#include<config.h>
CPS_START_NAMESPACE
/*!\file
  \brief  Definition of the LinkBuffer class.

  $Id $
*/
//--------------------------------------------------------------------
//  CVS keywords
//
//  $Author: zs $
//  $Date: 2004/08/18 11:57:37 $
//  $Header: /space/cvs/cps/cps++/include/util/link_buffer.h,v 1.4 2004/08/18 11:57:37 zs Exp $
//  $Id: link_buffer.h,v 1.4 2004/08/18 11:57:37 zs Exp $
//  $Name: v5_0_16_hantao_io_test_v7 $
//  $Locker:  $
//  $RCSfile: link_buffer.h,v $
//  $Revision: 1.4 $
//  $Source: /space/cvs/cps/cps++/include/util/link_buffer.h,v $
//  $State: Exp $
//
//--------------------------------------------------------------------
#ifndef LINK_BUFFER_H
#define LINK_BUFFER_H                    //!< Prevent multiple inclusion.

CPS_END_NAMESPACE
#include <util/list.h>
CPS_START_NAMESPACE

class Matrix;
class Lattice;
struct LinkEntry;

//-----------------------------------------------------------------
//
//! LinkBuffer is a class that buffers the off-node links. 
// 
//-----------------------------------------------------------------

class LinkBuffer{
  char * cname;
  int site_stride[4];
  int node_stride[4];
  int site_size[4];
  int tab_size;
    //size of the hash table
  int buf_sz;
    //the size of the buffer, used for debuging 

  list_head * hash_tab; 
  //the hash table is indexed by the local coordinates and 
  //the direction of the link. in this way, it would be easy to remove
  //all links with the same local coordinates and orientation. 
  //this is important because when a local link is changed, the same
  //links on other nodes are most likely also changed, if we have the 
  //buffered version of thoses links we should remove them from the buffer. 
  //Note we need to clean up these links when we try to update the
  //corresponding local link, no matter whether it's accepted or not.
  //---------------------------------------------------------------

  list_head flush_list;
  //flush_list defines the order in which the links should be removed,
  //if we run out of memory, that is, if free_list becomes empty.
  //---------------------------------------------------------------
  
  list_head free_list;
  //free_list is the pool of memory for buffering links.
  //---------------------------------------------------------------

  Lattice &lat;
  //reference to the lattice
  
  LinkEntry * link_entry_buf;

  int hash(const int *x, int mu);
  int GetNodeId(const int * x );
  // int check_lists();

 public: 

//! Allocate the link buffer.  
/*!
  Allocates a buffer for \a size links on lattice \a lat
  \param lat The lattice on which the links live.
  \param size The size of this buffer (how many links it can contain).
*/
  LinkBuffer(Lattice & lat, int size); 
	
  ~LinkBuffer();

  //----------------------------------------------------------------
  // GetBufferedLink looks into the buffer to search for the a given 
  // link if it's not there, it gets the link from the neighbours 
  //----------------------------------------------------------------
  //! Gets a link from the buffer.
  Matrix * GetBufferedLink(const int *x, int mu);
  
  //----------------------------------------------------------------
  // ClearBufferedLink looks into the buffer to search for a given link
  // if it's there, remove it from the buffer. 
  // In the heatbath algorithm when a local link is changed we need to make
  // sure that the offnode links in the buffer that has the same
  // local coordiates (in its local coordinates) get removed from 
  // the buffer  
  //----------------------------------------------------------------
  //! Removes links from the buffer.
  void ClearBufferedLink(const int *x, int mu);

  //! Removes all links from the buffer.
  void ClearAll();

};

//Given a coordinate relative to the origin of this node, determine how many G-parity boundaries are crossed to reach it
int nGparityBoundariesCrossed(const int * x);

#endif


CPS_END_NAMESPACE