CaloPrefetch.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
 
/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef CALOEVENT_CALOPREFETCH_H
#define CALOEVENT_CALOPREFETCH_H
//--------------------------------------------------------------------------
// File and Version Information:
//  $Id$
//------------------------------------------------------------------------
 
#include "CxxUtils/prefetch.h"
#include "CaloEvent/CaloCell.h"
#include "AthAllocators/ArenaHandle.h"
#include <cstddef>
 
//      ---------------------
//      -- Class Interface --
//      ---------------------

 
namespace CaloPrefetch {
 

template <typename Iter>
inline
void nextDDE(Iter iter, Iter endIter)
{
  if (++iter != endIter) {
    // Get DDE, cell itself is expected to be in the cache already
    CxxUtils::prefetchObj((*iter)->caloDDE());
    if (++iter != endIter) {
      // prefetch cell two steps ahead
      CxxUtils::prefetchObj<CaloCell>(*iter);
    }
  }
}

template <typename Iter>
inline
void nextDDE(Iter iter, Iter endIter, int count)
{
  for (int i = 0; i != count; ++ i) {
    if (++iter != endIter) {
      // Get DDE, cell itself is expected to be in the cache already
      CxxUtils::prefetchObj((*iter)->caloDDE());
    } else {
      return;
    }
  }
  for (int i = 0; i != count; ++ i) {
    if (++iter != endIter) {
      // prefetch cell two steps ahead
      CxxUtils::prefetchObj<CaloCell>(*iter);
    } else {
      return;
    }
  }
}

template <class T, class ALLOC, int COUNT=1>
class ArenaHandlePrefetch : public SG::ArenaHandle<T, ALLOC>{
 
  typedef SG::ArenaHandle<T, ALLOC> Base;
 
public:

  ArenaHandlePrefetch() : Base()
  {
    for (int i = 0; i != COUNT; ++ i) {
      m_buf[i] = Base::allocate();
    }
    for (int i = 0; i != COUNT; ++ i) {
      CxxUtils::prefetchN<sizeof(T)>(m_buf[i]);
    }
  }

  void* allocate()
  {
    void* res = m_buf[0];
    std::move(m_buf + 1, m_buf + COUNT, m_buf);
    m_buf[COUNT-1] = Base::allocate();
    CxxUtils::prefetchN<sizeof(T)>(m_buf[COUNT-1]);
    return res;
  }

  void erase() {
    Base::erase();
    for (int i = 0; i != COUNT; ++ i) {
      m_buf[i] = Base::allocate();
    }
    for (int i = 0; i != COUNT; ++ i) {
      CxxUtils::prefetchN<sizeof(T)>(m_buf[i]);
    }
  }
 
private:
  void* m_buf[COUNT];
};
 
} // namespace CaloPrefetch
 
 
#endif // CALOEVENT_CALOPREFETCH_H