SerialTaskQueue Class Reference

#include <FWCore/Concurrency/interface/SerialTaskQueue.h>

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Detailed Description

Description: Runs only one task from the queue at a time

Usage: A SerialTaskQueue is used to provide thread-safe access to a resource. You create a SerialTaskQueue for the resource. When every you need to perform an operation on the resource, you push a 'task' that does that operation onto the queue. The queue then makes sure to run one and only one task at a time. This guarantees serial access to the resource and therefore thread-safety.

The 'tasks' managed by the SerialTaskQueue are just functor objects who which take no arguments and return no values. The simplest way to create a task is to use a C++11 lambda.

Example: Imagine we have the following data structures.

 std::vector<int> values;
 edm::SerialTaskQueue queue;

On thread 1 we can fill the vector

 for(int i=0; i<1000;++i) {
   queue.pushAndWait( [&values,i]{ values.push_back(i);} );
 }

While on thread 2 we periodically print and stop when the vector is filled

 bool stop = false;
 while(not stop) {
   queue.pushAndWait([&false,&values] {
     if( 0 == (values.size() % 100) ) {
        std::cout <<values.size()<<std::endl;
     }
     if(values.size()>999) {
       stop = true;
     }
   });
 }