Lag in the main loop

moisesdias

Hello guys, i'm facing a problem with my program:
I've only write a code for make a circle walk 10 pixels on the screem 60 times per second, but the circle sometimes "jumps", like if it have walked 50 pixels or more instead of 10, I'm going to post my main loop, hope you can help me finding where is the problem

#SelectExpand
  1while(!finish)
  2    {
  3        while(!al_is_event_queue_empty(eventQueue))
  4        {
  5            al_wait_for_event(eventQueue, &event);
  6
  7            if(event.type == ALLEGRO_EVENT_KEY_DOWN)
  8                Keys::keyPressed(keys, event.keyboard.keycode);
  9
 10            if(event.type == ALLEGRO_EVENT_KEY_UP)
 11                Keys::keyReleased(keys, event.keyboard.keycode);
 12
 13            if(event.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
 14                finish = true;
 15
 16            if(event.type == ALLEGRO_EVENT_TIMER)
 17            {
 18                gamePlay.update(keys, finish);
 19                
 20                draw = true;           
 21            }
 22        }
 23        if(draw)
 24        {
 25            draw = false;
 26            gamePlay.drawGame();
 27        }
 28}
 29
 30
 31
 32void GamePlay::update(bool* keys, bool& finish)
 33{
 34    if(posX > 1000)
 35        test = false;
 36    if (posX < 50)
 37        test = true;
 38    if(test)
 39        posX+=10;
 40    else
 41        posX-=10;
 42}
 43
 44
 45
 46void GamePlay::drawGame()
 47{
 48    al_draw_filled_circle(posX,posY,50,al_map_rgba(255,0,0,255));
 49    al_flip_display();
 50    al_clear_to_color(al_map_rgb(0,0,0));/**isso afeta o backbuffer**/
 51}

Elias

Remove the ! before al_is_event_queue_empty(). You want to call al_wait_for_event when the queue is empty and wait until there is an event. The way you have it you would only wait for an event if there already is one, so never... which means your loop just runs through millions of times heating up a CPU core and making everything unstable and jumpy.

moisesdias

Hi Elias, thanks for your reply, I tried to change the main loop but unfortunely my drawings are still jumpy.

I tried a lot of new combinations, but none of them seems to solve the problem

#SelectExpand
  1while(!finish)
  2    {
  3
  4        while(1)
  5        {
  6            al_wait_for_event(eventQueue, &event);
  7
  8            if(event.type == ALLEGRO_EVENT_KEY_DOWN)
  9                Keys::keyPressed(keys, event.keyboard.keycode);
 10
 11            if(event.type == ALLEGRO_EVENT_KEY_UP)
 12                Keys::keyReleased(keys, event.keyboard.keycode);
 13
 14            if(event.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
 15                finish = true;
 16
 17            if(event.type == ALLEGRO_EVENT_TIMER)
 18                gamePlay.update(keys, finish);
 19
 20            if(al_is_event_queue_empty(eventQueue))
 21                gamePlay.drawGame();
 22        }
 23
 24    }

I also tried a logic with two timers, one for the logic and other for drawing, but it have not worked too.

trictonicmp

#SelectExpand
  1//-------------------------------Main loop--------------------------------
  2while (!done)
  3{
  4  do
  5  {
  6  //------------------------Getting events--------------------------
  7    ALLEGRO_EVENT event;
  8    al_wait_for_event(eventQueue, &event);
  9
 10    if (event.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
 11      done = true;
 12
 13
 14
 15    if (event.type == ALLEGRO_EVENT_TIMER)
 16    {
 17      redraw = true;
 18    }
 19    
 20        //-----------------------Getting events END-----------------------
 21  } while (!al_is_event_queue_empty(eventQueue));
 22
 23
 24
 25  //-------------------------Redrawing elements-------------------------
 26    if (redraw)
 27    {
 28      al_flip_display();
 29      redraw = false;
 30    }
 31  //-----------------------Redrawing elements END-----------------------
 32  }
 33//-----------------------------Main loop END------------------------------

I always use this as my main loop, the only thing that I notice is that your code does not have the "ALLEGRO_EVENT event;" before "al_wait_for_event(eventQueue, &event);"

Elias

trictonicmp's loop looks right to me. The key points are:

call al_wait_for_event when there's nothing else to do
only redraw when there was a timer event
only redraw when there are no events left in the queue

roger levy

Good thread. I'm going to try upgrading Ramen's loop using the advice in here.

Edgar Reynaldo

Fixing the formatting and making it more condensed :

#SelectExpand
 bool redraw = true;
 bool quit = false;
  3
 while (!quit) {
    if (redraw) {
       Draw();
       redraw = false;
    }
    do {
       ALLEGRO_EVENT ev;
       al_wait_for_event(q , &ev);
       if (ev.type == ALLEGRO_EVENT_TIMER) {
          Update(dt);
          redraw = true;
       }
       /// Handle events here
    } while (!al_is_event_queue_empty(q));
 }

This is pretty much the standard loop, and has been on the wiki for a while. It's just your basic event loop.

moisesdias

Guys, thanks for all the answers, but i'm beginning to get worried about it.. I have removed all the miscellaneous code and I'm going to put here what i'm compiling, it is only three classes, maybe this way it will be easier to find my problem, if there is one:

it's really strange, it only prints a red ball moving from one side to another, but it still give some 'jumps' at every two seconds approximately

edit: if you guys want, you can run this program only with this code below, i don't discard the possibility of the problem be my installation, and not in my code, who knows..

#SelectExpand
   1//----------the main class----------
   2
   3#include "GameManager.h"
   4int main()
   5{
   6    GameManager US;
   7    return 0;
   8}
   9
  10//----------GameManager header----------
  11
  12#ifndef GAMEMANAGER_H
  13#define GAMEMANAGER_H
  14#include "GamePlay.h"
  15
  16class GameManager
  17{
  18    public:
  19        GameManager();
  20        void manage();
  21
  22    private:
  23        GamePlay gamePlay;
  24
  25        ALLEGRO_DISPLAY* screen;
  26        ALLEGRO_EVENT_QUEUE* eventQueue;
  27        ALLEGRO_TIMER* timer;
  28
  29};
  30
  31#endif // GAMEMANAGER_H
  32
  33
  34//----------GameManager source----------
  35
  36#include "GameManager.h"
  37
  38
  39GameManager::GameManager()
  40{
  41
  42    draw = true;
  43    finish = false;
  44    screen = NULL;
  45    eventQueue = NULL;
  46    timer = NULL;
  47
  48    if(!al_init())
  49        finish = true;
  50
  51    screen = al_create_display(1200,800);
  52
  53    if(!screen || !al_init_primitives_addon())
  54        finish = true;
  55
  56    timer = al_create_timer(1.0 / 60);
  57
  58    eventQueue = al_create_event_queue();
  59
  60    al_register_event_source(eventQueue, al_get_timer_event_source(timer));
  61    al_register_event_source(eventQueue, al_get_display_event_source(screen));
  62
  63    al_start_timer(timer);
  64
  65    manage();
  66}
  67
  68
  69
  70void GameManager::manage()
  71{
  72    bool draw = true;
  73    bool finish = false;
  74
  75    while (!finish)
  76    {
  77        if (draw)
  78        {
  79            gamePlay.drawGame();
  80            draw = false;
  81        }
  82        do
  83        {
  84            ALLEGRO_EVENT ev;
  85            al_wait_for_event(eventQueue, &ev);
  86            if (ev.type == ALLEGRO_EVENT_TIMER)
  87            {
  88                gamePlay.update();
  89                draw = true;
  90            }
  91
  92            // i have also tried to put the gamePlay.updat() here
  93        }
  94        while (!al_is_event_queue_empty(eventQueue));
  95    }
  96}
  97
  98
  99
 100//----------GamePlay header----------
 101
 102#ifndef GAMEPLAY_H
 103#define GAMEPLAY_H
 104
 105#include <allegro5/allegro.h>
 106#include <allegro5/allegro_primitives.h>
 107class GamePlay
 108{
 109    public:
 110        GamePlay();
 111        void update();
 112        void drawGame();
 113
 114    private:
 115        int posX;
 116        int posY;
 117        bool test;
 118};
 119
 120#endif // GAMEPLAY_H
 121
 122
 123//----------GamePlay source----------
 124
 125#include "GamePlay.h"
 126
 127GamePlay::GamePlay()
 128{
 129    posX = 500;
 130    posY = 500;
 131    test = false;
 132}
 133void GamePlay::update()
 134{
 135    if(posX > 1000)
 136        test = false;
 137    if (posX < 50)
 138        test = true;
 139    if(test)
 140        posX+=10;
 141    else
 142        posX-=10;
 143}
 144void GamePlay::drawGame()
 145{
 146    al_draw_filled_circle(posX,posY,50,al_map_rgba(255,0,0,255));
 147    al_flip_display();
 148    al_clear_to_color(al_map_rgb(0,0,0));
 149}

Edgar Reynaldo

If you're going to provide code, provide something that compiles please.

Here's your code fixed up and compiling :

#SelectExpand
   1//----------the main class----------
   2
   3
   4//----------GamePlay header----------
   5
   6#ifndef GAMEPLAY_H
   7#define GAMEPLAY_H
   8
   9#include <allegro5/allegro.h>
  10#include <allegro5/allegro_primitives.h>
  11class GamePlay
  12{
  13    public:
  14        GamePlay();
  15        void update();
  16        void drawGame();
  17
  18    private:
  19        int posX;
  20        int posY;
  21        bool test;
  22};
  23
  24#endif // GAMEPLAY_H
  25
  26
  27//#include "GameManager.h"
  28
  29//----------GameManager header----------
  30
  31#ifndef GAMEMANAGER_H
  32#define GAMEMANAGER_H
  33//#include "GamePlay.h"
  34
  35class GameManager
  36{
  37    public:
  38        GameManager();
  39        void manage();
  40
  41    private:
  42        GamePlay gamePlay;
  43
  44        ALLEGRO_DISPLAY* screen;
  45        ALLEGRO_EVENT_QUEUE* eventQueue;
  46        ALLEGRO_TIMER* timer;
  47
  48        bool draw;
  49        bool finish;
  50};
  51
  52#endif // GAMEMANAGER_H
  53
  54
  55//----------GameManager source----------
  56
  57//#include "GameManager.h"
  58
  59
  60GameManager::GameManager()
  61{
  62
  63    draw = true;
  64    finish = false;
  65    screen = NULL;
  66    eventQueue = NULL;
  67    timer = NULL;
  68
  69    if(!al_init())
  70        finish = true;
  71
  72   if (!al_install_keyboard()) {finish = true;}
  73        
  74    screen = al_create_display(1200,800);
  75
  76    if(!screen || !al_init_primitives_addon())
  77        finish = true;
  78
  79    timer = al_create_timer(1.0 / 60);
  80
  81    eventQueue = al_create_event_queue();
  82
  83    al_register_event_source(eventQueue, al_get_timer_event_source(timer));
  84    al_register_event_source(eventQueue, al_get_display_event_source(screen));
  85    al_register_event_source(eventQueue, al_get_keyboard_event_source());
  86
  87    al_start_timer(timer);
  88
  89    manage();
  90}
  91
  92
  93
  94void GameManager::manage()
  95{
  96
  97    while (!finish)
  98    {
  99        if (draw)
 100        {
 101            gamePlay.drawGame();
 102            draw = false;
 103        }
 104        do
 105        {
 106            ALLEGRO_EVENT ev;
 107            al_wait_for_event(eventQueue, &ev);
 108            if (ev.type == ALLEGRO_EVENT_TIMER)
 109            {
 110                gamePlay.update();
 111                draw = true;
 112            }
 113            else if (ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
 114               finish = true;
 115            }
 116            else if (ev.type == ALLEGRO_EVENT_KEY_DOWN && ev.keyboard.keycode == ALLEGRO_KEY_ESCAPE) {
 117               finish = true;
 118            }
 119
 120            // i have also tried to put the gamePlay.updat() here
 121        }
 122        while (!al_is_event_queue_empty(eventQueue));
 123    }
 124}
 125
 126
 127//----------GamePlay source----------
 128
 129//#include "GamePlay.h"
 130
 131GamePlay::GamePlay()
 132{
 133    posX = 500;
 134    posY = 500;
 135    test = false;
 136}
 137void GamePlay::update()
 138{
 139    if(posX > 1000)
 140        test = false;
 141    if (posX < 50)
 142        test = true;
 143    if(test)
 144        posX+=10;
 145    else
 146        posX-=10;
 147}
 148void GamePlay::drawGame()
 149{
 150    al_draw_filled_circle(posX,posY,50,al_map_rgba(255,0,0,255));
 151    al_flip_display();
 152    al_clear_to_color(al_map_rgb(0,0,0));
 153}
 154
 155int main()
 156{
 157    GameManager US;
 158    return 0;
 159}

The resulting exe works fine. The red ball goes back and forth smoothly. There was one glitch on the first run, where it skipped a little, but I assume that was a vsync timing issue.

moisesdias

I'm sorry Edgar, I have removed a lot of classes, I did not see the remaining variables.

So, I don't think that the problem is my computer, maybe I have messed up when installing codeblocks and allegro, but I'm less worried now that it worked fine for you.

do you guys know a recognized tutorial for installation of allegro with any IDE? for windows or linux?

Edgar Reynaldo

I wouldn't consider it solved yet.

The code listed works fine when graphics takes less than 1.0/FPS, but when it takes longer than that, you will have frame skipping. The solution is to discard all timer events after the first in each iteration.

This will skip all extra timer events in case they pile up, and it will slow down gracefully.

#SelectExpand
 bool redraw = true;
 bool quit = false;
  3
 int ticks = 0;
 while (!quit) {
    if (redraw) {
       Draw();
       redraw = false;
       ticks = 0;
    }
    do {
       ALLEGRO_EVENT ev;
       al_wait_for_event(q , &ev);
       if (ev.type == ALLEGRO_EVENT_TIMER) {
          ++ticks;
          if (ticks == 1) {
             Update(dt);
          }
          redraw = true;
       }
       /// Handle events here
    } while (!al_is_event_queue_empty(q));
 }

moisesdias

Edgar, I've tried to put this new variable to avoid updating twice before drawing, but my problem persists, unfortunnely..

I have also tried to leave only the al_flip_display() on my Draw function:

#SelectExpand
  1
  2void GamePlay::update()
  3{
  4    if(posX > 1000)
  5        test = false;
  6    if (posX < 50)
  7        test = true;
  8    if(test)
  9        posX+=10;
 10    else
 11        posX-=10;
 12
 13    al_clear_to_color(al_map_rgb(0,0,0));
 14    al_draw_filled_circle(posX,posY,50,al_map_rgba(255,0,0,255));
 15}
 16void GamePlay::drawGame()
 17{
 18    al_flip_display();
 19
 20}
 21
 22
 23//instead of 
 24
 25
 26
 27void GamePlay::update()
 28{
 29    if(posX > 1000)
 30        test = false;
 31    if (posX < 50)
 32        test = true;
 33    if(test)
 34        posX+=10;
 35    else
 36        posX-=10;
 37}
 38void GamePlay::drawGame()
 39{
 40    al_draw_filled_circle(posX,posY,50,al_map_rgba(255,0,0,255));
 41    al_flip_display();
 42    al_clear_to_color(al_map_rgb(0,0,0));
 43}

but it did not help. Damn, I was pretty sure that the ticks variable would solve the issue hahahaha

edit: I've checked my screen refresh rate and it's on 60Hz

Edgar Reynaldo

moisesdias said:

do you guys know a recognized tutorial for installation of allegro with any IDE? for windows or linux?

MSVS is pretty easy. All you do is use Nugat to install Allegro. MinGW and CodeBlocks is not super hard either, but takes some work. Linux can be as easy as 'sudo apt-get install liballegro5-dev' if you're on Ubuntu.

moisesdias said:

but it did not help. Damn, I was pretty sure that the ticks variable would solve the issue hahahaha

edit: I've checked my screen refresh rate and it's on 60Hz

It literally has to move 10 pixels at a time, there's something else going on.

Did you compile and run the code I gave back to you?

moisesdias

Guys, I've found the problem, it was not the code, but an old VGA monitor that I was using with my notebook, I don't know exactly why, but when I disconnect him the circle moves smoothly on the screen

Anyway, thanks Edgar and thanks for all who have replied!!

Thread #617583. Printed from Allegro.cc