我写了一个用条件变量乘以生产者和消费者的代码。即使当我只有一个生产者和一个消费者时,它也不起作用。生产者和消费者都应在while(true)中运行。当我运行代码时,它阻塞了大约50%的运行。我想它会因等待过多而陷入僵局。我无法成功调试卡住的位置以及如何解锁conds。根据要求,我必须创建带有等待,信号和广播的代码。
如果队列已满,则生产者正在等待。如果队列为空,则消费者正在等待。
void WaitableQueue::enqueue(size_t a_item)
{
(m_cond.getMutex()).lock();
while(m_itemsCounter==m_capacity && !m_isBeingDestroyed)
{
++m_numberOfWaiting;
m_cond.wait();
--m_numberOfWaiting;
}
std::cout<<"enqueue "<<a_item<<"\n";
m_queue.push(a_item);
++m_itemsCounter;
++m_numbOfProduced;
if(m_isBeingDestroyed)
{
m_cond.broadcast();
}
(m_cond.getMutex()).unlock();
m_cond.broadcast();
}
void WaitableQueue::dequeue()
{
(m_cond.getMutex()).lock();
while(m_itemsCounter==0 && !m_isBeingDestroyed)
{
++m_numberOfWaiting;
std::cout<<"Waiting\n";
m_cond.wait();
std::cout<<"Done waiting\n";
--m_numberOfWaiting;
}
if (m_isBeingDestroyed)
{
(m_cond.getMutex()).unlock();
m_cond.broadcast();
return;
}
std::cout<<"dequeue "<<m_queue.front()<<"\n";
m_queue.pop();
--m_itemsCounter;
++m_numbOfConsumed;
(m_cond.getMutex()).unlock();
m_cond.broadcast();
}
void WaitableQueue::destroy()
{
(m_cond.getMutex()).lock();
m_isBeingDestroyed=true;
(m_cond.getMutex()).unlock();
}
void Producer::run()
{
for(size_t i=0;i<m_numOfItemsToProduce;++i)
{
usleep(m_delay);
size_t item=produce();
m_wq.enqueue(item);
}
}
Producer::produce() const
{
return rand()%m_numOfItemsToProduce;
}
void Consumer::run()
{
m_numOfProducersMutex.lock();
while(m_numOfProducers>0)
{
m_numOfProducersMutex.unlock();
usleep(m_delay);
m_wq.dequeue();
m_numOfProducersMutex.lock();
}
m_numOfProducersMutex.unlock();
}
int main()
{
size_t numProducers=1;
size_t numConsumers=3;
Mutex mutex;
ConditionalVariable cond(mutex);
WaitableQueue<size_t> wq(NUM_OF_ITEMS,cond);
std::vector<Producer<size_t>*> producerArray;
std::vector<Consumer<size_t>*> consumerArray;
Mutex numOfProducersMutex;
for(size_t i=0;i<numProducers;++i)
{
Producer<size_t>* tempP=new Producer<size_t>(wq,NUM_OF_ITEMS,DELAY);
producerArray.push_back(tempP);
}
for(size_t i=0;i<numConsumers;++i)
{
Consumer<size_t>* tempC=new Consumer<size_t>(wq,numProducers,numOfProducersMutex,DELAY);
consumerArray.push_back(tempC);
}
for(size_t i=0;i<numProducers;++i)
{
producerArray[i]->start();
}
for(size_t i=0;i<numConsumers;++i)
{
consumerArray[i]->start();
}
for(size_t i=0;i<numProducers;++i)
{
producerArray[i]->join();
numOfProducersMutex.lock();
--numProducers;
numOfProducersMutex.unlock();
}
usleep(100);
//tell the consumers stop waiting
wq.destroy();
for(size_t i=0;i<numConsumers;++i)
{
consumerArray[i]->join();
}
for(size_t i=0;i<numProducers;++i)
{
delete producerArray[i];
}
for(size_t i=0;i<numConsumers;++i)
{
delete consumerArray[i];
}
}
它运行约50%。另外50%的用户则被卡住。
要使用条件变量解决生产者-消费者问题,首先需要了解有界缓冲区问题。
您已经找到了C ++如何从概念上简单的问题中解决难题的另一个示例。