WorkQueue.h

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/*
   For more information, please see: http://software.sci.utah.edu

   The MIT License

   Copyright (c) 2009 Scientific Computing and Imaging Institute,
   University of Utah.

   
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///
///@file   WorkQueue.h
///@brief  Manage assignments of work
///
///@author Steve Parker
///        Department of Computer Science
///        University of Utah
///@date   June 1997
///

#ifndef Core_Thread_WorkQueue_h
#define Core_Thread_WorkQueue_h

#include <Core/Thread/Legacy/AtomicCounter.h>

#include <vector>


#include <Core/Thread/Legacy/share.h>
namespace SCIRun {
    struct WorkQueue_private;
    
/**************************************
 
@class
   WorkQueue
   
KEYWORDS
   Thread, Work
   
@details
   Doles out work assignment to various worker threads.  Simple
   attempts are made at evenly distributing the workload.
   Initially, assignments are relatively large, and will get smaller
   towards the end in an effort to equalize the total effort.
   
****************************************/
    class SCISHARE WorkQueue {
    public:
        //////////
        /// Make an empty work queue with no assignments.
        WorkQueue(const char* name);
        
        //////////
        /// Fill the work queue with the specified total number of work
        /// assignments.  <i>num_threads</i> specifies the approximate
        /// number of threads which will be working from this queue.
        /// The optional <i>granularity</i> specifies the degree to
        /// which the tasks are divided.  A large granularity will
        /// create more assignments with smaller assignments.  A
        /// granularity of zero will recieve a single assignment of
        /// approximately uniform size.  <i>name</i> should be a static
        /// string which describes the primitive for debugging purposes.
        void refill(int totalAssignments, int nthreads,
            int granularity=5);
        
        //////////
        /// Destroy the work queue.  Any unassigned work will be lost.  
        ~WorkQueue();
        
        //////////
        /// Called by each thread to get the next assignment.  If
        /// <i>nextAssignment</i> returns true, the thread has a valid
        /// assignment, and then would be responsible for the work 
        /// from the returned <i>start</i> through <i>end-l</i>.
        /// Assignments can range from 0 to  <i>totalAssignments</i>-1.
        /// When <i>nextAssignment</i> returns false, all work has
        /// been assigned.
        bool nextAssignment(int& start, int& end);
        
    private:
        const char* name_;
        int num_threads_;
        int total_assignments_;
        int granularity_;
        std::vector<int> assignments_;
        AtomicCounter current_assignment_;
        bool dynamic_;
        
        void fill();

        // Cannot copy them
        WorkQueue(const WorkQueue& copy);
        WorkQueue& operator=(const WorkQueue&);
    };
} // End namespace SCIRun

#endif