OCCT/src/OSD/OSD_Parallel_Threads.cxx

// Created on: 2014-08-19
// Created by: Alexander Zaikin
// Copyright (c) 1996-1999 Matra Datavision
// Copyright (c) 2013-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

// Version of parallel executor used when TBB is not available
#ifndef HAVE_TBB

#include <OSD_Parallel.hxx>

#include <OSD_ThreadPool.hxx>

#include <NCollection_Array1.hxx>
#include <Standard_Mutex.hxx>
#include <OSD_Thread.hxx>

namespace 
{
  //! Class implementing tools for parallel processing 
  //! using threads (when TBB is not available);
  //! it is derived from OSD_Parallel to get access to 
  //! Iterator and FunctorInterface nested types.
  class OSD_Parallel_Threads : public OSD_ThreadPool, public OSD_Parallel
  {
  public:
    //! Auxiliary class which ensures exclusive
    //! access to iterators of processed data pool.
    class Range
    {
    public: //! @name public methods

      //! Constructor
      Range(const OSD_Parallel::UniversalIterator& theBegin,
            const OSD_Parallel::UniversalIterator& theEnd)
      : myBegin(theBegin),
        myEnd(theEnd),
        myIt(theBegin)
      {
      }

      //! Returns const link on the first element.
      inline const OSD_Parallel::UniversalIterator& Begin() const
      {
        return myBegin;
      }

      //! Returns const link on the last element.
      inline const OSD_Parallel::UniversalIterator& End() const
      {
        return myEnd;
      }

      //! Returns first non processed element or end.
      //! Thread-safe method.
      inline OSD_Parallel::UniversalIterator It() const
      {
        Standard_Mutex::Sentry aMutex(myMutex);
        return (myIt != myEnd) ? myIt++ : myEnd;
      }

    private: //! @name private methods

      //! Empty copy constructor
      Range(const Range& theCopy);

      //! Empty copy operator.
      Range& operator=(const Range& theCopy);

    private: //! @name private fields

      const   OSD_Parallel::UniversalIterator&  myBegin; //!< Fisrt element of range.
      const   OSD_Parallel::UniversalIterator&  myEnd;   //!< Last element of range.
      mutable OSD_Parallel::UniversalIterator   myIt;    //!< First non processed element of range.
      mutable Standard_Mutex                 myMutex; //!< Access controller for the first non processed element.
    };

    //! Auxiliary wrapper class for thread function.
    class Task : public JobInterface
    {
    public: //! @name public methods

      //! Constructor.
      Task(const OSD_Parallel::FunctorInterface& thePerformer, Range& theRange)
        : myPerformer(thePerformer),
        myRange(theRange)
      {
      }

      //! Method is executed in the context of thread,
      //! so this method defines the main calculations.
      virtual void Perform (int ) Standard_OVERRIDE
      {
        for (OSD_Parallel::UniversalIterator anIter = myRange.It(); anIter != myRange.End(); anIter = myRange.It())
        {
          myPerformer (anIter);
        }
      }

    private: //! @name private methods

      //! Empty copy constructor.
      Task(const Task& theCopy);

      //! Empty copy operator.
      Task& operator=(const Task& theCopy);

    private: //! @name private fields
      const FunctorInterface& myPerformer; //!< Link on functor
      const Range& myRange; //!< Link on processed data block
    };

    //! Launcher specialization.
    class UniversalLauncher : public Launcher
    {
    public:
      //! Constructor.
      UniversalLauncher (OSD_ThreadPool& thePool, int theMaxThreads = -1)
      : Launcher (thePool, theMaxThreads) {}

      //! Primitive for parallelization of "for" loops.
      void Perform (OSD_Parallel::UniversalIterator& theBegin,
                    OSD_Parallel::UniversalIterator& theEnd,
                    const OSD_Parallel::FunctorInterface& theFunctor)
      {
        Range aData (theBegin, theEnd);
        Task aJob (theFunctor, aData);
        perform (aJob);
      }
    };
  };
}

//=======================================================================
//function : forEach
//purpose  : 
//=======================================================================
void OSD_Parallel::forEach (UniversalIterator& theBegin,
                            UniversalIterator& theEnd,
                            const FunctorInterface& theFunctor,
                            Standard_Integer theNbItems)
{
  const Handle(OSD_ThreadPool)& aThreadPool = OSD_ThreadPool::DefaultPool();
  const Standard_Integer aNbThreads = theNbItems != -1 ? Min (theNbItems, aThreadPool->NbDefaultThreadsToLaunch()) : -1;
  OSD_Parallel_Threads::UniversalLauncher aLauncher (*aThreadPool, aNbThreads);
  aLauncher.Perform (theBegin, theEnd, theFunctor);
}

#endif /* ! HAVE_TBB */