SimpleReducer.h

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

   
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///
///@file   SimpleReducer.h
///@brief  A barrier with reduction operations
///
///@author Steve Parker
///        Department of Computer Science
///        University of Utah
///@date   June 1997
///

#ifndef Core_Thread_SimpleReducer_h
#define Core_Thread_SimpleReducer_h

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

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

namespace SCIRun {

/**************************************
 
@class
   SimpleReducer
   
KEYWORDS
   Thread
   
@details
   Perform reduction operations over a set of threads.  Reduction
   operations include things like global sums, global min/max, etc.
   In these operations, a local sum (operation) is performed on each
   thread, and these sums are added together.
   
****************************************/
    class SCISHARE SimpleReducer : public Barrier {
    public:
        //////////
        /// Create a <b> SimpleReducer</i>.
        /// At each operation, a barrier wait is performed, and the
        /// operation will be performed to compute the global balue.
        /// <i>name</i> should be a static string which describes
        /// the primitive for debugging purposes.
        SimpleReducer(const char* name);

        //////////
        /// Destroy the SimpleReducer and free associated memory.
        virtual ~SimpleReducer();

        //////////
        /// Performs a global sum over all of the threads.  As soon as each
        /// thread has called sum with their local sum, each thread will
        /// return the same global sum.
        double sum(int myrank, int numThreads, double mysum);

        //////////
        /// Performs a global max over all of the threads.  As soon as each
        /// thread has called max with their local max, each thread will
        /// return the same global max.
        double max(int myrank, int numThreads, double mymax);

        //////////
        /// Performs a global min over all of the threads.  As soon as each
        /// thread has called min with their local max, each thread will
        /// return the same global max.
        double min(int myrank, int numThreads, double mymax);

    private:
        struct data {
        double d_;
        };
        struct joinArray {
        data d_;
        // Assumes 128 bytes in a cache line...
        char filler_[128-sizeof(data)];
        };
        struct pdata {
        int buf_;
        char filler_[128-sizeof(int)];  
        };
        joinArray* join_[2];
        pdata* p_;
        int array_size_;
        void collectiveResize(int proc, int numThreads);

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

#endif