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Journal of Lee Stripp

vortxGE : Threads

Posted by , 11 March 2013 - - - - - - · 874 views
Threads, C++11, vortxGE
After reading lots of tech papers/blogs on C++11 threads I redesigned the way the engine handles threading.

Developers can now change threads manually per Scene, each pipeline : Move, Optimise are now batch threaded for better performance. after lots of testing this approch seems to work better under heavy load and being scalable its my new method of choice.

Here is some code from the engine that creates threads based on nodes.

void lsNode::MoveThread( lsScene* scn, lsOpenGL* opengl, double delta )
{
#ifdef VORTX_DEBUG_NODES
    cout << "lsNode::MoveThred() ********************************" << endl;
#endif
    
    vector<thread> th;
    lsNode *ptr;
    int threads = 1;
    int tc = 0;
    
    // Threads
    if( scn )
    {
        threads = scn->getThreads();
    } else
    {
        threads = thread::hardware_concurrency() * 2;
    }
    
    // cycle through child and its next nodes
    ptr = getNode_list();
    while( ptr )
    {
        // Add thread
        th.push_back( thread( &lsNode::Move, ptr, scn, opengl, delta ) );
        tc++;
        
        // check our thread count
        if(( tc >= threads )||( ptr->getNext_node() == NULL ))
        {
#ifdef VORTX_DEBUG_NODETHREADS
            // debug
            cout << "lsNode::MoveThread - Thread count : " << tc << endl;
#endif
            // Join and wait
            for( auto &t : th )
            {
                t.join();
            }
            // clean up
            th.clear();
            tc = 0;
        }
        ptr = ptr->getNext_node();
    }
    
    // pass it on
    if( getNode_list() ) getNode_list()->MoveThread( scn, opengl, delta );
    if( getNext_node() ) getNext_node()->MoveThread( scn, opengl, delta );
}




C++11 Threads

Posted by , 07 March 2013 - - - - - - · 1,206 views

I was just brushing up on some C++11 concepts the last few nights (looking for parts of the engine to improve) and noticed quite a few people struggling with threads inside classes, as in using a class object as a thread. Some of the responses were so confusing to say the least.

Also they were struggling with std::cout while threads were running. So here's some example code of these problems all in one. I hope it points someone in the right direction.

Files:
lsThread2.h / .cpp
lsThread.h / .cpp
core.h / .cpp
main.cpp
// file : core.h

#ifndef cppThreads_core_h
#define cppThreads_core_h

#include <iostream>
#include <vector>
#include <thread>
#include <mutex>

using namespace std;

/*! Base class
 Used to start some lsThread objects.
 */
class core
{
public:
    core();
    virtual ~core();
    
    void run();
    void logText( const string& val, int tid  );
    
private:
    int nr_threads;
    mutex m;
};


#endif

// file : core.cpp
​
#include "core.h"
#include "lsThread.h"

core::core()
{
    nr_threads = 10;
}

core::~core()
{
}

void core::run()
{
    cout << "########## Start test ##########" << endl;
    
    vector<thread> th;
    lsThread *mt = new lsThread[nr_threads];
    
    //Launch a group of threads
    for( int i = 0; i < nr_threads; ++i )
    {
        mt[i].setTid( i );
        // Shows how to pass args to the start function in lsThread
        th.push_back( thread( &lsThread::start, mt[i], this, 5 ) );
    }
    
    //Join the threads with the main thread which core is running
    for( auto &t : th )
    {
        t.join();
    }
    
    // delete our array of lsThread objects
    delete [] mt;
    cout << "########## End test ##########" << endl;
}

/*! Logging
 This function is here so its in a common thread for all other threads to call.
 Remember in a real world App you would make a better logger.
 */
void core::logText( const string& val, int tid )
{
    // Lock for output
    m.lock();
    cout << "Thread : " << tid << " - " << val << endl;
    m.unlock();
}




Above: a base class that runs in the main thread.
// file : lsThread.h
​
#ifndef cppThreads_lsThread_h
#define cppThreads_lsThread_h

#include <iostream>
#include <thread>
#include <vector>

class core;

using namespace std;

/*! Thread class
 Nothing special about this class, you could thread any class.
 */
class lsThread
{
public:
    lsThread();
    virtual ~lsThread();
    
    virtual void start( core *c, int val );
    
    void setTid( int val )
    {
        tid = val;
    }
    
private:
    int tid;
    
};


#endif

// File : lsThread.cpp

#include "core.h"
#include "lsThread.h"
#include "lsThread2.h"

lsThread::lsThread()
{
    tid = 0;
}

lsThread::~lsThread()
{
}

void lsThread::start( core *c, int val )
{
    c->logText( "lsThread start", tid );
    
    // Here we create some more threads with a new class, based on the passed value.
    vector<thread> th;
    int nr_threads = val;
    lsThread2 *mt = new lsThread2[nr_threads];
    
    //Launch a group of threads
    for( int i = 0; i < nr_threads; ++i )
    {
        mt[i].setTid( i );
        th.push_back( thread( &lsThread2::start, mt[i], c ) );
    }
    
    // Join the threads with the current thread
    // This could be any of the threads created by the core class.
    for( auto &t : th )
    {
        t.join();
    }
    
    // delete our array of lsThread2 objects.
    delete [] mt;
}




Above: This class show how to launch more threads inside the current thread.
// File : lsThread2.h

#ifndef cppThreads_lsThread2_h
#define cppThreads_lsThread2_h

#include <iostream>
#include <thread>
#include <vector>

class core;

using namespace std;

class lsThread2
{
public:
    lsThread2();
    virtual ~lsThread2();
    
    virtual void start( core *c );
    
    void setTid( int val )
    {
        tid = val;
    }
    
private:
    int tid;
};


#endif

// File : lsThread2.cpp

#include "core.h"
#include "lsThread2.h"


lsThread2::lsThread2()
{
    tid = 0;
}

lsThread2::~lsThread2()
{
}

void lsThread2::start( core *c )
{
    // In this thread we just call the core class logging function
    c->logText( "lsThread2 start", tid );
}




Above: Simple thread that will just output a message to stdout.
// File : main.cpp

#include "core.h"


int main(int argc, const char * argv[])
{
    // Thread demo
    core *c = new core();
    c->run();
    delete c;
    
    return 0;
}


Above: And last but not least the main()

I've kept this example as simple as possible but still trying to show as much as possible. Hope it helps someone.

Cheers
Lee


My Business

Posted by , 06 March 2013 - - - - - - · 849 views

Well I've been away from GameDev.net for what seems like forever. It has been a hard road but I'm up and running with the new business. First App is on the AppStore and I created a Online Shop for my site too.

The plan is to start making some money to fund future Games using my engine, once the engine is done I'll release it free. With any luck this means jobs for others and I get back to coding full time. All this hard work is taking me away from what I love! CODE

www.leestripp.com

Cheers
Lee





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