOR, int DENOMINATOR> struct CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS> { static const double result; static double f () {return result;} }; template<int ITERS, int NUMERATOR, int DENOMINATOR> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS>::result = static_cast<double>(NUMERATOR) / DENOMINATOR; // Test it. int main (int argc, char* argv[]) { std::cout << std::setprecision (8); std::cout << "e2 ~ " << CalcE<2>::result << std::endl; std::cout << "e3 ~ " << CalcE<3>::result << std::endl; std::cout << "e4 ~ " << CalcE<4>::result << std::endl; std::cout << "e5 ~ " << CalcE<5>::result << std::endl; std::cout << std::endl; std::cout << "e2 ~ " << CalcE<2>::f () << std::endl; std::cout << "e3 ~ " << CalcE<3>::f () << std::endl; std::cout << "e4 ~ " << CalcE<4>::f () << std::endl; std::cout << "e5 ~ " << CalcE<5>::f () << std::endl; return 0; } I've tested this with VS 2008 and VS 2010, and get the same results in each case: e2 ~ 2 e3 ~ 2.5 e4 ~ 0 e5 ~ 0 e2 ~ 2 e3 ~ 2.5 e4 ~ 2.6666667 e5 ~ 2.7083333 Why does result not yield the expected values whereas f() does? According to Rotsor's comment below, this does work with GCC, so I guess the question is, am i relying on some type of undefined behaviour with regards to static initialisation order, or is this a bug with Visual Studio?

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• C++ Greatest Number Verification

  - by Daniel

  Hey guys, I was assigned to create a program that creates n arrays composed by 10 random integers. The the program should sum all the integers and display the result. After, it has to verify which of the sums is the greatest and it has to display that array and the result. Im having troubles getting it done and would like to get some help! Thanks once again. Here is my code so far: #include <iostream> #include <iomanip> #include <cmath> using namespace std; double random(unsigned int &seed); unsigned int seed = 5; void generateData(int set[10]); int sumData(int set[10]); void checkData(int sumResult, int arrayNumber); int main (int argc, char * const argv[]) { int arrayNumber, sumResult; int set[10]; do { cout << "Number of Arrays to Compare: " << endl; cin >> arrayNumber; } while (arrayNumber < 0); for (int i = 0; i < arrayNumber; ++i) { generateData(set); sumResult = sumData(set); cout << "Sum --> " << sumResult << endl; checkData(sumResult, arrayNumber); } return 0; } double random(unsigned int &seed) { const int MODULUS = 15749; const int MULTIPLIER = 69069; const int INCREMENT = 1; seed = ((MULTIPLIER * seed) + INCREMENT) % MODULUS; return double(seed) / double(MODULUS); } void generateData(int set[10]) { for (int i = 0; i < 10; ++i) { set[i] = int (5 + 6 * random(seed)); cout << set[i] << " || "; } } int sumData(int set[10]) { int sumTotal = 0; for (int i = 0; i < 10; ++i) sumTotal = sumTotal + set[i]; return sumTotal; } void checkData(int sumResult, int arrayNumber) { int largerNumber; int tempSet[2]; for (int i = 0; i < arrayNumber; ++i) { if (sumResult > largerNumber) { tempSet[i] = sumResult; } } }

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• where is the error in this C code , and how to get rid of the warnings?

  - by mekasperasky

  #include<stdio.h> #include<string.h> //This program is a sorting application that reads a sequence of numbers from a file and prints them on the screen . The reading from the file here , is a call back function . typedef int (*CompFunc)(const char* , const char* ); typedef int (*ReadCheck)(char nullcheck); char array[100]; //Let this fucntion be done in the library itself . It doesnt care as to where the compare function and how is it implemented . Meaning suppose the function wants to do sort in ascending order or in descending order then the changes have to be done by the client code in the "COMPARE" function who will be implementing the lib code . void ReadFile(FILE *fp,ReadCheck rc) { char a; char d[100]; int count = 0,count1=0; a=fgetc(fp); while(1 != (*rc)(a)) { if(a=='\0') { strcpy(array[count],d); count=count+1; } else { d[count1]=a; count1=count1+1; } } } void Bubblesort(int* array , int size , int elem_size , CompFunc cf) { int i,j; int *temp; for( i=0;i < size ;i++) { for ( j=0;j < size -1 ; j++) { // make the callback to the comparision function if(1 == (*cf)(array+j*elem_size,array+ (j+1)*elem_size)) { //interchanging of elements temp = malloc(sizeof(int *) * elem_size); memcpy(temp , array+j*elem_size,elem_size); memcpy(array+j*elem_size,array+(j+1)*elem_size,elem_size); memcpy(array + (j+1)*elem_size , temp , elem_size); free(temp); } } } } //Let these functions be done at the client side int Compare(const char* el1 , const char* el2) { int element1 = *(int*)el1; int element2 = *(int*)el2; if(element1 < element2 ) return -1; if(element1 > element2) return 1 ; return 0; } int ReadChecked(char nullcheck) { if (nullcheck=='\n') return 1; else return 0; } int main() { FILE fp1; int k; fp1=fopen("readdata.txt","r"); Readfile(fp1,&ReadChecked); Bubblesort((char*)array,5,sizeof(array[0]),&Compare); printf("after sorting \n"); for (k=0;k<5;k++) printf("%d",array[k]); return 0; } The error i get is fsc1.c: In function ‘ReadFile’: fsc1.c:19: warning: passing argument 1 of ‘strcpy’ makes pointer from integer without a cast fsc1.c: In function ‘Bubblesort’: fsc1.c:40: warning: passing argument 1 of ‘cf’ from incompatible pointer type fsc1.c:40: warning: passing argument 2 of ‘cf’ from incompatible pointer type fsc1.c:43: warning: incompatible implicit declaration of built-in function ‘malloc’ fsc1.c:47: warning: incompatible implicit declaration of built-in function ‘free’ fsc1.c: In function ‘main’: fsc1.c:80: error: incompatible types in assignment fsc1.c:82: warning: passing argument 1 of ‘Bubblesort’ from incompatible pointer type

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• Cocos2d-x v3 invalid conversion from 'cocos2d::Layer* [on hold]

  - by Hammerh5

  Hello guys I'm learning cocos2d-x v3 right but most of the code that I can find is to the version 2. My specific error is this one, when I try to compile my cocos2s-x 3 project this error shows. invalid conversion from 'cocos2d::Layer to Game* [-fpermisive]* What I want to do is create a new game scene in the following code: //Game.cpp #include "Game.h" Scene* Game::scene() { scene *sc = CCScene::create(); sc->setTag(TAG_GAME_SCENE); const Game *g = Game::create(); //Here is where the conversions fails. sc->addChild(g, 0, TAG_GAME_LAYER); return sc; } Of course this is my header file //Game.h #include "cocos2d.h" #include "Mole.h" #include "AppDelegate.h" using namespace cocos2d; class Game: public cocos2d::Layer { cocos2d::CCArray *moles; float timeBetweenMoles, timeElapsed, increaseMolesAtTime, increaseElapsed, lastMoleHiTime; int molesAtOnce; cocos2d::CCSize s; bool isPaused; public: CCString *missSound, *hitSound; static cocos2d::Scene* scene(); virtual bool init(); void showMole(); void initializeGame(); void onEnterTransitionDidFinish(); void onExit(); void onTouchesBegan(const std::vector<cocos2d::Touch *> &touches, cocos2d::Event *event); void tick(float dt); cocos2d::CCArray* getMoles(bool isUp); //LAYER_CREATE_FUNC(Game); }; #endif /* GAME_H_ */ I don't know what's wrong I suppose this code works fine in Cocos2d-x v2. It's maybe some changes in the C++ version ?

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• Achieving forward compatibility with C++11

  - by mcmcc

  I work on a large software application that must run on several platforms. Some of these platforms support some features of C++11 (e.g. MSVS 2010) and some don't support any (e.g. GCC 4.3.x). I see this situation continuing on for several years (my best guess: 3-5 years). Given that, I would like set up a compatibility interface such that (to whatever degree possible) people can write C++11 code that will still compile with older compilers with a minimum of maintenance. Overall, the goal is to minimize #ifdef's as much as reasonably possible while still enabling basic C++11 syntax/features on the platforms that support them, and provide emulation on the platforms that don't. Let's start with std::move(). The most obvious way to achieve compatibility would be to put something like this in a common header file: #if !defined(HAS_STD_MOVE) namespace std { // C++11 emulation template <typename T> inline T& move(T& v) { return v; } template <typename T> inline const T& move(const T& v) { return v; } } #endif // !defined(HAS_STD_MOVE) This allow people to write things like std::vector<Thing> x = std::move(y); ... with impugnity. It does what they want in C++11 and it does the best it can in C++03. When we finally drop the last of the C++03 compilers, this code can remain as is. However, according to the standard, it is illegal to inject new symbols into the std namespace. That's the theory. My question is, practically speaking, is there any harm in doing this as a way of achieving forward compatibility?

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• Android device - C++ OpenGL 2: eglCreateWindowSurface invalid

  - by ThreaderSlash

  I am trying to debug and run OGLES on Native C++ in my Android device in order to implement a native 3D game for mobile smart phones. The point is that I got an error and see no reason for that. Here is the line from the code that the debugger complains: mSurface = eglCreateWindowSurface(mDisplay, lConfig, mApplication->window, NULL); And this is the error message: Invalid arguments ' Candidates are: void * eglCreateWindowSurface(void *, void *, unsigned long int, const int *) ' --x-- Here is the declaration: android_app* mApplication; EGLDisplay mDisplay; EGLint lFormat, lNumConfigs, lErrorResult; EGLConfig lConfig; // Defines display requirements. 16bits mode here. const EGLint lAttributes[] = { EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT, EGL_BLUE_SIZE, 5, EGL_GREEN_SIZE, 6, EGL_RED_SIZE, 5, EGL_SURFACE_TYPE, EGL_WINDOW_BIT, EGL_RENDER_BUFFER, EGL_BACK_BUFFER, EGL_NONE }; // Retrieves a display connection and initializes it. packt_Log_debug("Connecting to the display."); mDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY); if (mDisplay == EGL_NO_DISPLAY) goto ERROR; if (!eglInitialize(mDisplay, NULL, NULL)) goto ERROR; // Selects the first OpenGL configuration found. packt_Log_debug("Selecting a display config."); if(!eglChooseConfig(mDisplay, lAttributes, &lConfig, 1, &lNumConfigs) || (lNumConfigs <= 0)) goto ERROR; // Reconfigures the Android window with the EGL format. packt_Log_debug("Configuring window format."); if (!eglGetConfigAttrib(mDisplay, lConfig, EGL_NATIVE_VISUAL_ID, &lFormat)) goto ERROR; ANativeWindow_setBuffersGeometry(mApplication->window, 0, 0, lFormat); // Creates the display surface. packt_Log_debug("Initializing the display."); mSurface = eglCreateWindowSurface(mDisplay, lConfig, mApplication->window, NULL); --x-- Hope someone here can shed some light on it.

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• glm quaternion camera rotating on wrong axis

  - by Jarrett

  I'm trying to get my camera implemented with a glm::quat used to store the rotation. However, whenever I do circles with the mouse, the camera rotates along the axis I am viewing (i.e. I think it's called the target axis). For example, if I rotated the mouse in a clockwise fashion, the camera rotates clockwise around the axis. I initialize my quaternion like so: void Camera::initialize() { orientationQuaternion_ = glm::quat(); orientationQuaternion_ = glm::normalize(orientationQuaternion_); } I rotate like so: void Camera::rotate(const glm::detail::float32& degrees, const glm::vec3& axis) { orientationQuaternion_ = orientationQuaternion_ * glm::normalize(glm::angleAxis(degrees, axis)); } and I set the viewMatrix like so: void Camera::render() { glm::quat temp = glm::conjugate(orientationQuaternion_); viewMatrix_ = glm::mat4_cast(temp); viewMatrix_ = glm::translate(viewMatrix_, glm::vec3(-pos_.x, -pos_.y, -pos_.z)); } The only axis' I actually try to rotate are the X and Y axis (i.e. (1,0,0) and (0,1,0)). Anyone have any idea why I see my camera rotating around the target axis?

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• Semi Fixed-timestep ported to javascript

  - by abernier

  In Gaffer's "Fix Your Timestep!" article, the author explains how to free your physics' loop from the paint one. Here is the final code, written in C: double t = 0.0; const double dt = 0.01; double currentTime = hires_time_in_seconds(); double accumulator = 0.0; State previous; State current; while ( !quit ) { double newTime = time(); double frameTime = newTime - currentTime; if ( frameTime > 0.25 ) frameTime = 0.25; // note: max frame time to avoid spiral of death currentTime = newTime; accumulator += frameTime; while ( accumulator >= dt ) { previousState = currentState; integrate( currentState, t, dt ); t += dt; accumulator -= dt; } const double alpha = accumulator / dt; State state = currentState*alpha + previousState * ( 1.0 - alpha ); render( state ); } I'm trying to implement this in JavaScript but I'm quite confused about the second while loop... Here is what I have for now (simplified): ... (function animLoop(){ ... while (accumulator >= dt) { // While? In a requestAnimation loop? Maybe if? ... } ... // render requestAnimationFrame(animLoop); // stand for the 1st while loop [OK] }()) As you can see, I'm not sure about the while loop inside the requestAnimation one... I thought replacing it with a if but I'm not sure it will be equivalent... Maybe some can help me.

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• ASP.NET ViewState Tips and Tricks #1

  - by João Angelo

  In User Controls or Custom Controls DO NOT use ViewState to store non public properties. Persisting non public properties in ViewState results in loss of functionality if the Page hosting the controls has ViewState disabled since it can no longer reset values of non public properties on page load. Example: public class ExampleControl : WebControl { private const string PublicViewStateKey = "Example_Public"; private const string NonPublicViewStateKey = "Example_NonPublic"; // DO public int Public { get { object o = this.ViewState[PublicViewStateKey]; if (o == null) return default(int); return (int)o; } set { this.ViewState[PublicViewStateKey] = value; } } // DO NOT private int NonPublic { get { object o = this.ViewState[NonPublicViewStateKey]; if (o == null) return default(int); return (int)o; } set { this.ViewState[NonPublicViewStateKey] = value; } } } // Page with ViewState disabled public partial class ExamplePage : Page { protected override void OnLoad(EventArgs e) { base.OnLoad(e); this.Example.Public = 10; // Restore Public value this.Example.NonPublic = 20; // Compile Error! } }

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• Strange mesh import problem with Assimp and OpenGL

  - by Morgan

  Using the assimp library for importing 3D data into an OpenGL application. I get some strange problems regarding indexing of the vertices: If I use the following code for importing vertex indices: for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } I get the following result: Instead, if I use the following code: for(int k = 0; k < 2 ; k++) { for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } } I get the correct result: Hence adding the indices twice, renders the correct result? The OpenGL buffer is populated, like so: glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices->size() * sizeof(unsigned int), indices->data(), GL_STATIC_DRAW); And rendered as follows: glDrawElements(GL_TRIANGLES, vertexCount*3, GL_UNSIGNED_INT, indices->data());

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• Writing to a D3DFMT_R32F render target clamps to 1

  - by Mike

  I'm currently implementing a picking system. I render some objects in a frame buffer, which has a render target, which has the D3DFMT_R32F format. For each mesh, I set an integer constant evaluator, which is its material index. My shader is simple: I output the position of each vertex, and for each pixel, I cast the material index in float, and assign this value to the Red channel: int ObjectIndex; float4x4 WvpXf : WorldViewProjection< string UIWidget = "None"; >; struct VS_INPUT { float3 Position : POSITION; }; struct VS_OUTPUT { float4 Position : POSITION; }; struct PS_OUTPUT { float4 Color : COLOR0; }; VS_OUTPUT VSMain( const VS_INPUT input ) { VS_OUTPUT output = (VS_OUTPUT)0; output.Position = mul( float4(input.Position, 1), WvpXf ); return output; } PS_OUTPUT PSMain( const VS_OUTPUT input, in float2 vpos : VPOS ) { PS_OUTPUT output = (PS_OUTPUT)0; output.Color.r = float( ObjectIndex ); output.Color.gba = 0.0f; return output; } technique Default { pass P0 { VertexShader = compile vs_3_0 VSMain(); PixelShader = compile ps_3_0 PSMain(); } } The problem I have, is that somehow, the values written in the render target are clamped between 0.0f and 1.0f. I've tried to change the rendertarget format, but I always get clamped values... I don't know what the root of the problem is. For information, I have a depth render target attached to the frame buffer. I disabled the blend in the render state the stencil is disabled Any ideas?

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• Overriding component behavior

  - by deft_code

  I was thinking of how to implement overriding of behaviors in a component based entity system. A concrete example, an entity has a heath component that can be damaged, healed, killed etc. The entity also has an armor component that limits the amount of damage a character receives. Has anyone implemented behaviors like this in a component based system before? How did you do it? If no one has ever done this before why do you think that is. Is there anything particularly wrong headed about overriding component behaviors? Below is rough sketch up of how I imagine it would work. Components in an entity are ordered. Those at the front get a chance to service an interface first. I don't detail how that is done, just assume it uses evil dynamic_casts (it doesn't but the end effect is the same without the need for RTTI). class IHealth { public: float get_health( void ) const = 0; void do_damage( float amount ) = 0; }; class Health : public Component, public IHealth { public: void do_damage( float amount ) { m_damage -= amount; } private: float m_health; }; class Armor : public Component, public IHealth { public: float get_health( void ) const { return next<IHealth>().get_health(); } void do_damage( float amount ) { next<IHealth>().do_damage( amount / 2 ); } }; entity.add( new Health( 100 ) ); entity.add( new Armor() ); assert( entity.get<IHealth>().get_health() == 100 ); entity.get<IHealth>().do_damage( 10 ); assert( entity.get<IHealth>().get_health() == 95 ); Is there anything particularly naive about the way I'm proposing to do this?

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• Understanding math used to determine if vector is clockwise / counterclockwise from your vector

  - by MTLPhil

  I'm reading Programming Game AI by Example by Mat Buckland. In the Math & Physics primer chapter there's a listing of the declaration of a class used to represent 2D vectors. This class contains a method called Sign. It's implementation is as follows //------------------------ Sign ------------------------------------------ // // returns positive if v2 is clockwise of this vector, // minus if anticlockwise (Y axis pointing down, X axis to right) //------------------------------------------------------------------------ enum {clockwise = 1, anticlockwise = -1}; inline int Vector2D::Sign(const Vector2D& v2)const { if (y*v2.x > x*v2.y) { return anticlockwise; } else { return clockwise; } } Can someone explain the vector rules that make this hold true? What do the values of y*v2.x and x*v2.y that are being compared actually represent? I'd like to have a solid understanding of why this works rather than just accepting that it does without figuring it out. I feel like it's something really obvious that I'm just not catching on to. Thanks for your help.

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• How can I ensure my Collada model fits on an iPhone screen?

  - by rakeshNS

  Hi I am new to game development. I see many examples and tried myself like displaying triangle, cube etc. Now I am looking to render a Collada object. So I created a Collada object using Google Sketch up and trying to render that now. But the thing I am not understanding is, in all examples the vertices are between -1.0 and +1.0 values. But when I looked into that Collada file, the vertices were ranging from -30.0 to 90.0. I know any vertices greater than 1.0 will not display on iPhone. So can you pleas tell my the secret behind converting Object coordinate to normalized vector coordinate? My previous triangle defined as struct Vertex{ float Position[3]; float Color[4]; }; const Vertex Vertices[] = { {{-0.5, -0.866}, {1, 1, 0.5f, 1}}, {{0.5, -0.866}, {1, 1, 0.5, 1}}, {{0, 1}, {1, 1, 0.5, 1}}, {{-0.5, -0.866}, {0.5f, 0.5f, 0.5f}}, {{0.5, -0.866}, {0.5f, 0.5f, 0.5f}}, {{0, -0.4f}, {0.5f, 0.5f, 0.5f}}, }; And now triangle from collada is const Vertex Vertices[] = { {{39.4202092, 90.1263924, 0.0000000}, {1, 1, 0.5f, 1}}, {{-20.2205588, 90.1263924, 0.0000000}, {1, 1, 0.5, 1}}, {{-20.2205588, 176.3763924, 0.0000000}, {1, 1, 0.5, 1}}, {{-20.2205588, 176.3763924, 0.0000000}, {1, 1, 0.5, 1}}, {{-20.2205588, 90.1263924, 0.0000000}, {1, 1, 0.5, 1}}, {{39.4202092, 90.1263924, 0.0000000}, {1, 1, 0.5, 1}}, };

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• Learning OpenGL GLSL - VAO buffer problems?

  - by Bleary

  I've just started digging through OpenGL and GLSL, and now stumbled on something I can't get my head around this one!? I've stepped back to loading a simple cube and using a simple shader on it, but the result is triangles drawn incorrectly and/or missing. The code I had working perfectly on meshes, but was attempting to move to using VAOs so none of the code for storing the vertices and indices has changed. http://i.stack.imgur.com/RxxZ5.jpg http://i.stack.imgur.com/zSU50.jpg What I have for creating the VAO and buffers is this //Create the Vertex array object glGenVertexArrays(1, &vaoID); // Finally create our vertex buffer objects glGenBuffers(VBO_COUNT, mVBONames); glBindVertexArray(vaoID); // Save vertex attributes into GPU glBindBuffer(GL_ARRAY_BUFFER, mVBONames[VERTEX_VBO]); // Copy data into the buffer object glBufferData(GL_ARRAY_BUFFER, lPolygonVertexCount*VERTEX_STRIDE*sizeof(GLfloat), lVertices, GL_STATIC_DRAW); glEnableVertexAttribArray(pos); glVertexAttribPointer(pos, 3, GL_FLOAT, GL_FALSE, VERTEX_STRIDE*sizeof(GLfloat),0); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mVBONames[INDEX_VBO]); glBufferData(GL_ELEMENT_ARRAY_BUFFER, lPolygonCount*sizeof(unsigned int), lIndices, GL_STATIC_DRAW); glBindVertexArray(0); And the code for drawing the mesh. glBindVertexArray(vaoID); glUseProgram(shader->programID); GLsizei lOffset = mSubMeshes[pMaterialIndex]->IndexOffset*sizeof(unsigned int); const GLsizei lElementCount = mSubMeshes[pMaterialIndex]->TriangleCount*TRIAGNLE_VERTEX_COUNT; glDrawElements(GL_TRIANGLES, lElementCount, GL_UNSIGNED_SHORT, reinterpret_cast<const GLvoid*>(lOffset)); // All the points are indeed in the correct place!? //glPointSize(10.0f); //glDrawElements(GL_POINTS, lElementCount, GL_UNSIGNED_SHORT, 0); glUseProgram(0); glBindVertexArray(0); Eyes have become bleary looking at this today so any thoughts or a fresh set of eyes would be greatly appreciated.

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• Why is rvalue write in shared memory array serialised?

  - by CJM

  I'm using CUDA 4.0 on a GPU with computing capability 2.1. One of my device functions is the following: device void test(int n, int* itemp) // itemp is shared memory pointer { const int tid = threadIdx.x; const int bdim = blockDim.x; int i, j, k; bool flag = 0; itemp[tid] = 0; for(i=tid; i<n; i+=bdim) { // { code that produces some values of "flag" } } itemp[tid] = flag; } Each thread is checking some conditions and producing a 0/1 flag. Then each thread is writing flag at the tid-th location of a shared int array. The write statement "itemp[tid] = flag;" gets serialized -- though "itemp[tid] = 0;" is not. This is causing huge performance lag which technically should not be there -- I want to avoid it. Please help.

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• CUDA 4.1 Update

  - by N0xus

  I'm currently working on porting a particle system to update on the GPU via the use of CUDA. With CUDA, I've already passed over the required data I need to the GPU and allocated and copied the date via the host. When I build the project, it all runs fine, but when I run it, the project says I need to allocate my h_position pointer. This pointer is my host pointer and is meant to hold the data. I know I need to pass in the current particle position to the required cudaMemcpy call and they are currently stored in a list with a for loop being created and interated for each particle calling the following line of code: m_particleList[i].positionY = m_particleList[i].positionY - (m_particleList[i].velocity * frameTime * 0.001f); My current host side cuda code looks like this: float* h_position; // Your host pointer. This holds the data (I assume it's already filled with the data.) float* d_position; // Your device pointer, we will allocate and fill this float* d_velocity; float* d_time; int threads_per_block = 128; // You should play with this value int blocks = m_maxParticles/threads_per_block + ( (m_maxParticles%threads_per_block)?1:0 ); const int N = 10; size_t size = N * sizeof(float); cudaMalloc( (void**)&d_position, m_maxParticles * sizeof(float) ); cudaMemcpy( d_position, h_position, m_maxParticles * sizeof(float), cudaMemcpyHostToDevice); Both of which were / can be found inside my UpdateParticle() method. I had originally thought it would be a simple case of changing the h_position variable in the cudaMemcpy to m_particleList[i] but then I get the following error: no suitable conversion function from "ParticleSystemClass::ParticleType" to "const void *" exists I've probably messed up somewhere, but could someone please help fix the issues I'm facing. Everything else seems to running fine, it's just when I try to run the program that certain things hit the fan.

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• Storing a pass-by-reference parameter as a pointer - Bad practice?

  - by Karl Nicoll

  I recently came across the following pattern in an API I've been forced to use: class SomeObject { public: // Constructor. SomeObject(bool copy = false); // Set a value. void SetValue(const ComplexType &value); private: bool m_copy; ComplexType *m_pComplexType; ComplexType m_complexType; }; // ------------------------------------------------------------ SomeObject::SomeObject(bool copy) : m_copy(copy) { } // ------------------------------------------------------------ void SomeObject::SetValue(const ComplexType &value) { if (m_copy) m_complexType.assign(value); else m_pComplexType = const_cast<ComplexType *>(&value); } The background behind this pattern is that it is used to hold data prior to it being encoded and sent to a TCP socket. The copy weirdness is designed to make the class SomeObject efficient by only holding a pointer to the object until it needs to be encoded, but also provide the option to copy values if the lifetime of the SomeObject exceeds the lifetime of a ComplexType. However, consider the following: SomeObject SomeFunction() { ComplexType complexTypeInstance(1); // Create an instance of ComplexType. SomeObject encodeHelper; encodeHelper.SetValue(complexTypeInstance); // Okay. return encodeHelper; // Uh oh! complexTypeInstance has been destroyed, and // now encoding will venture into the realm of undefined // behaviour! } I tripped over this because I used the default constructor, and this resulted in messages being encoded as blank (through a fluke of undefined behaviour). It took an absolute age to pinpoint the cause! Anyway, is this a standard pattern for something like this? Are there any advantages to doing it this way vs overloading the SetValue method to accept a pointer that I'm missing? Thanks!

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• Function for building an isosurface (a sphere cut by planes)

  - by GameDevEnthusiast

  I want to build an octree over a quarter of a sphere (for debugging and testing). The octree generator relies on the AIsosurface interface to compute the density and normal at any given point in space. For example, for a full sphere the corresponding code is: // returns <0 if the point is inside the solid virtual float GetDensity( float _x, float _y, float _z ) const override { Float3 P = Float3_Set( _x, _y, _z ); Float3 v = Float3_Subtract( P, m_origin ); float l = Float3_LengthSquared( v ); float d = Float_Sqrt(l) - m_radius; return d; } // estimates the gradient at the given point virtual Float3 GetNormal( float _x, float _y, float _z ) const override { Float3 P = Float3_Set( _x, _y, _z ); float d = this->AIsosurface::GetDensity( P ); float Nx = this->GetDensity( _x + 0.001f, _y, _z ) - d; float Ny = this->GetDensity( _x, _y + 0.001f, _z ) - d; float Nz = this->GetDensity( _x, _y, _z + 0.001f ) - d; Float3 N = Float3_Normalized( Float3_Set( Nx, Ny, Nz ) ); return N; } What is a nice and fast way to compute those values when the shape is bounded by a low number of half-spaces?

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• Capturing Alt+PrintScreen hot key and clipboard contents

  - by kusanagi

  I setup catching hotkey on alt+printscreen. It catches perfectly but there is nothing in the buffer - no image. How can I get the image from Clipboard.GetImage() after catching hotkey? Here is the the code. using System; using System.Runtime.InteropServices; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; namespace Magic_Screenshot { public enum ModifierKey : uint { MOD_NULL = 0x0000, MOD_ALT = 0x0001, MOD_CONTROL = 0x0002, MOD_SHIFT = 0x0004, MOD_WIN = 0x0008, } public enum HotKey { PrintScreen, ALT_PrintScreen, CONTROL_PrintScreen } public class HotKeyHelper : IMessageFilter { const string MSG_REGISTERED = "??????? ??????? ??? ????????????????, ???????? UnRegister ??? ?????? ???????????."; const string MSG_UNREGISTERED = "??????? ??????? ?? ????????????????, ???????? Register ??? ???????????."; //?????? ?? ?????? ?????? singleton public HotKeyHelper() { } //public static readonly HotKeyHelper Instance = new HotKeyHelper(); public bool isRegistered; ushort atom; //ushort atom1; ModifierKey modifiers; Keys keyCode; public void Register(ModifierKey modifiers, Keys keyCode) { //??? ???????? ??? ????? ????? ? PreFilterMessage this.modifiers = modifiers; this.keyCode = keyCode; //?? ????????? ?? ??? ???????????? //if (isRegistered) // throw new InvalidOperationException(MSG_REGISTERED); //????????? atom, ??? ??????????? ?????? ??????????? atom = GlobalAddAtom(Guid.NewGuid().ToString()); //atom1 = GlobalAddAtom(Guid.NewGuid().ToString()); if (atom == 0) ThrowWin32Exception(); if (!RegisterHotKey(IntPtr.Zero, atom, modifiers, keyCode)) ThrowWin32Exception(); //if (!RegisterHotKey(IntPtr.Zero, atom1, ModifierKey.MOD_CONTROL, Keys.PrintScreen)) // ThrowWin32Exception(); //????????? ???? ? ??????? ???????? ????????? Application.AddMessageFilter(this); isRegistered = true; } public void UnRegister() { //?? ???????? ?? ??? ???????????? if (!isRegistered) throw new InvalidOperationException(MSG_UNREGISTERED); if (!UnregisterHotKey(IntPtr.Zero, atom)) ThrowWin32Exception(); GlobalDeleteAtom(atom); //??????? ???? ?? ??????? ???????? ????????? Application.RemoveMessageFilter(this); isRegistered = false; } //?????????? Win32Exception ? ????? ?? ????????? ????? ????????????? Win32 ??????? void ThrowWin32Exception() { throw new Win32Exception(Marshal.GetLastWin32Error()); } //???????, ???????????? ??? ??????????? ??????? HotKeys public event HotKeyHelperDelegate HotKeyPressed; public bool PreFilterMessage(ref Message m) { //???????? ?? ????????? WM_HOTKEY if (m.Msg == WM_HOTKEY && //???????? ?? ???? m.HWnd == IntPtr.Zero && //???????? virtual key code m.LParam.ToInt32() >> 16 == (int)keyCode && //???????? ?????? ????????????? (m.LParam.ToInt32() & 0x0000FFFF) == (int)modifiers && //???????? ?? ??????? ??????????? ????????? HotKeyPressed != null) { if ((m.LParam.ToInt32() & 0x0000FFFF) == (int)ModifierKey.MOD_CONTROL && (m.LParam.ToInt32() >> 16 == (int)Keys.PrintScreen)) { HotKeyPressed(this, EventArgs.Empty, HotKey.CONTROL_PrintScreen); } else if ((m.LParam.ToInt32() & 0x0000FFFF) == (int)ModifierKey.MOD_ALT && (m.LParam.ToInt32() >> 16 == (int)Keys.PrintScreen)) { HotKeyPressed(this, EventArgs.Empty, HotKey.ALT_PrintScreen); } else if (m.LParam.ToInt32() >> 16 == (int)Keys.PrintScreen) { HotKeyPressed(this, EventArgs.Empty, HotKey.PrintScreen); } } return false; } //??????????? Win32 ????????? ? ??????? const string USER32_DLL = "User32.dll"; const string KERNEL32_DLL = "Kernel32.dll"; const int WM_HOTKEY = 0x0312; [DllImport(USER32_DLL, SetLastError = true)] static extern bool RegisterHotKey(IntPtr hWnd, int id, ModifierKey fsModifiers, Keys vk); [DllImport(USER32_DLL, SetLastError = true)] static extern bool UnregisterHotKey(IntPtr hWnd, int id); [DllImport(KERNEL32_DLL, SetLastError = true)] static extern ushort GlobalAddAtom(string lpString); [DllImport(KERNEL32_DLL)] static extern ushort GlobalDeleteAtom(ushort nAtom); } } Where is the bug?

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