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producer-consumer using arraydeque working only in breakpoint


producer-consumer using arraydeque working only in breakpoint

By : user2956662
Date : November 22 2020, 10:56 AM
To fix this issue ArrayDeque is not thread safe. You'll have to guard it with a lock (synchronized keyword or read/write lock) in order to access it safely from different threads.
Another option is to use a thread safe deque implementation, preferably a blocking one (e.g. LinkedBlockingDeque), which will also allow you to avoid your busy wait for the queue to become non-empty.
code :


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Producer-Consumer wtih remote message queue as producer and ExecutorService as local consumer

Producer-Consumer wtih remote message queue as producer and ExecutorService as local consumer


By : TFung
Date : March 29 2020, 07:55 AM
like below fixes the issue If you use the ThreadPoolExecutor implementation of the ExecutorService then you'll have access to the information you need that's missing from the ExecutorService (e.g. getActiveCount() and getTaskCount())
Producer/Consumer: One Producer, multiple Consumer, each work on same data

Producer/Consumer: One Producer, multiple Consumer, each work on same data


By : J. Rood
Date : March 29 2020, 07:55 AM
will be helpful for those in need Take a look at Guava's EventBus, a part of Guava's library that deals with in-process PubSub-style communication. It might suit your needs and save you from re-inventing some wheel.
If you are looking for interprocess communication, consider a message queue just like Evgeniy proposed.
Python Consumer-Producer. Producer waits for the consumer to consume

Python Consumer-Producer. Producer waits for the consumer to consume


By : Atrublr Hebtyt
Date : March 29 2020, 07:55 AM
Hope that helps There's a race in your code.
Your producer, fpga, Needs to do the following:
code :
self.condition.acquire()  # Step 1
self.condition.wait()  # Step 2
self.condition.notify()  # Step 4 (step 3 is left out here, but its not important)
self.condition.release() # Step 5
self.condition.acquire() # Step 1
self.condition.notify() # Step 2
self.condition.wait() # This isn't a step! And we're releasing the lock when we do it!
self.condition.release() # Step 4 (no step 3 again, but that's ok)
bbb.condition.acquire()
bbb.condition.wait() # This releases the lock and then blocks, waiting to be notified
fpa.condition.acquire()
fpga.condition.notify()
fpga.condition.wait() # bbb acquires the lock right after this, because it's in wait()
bbb.condition.notify()
bbb.condition.release() # fpga.wait() now completes
fpga.condition.release() # Ok, both threads just called release. Now it's race.
fpga.condition.acquire() # The producer won the race. This is bad.
fpga.condition.notify()
fpga.condition.wait() # Releases the lock and waits
bbb.condition.acquire()
bbb.condition.wait() # No they're both waiting, and you're deadlocked.
C++ STL Producer multiple consumer where producer waits for free consumer before producing next value

C++ STL Producer multiple consumer where producer waits for free consumer before producing next value


By : Stephen
Date : March 29 2020, 07:55 AM
Any of those help My little consumer-producer problem had me stumped for some time. I didn't want an implementation where one producer pushes some data round-robin to the consumers, filling up their queues of data respectively.
code :
template<class T>
struct slotted_data {
  std::size_t I;
  T t;
};
template<class T>
using sink = std::function<void(T)>;
template<class T, std::size_t N>
struct async_slots {
  bool produce( slotted_data<T> data ) {
    if (terminate || data.I>=N) return false;
    {
      auto l = lock();
      if (slots[data.I]) return false;
      slots[data.I] = std::move(data.t);
    }
    cv.notify_one();
    return true;
  }
  // rare use of non-lambda cv.wait in the wild!
  bool consume(sink<slotted_data<T>> f) {
    auto l = lock();
    while(!terminate) {
      for (auto& slot:slots) {
        if (slot) {
          auto r = std::move(*slot);
          slot = std::nullopt;
          f({std::size_t(&slot-slots.data()), std::move(r)}); // invoke in lock
          return true;
        }
      }
      cv.wait(l);
    }
    return false;
  }
  // easier and safer version:
  std::optional<slotted_data<T>> consume() {
    std::optional<slotted_data<T>> r;
    bool worked = consume([&](auto&& data) { r = std::move(data); });
    if (!worked) return {};
    return r;
  }
  void finish() {
      {
        auto l = lock();
        terminate = true;
      }
      cv.notify_all();
  }
private:
  auto lock() { return std::unique_lock<std::mutex>(m); }
  std::mutex m;
  std::condition_variable cv;
  std::array< std::optional<T>, N > slots;
  bool terminate = false;
};
template<class T, std::size_t N>
struct slotted_consumer {
  bool consume( std::size_t I, sink<T> sink ) {
    std::optional<T> data;
    std::condition_variable cv;
    std::mutex m;
    bool worked = slots.produce(
      {
        I,
        [&](auto&& t){
          {
            std::unique_lock<std::mutex> l(m);
            data.emplace(std::move(t));
          }
          cv.notify_one();
        }
      }
    );
    if (!worked) return false;
    std::unique_lock<std::mutex> l(m);
    cv.wait(l, [&]()->bool{
      return (bool)data;
    });
    sink( std::move(*data) );
    return true;
  }
  bool produce( T t ) {
    return slots.consume(
        [&](auto&& f) {
            f.t( std::move(t) );
        }
    );
  }
  void finish() {
      slots.finish();
  }
private:
  async_slots< sink<T>, N > slots;
};
why does producer consumer queue with single producer/consumer doesn't need mutex?

why does producer consumer queue with single producer/consumer doesn't need mutex?


By : S.Avery
Date : March 29 2020, 07:55 AM
it fixes the issue Because such queue will usually be implemented as a circular queue. Producer will be writing to the tail of the queue, while consumer reads from the head. They never access the same memory at the same time.
The idea here is that both consumer and producer can track the position of the tail/head independently.
code :
T data[BUFFER_SIZE];
int producerPtr = 0, consumerPtr = 0;

void putItemIntoBuffer(Item item)
{
     data[producerPtr] = item;
     producerPtr = (producerPtr  + 1) % BUFFER_SIZE;
}

Item removeItemFromBuffer(void)
{
     Item item = data[consumerPtr ];
     consumerPtr = (consumerPtr + 1) % BUFFER_SIZE;
     return item;
}
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