anneal.cc 32.8 KB
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/*
 * EMULAB-COPYRIGHT
 * Copyright (c) 2003 University of Utah and the Flux Group.
 * All rights reserved.
 */

#include "anneal.h"

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#include "virtual.h"
#include "maps.h"
#include "common.h"
#include "score.h"
#include "solution.h"
#include "vclass.h"

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/*
 * Internal variables
 */
// These variables store the best solution.
node_map absassignment;		// assignment field of vnode
assigned_map absassigned;	// assigned field of vnode
type_map abstypes;		// type field of vnode

// Map of virtual node name to its vertex descriptor.
name_vvertex_map vname2vertex;

// This is a vector of all the nodes in the top file.  It's used
// to randomly choose nodes.
vvertex_vector virtual_nodes;

// Map of physical node name to its vertex descriptor.
name_pvertex_map pname2vertex;
  
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// Map of virtual node name to the physical node name it's fixed to.
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// The domain is the set of all fixed virtual nodes and the range is
// the set of all fixed physical nodes.
name_name_map fixed_nodes;

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// Map of virtual node name to the physical node name that we should
// start the virtual node on. However, unlike fixed nodes, assign is
// allowed to move these.
name_name_map node_hints;

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// From assign.cc
#ifdef GNUPLOT_OUTPUT
extern FILE *scoresout, *tempout, *deltaout;
#endif

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// Determines whether to accept a change of score difference 'change' at
// temperature 'temperature'.
inline int accept(double change, double temperature)
{
  double p;
  int r;

  if (change == 0) {
    p = 1000 * temperature / temp_prob;
  } else {
    p = expf(change/temperature) * 1000;
  }
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  r = RANDOM() % 1000;
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  if (r < p) {
    return 1;
  }
  return 0;
}

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/*
 * This overly-verbose function returns true if it's okay to map vn to pn,
 * false otherwise
 */
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inline bool pnode_is_match(tb_vnode *vn, tb_pnode *pn) {
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  // Find the type record for this type
  tb_pnode::types_map::iterator mit = pn->types.find(vn->type);
  if (mit == pn->types.end()) {
    // The node doesn't even have this type, we can exit early
    return false;
  }

  bool matched = false;
  tb_pnode::type_record *tr = mit->second;
  if (tr->is_static) {
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    if ((tr->current_load + vn->typecount) > tr->max_load) {
      // This would put us over its max load
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      if (allow_overload && (tr->max_load > 1)) {
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	// That's okay, we're allowing overload
	matched = true;
      } else {
	// Nope, it's full
	matched = false;
      }
    } else {
      // Plenty of room for us
      matched = true;
    }
  } else { // the type is not static
    if (pn->typed) {
      if (pn->current_type.compare(vn->type)) {
	// Failure - the pnode has a type, and it isn't ours
	matched = false;
      } else {
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	if ((pn->current_type_record->current_load + vn->typecount) >
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	    pn->current_type_record->max_load) {
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	  // This would put us over its max load
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	  //if (allow_overload && (tr->max_load > 1) &&
	  //    ((pn->current_type_record->current_load + vn->typecount) <
	  //    (pn->current_type_record->max_load + 2))) {
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	  if (allow_overload && (tr->max_load > 1)) {
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	    // That's okay, we're allowing overload
	    matched = true;
	  } else {
	    // Failure - the type is right, but the pnode is full
	    matched = false;
	  }
	} else {
	  // It's under its max load, we can fit in
	  matched = true;
	}
      }
    } else {
      // pnode doesn't have a type
      matched = true;
    }
  }

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  // Commented out for now because it's too slow!
#if 0
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  // Check for 'local' desires - the reason we take the time to do this here is
  // that they are actually, in many ways, like types with vn->typecount > 1.
  if (matched && !vn->desires.empty()) {
    tb_vnode::desires_map::iterator desire_it;
    for (desire_it = vn->desires.begin();
	desire_it != vn->desires.end();
	desire_it++) {
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      if (desire_it->is_l_additive() {
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      tb_pnode::features_map::iterator feature_it =
	pn->features.find(desire_it->first);
      if (feature_it == pn->features.end()) {
	matched = false;
	break;
      }
      // If we are allowing overloading, do so only to a limited degree
      if (allow_overload) {
	if ((feature_it->second < desire_it->second)
	    && (feature_it->second - desire_it->second)
	        < (desire_it->second * 2)) {
	  matched = false;
	  break;
	}
      } else {
	// No overloading, and this would put us over the limit
	if (feature_it->second < desire_it->second) {
	  matched = false;
	  break;
	}
      }
    }
  }
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#endif
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  return matched;
}

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/*
 * Finds a pnode which:
 * 1) One of the vnode's neighbors is mapped to
 * 2) Satisifies the usual pnode mapping constraints
 * 3) The vnode is not already mapped to
 */
tb_pnode *find_pnode_connected(vvertex vv, tb_vnode *vn) {

  //cerr << "find_pnode_connected(" << vn->name << ") called" << endl;

  // We make a list of all neighboring vnodes so that we can go through
  // them in random order
  vector<vedge> visit_order(out_degree(vv,VG));
  voedge_iterator vedge_it,end_vedge_it;
  tie(vedge_it,end_vedge_it) = out_edges(vv,VG);	    
  for (int i = 0; vedge_it != end_vedge_it; vedge_it++, i++) {
    visit_order[i] = *vedge_it;
  }
  for (int i = 0; i < visit_order.size(); i++) {
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	int i1 = RANDOM() % visit_order.size();
	int i2 = RANDOM() % visit_order.size();
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	vedge tmp = visit_order[i1];
	visit_order[i1] = visit_order[i2];
	visit_order[i2] = tmp;
  }
  for (int i = 0; i < visit_order.size(); i++) {
    vvertex neighbor_vv = target(visit_order[i],VG);
    tb_vnode *neighbor_vn = get(vvertex_pmap,neighbor_vv);
    //cerr << "    trying " << neighbor_vn->name << endl;
    // Skip any that aren't assigned
    if (!neighbor_vn->assigned) {
      //cerr << "        not assigned" << endl;
      continue;
    }

    // Skip any that are assigned to the same pnode we are
    if (neighbor_vn->assignment == vn->assignment) {
      //cerr << "        same assignment" << endl;
      continue;
    }

    // Check to make sure that our vn can map to the neibor's assigment
    tb_pnode *neighbor_pnode = get(pvertex_pmap,neighbor_vn->assignment);
    //cerr << "        neighbor on " << neighbor_pnode->name << endl;
    if (pnode_is_match(vn,neighbor_pnode)) {
      //cerr << "        good" << endl;
      //cerr << "    worked" << endl;
      return neighbor_pnode;
    }
    //cerr << "        doesn't match" << endl;
  }

  //cerr << "    failed" << endl;
  return NULL;
}

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tb_pnode *find_pnode(tb_vnode *vn)
{
#ifdef PER_VNODE_TT
  tt_entry tt = vnode_type_table[vn->name];
#else
  tt_entry tt = type_table[vn->type];
#endif
  int num_types = tt.first;
  pclass_vector *acceptable_types = tt.second;
  
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  tb_pnode *newpnode = NULL;
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  //cerr << "Node is " << vn->name << " First = " << first << endl;
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  // Randomize the order in which we go through the list of acceptable pclasses
  // We do this by making a randomly-ordered list of indicies into the
  // acceptable_types vector
  vector<int> traversal_order(num_types);
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  for (int i = 0; i < num_types; i++) {
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	traversal_order[i] = i;
  }
  for (int i = 0; i < num_types; i++) {
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	int i1 = RANDOM() % num_types;
	int i2 = RANDOM() % num_types;
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	int tmp = traversal_order[i1];
	traversal_order[i1] = traversal_order[i2];
	traversal_order[i2] = tmp;
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  }
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  for (int i = 0; i < num_types; i++) {
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    int index = traversal_order[i];
    tb_pclass *pclass = (*acceptable_types)[index];
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    // Skip pclasses that have been disabled
    if (pclass->disabled) {
	  continue;
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    }
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#ifndef FIND_PNODE_SEARCH
    // If not searching for the pnode, just grab the front one
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    newpnode = pclass->members[vn->type]->front();
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#else
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#ifdef PER_VNODE_TT
    // If using PER_VNODE_TT and vclasses, it's possible that there are
    // some pclasses in this node's type table that can't be used right now,
    // becuase they contain entires that don't contain the vnodes _current_
    // type
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    if (pclass->members.find(vn->type) == pclass->members.end()) {
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	continue;
    }
#endif
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    list<tb_pnode*>::iterator it = pclass->members[vn->type]->L.begin();
    while (it != pclass->members[vn->type]->L.end()) {
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	if (pnode_is_match(vn,*it)) {
	    break; 
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	} else {
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	    it++;
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	}
    }
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    if (it == pclass->members[vn->type]->L.end()) {
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	newpnode = NULL;
    } else {
	newpnode = *it;
    }
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#endif // FIND_PNODE_SEARCH
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#ifdef PCLASS_DEBUG
    cerr << "Found pclass: " <<
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      pclass->name << " and node " <<
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      (newpnode == NULL ? "NULL" : newpnode->name) << "\n";
#endif
    if (newpnode != NULL) {
      RDEBUG(cout << " to " << newpnode->name << endl;)
      return newpnode;
    }
  }
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  // Nope, didn't find one
  return NULL;
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}

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// We put the temperature outside the function so that external stuff, like
// status_report in assign.cc, can see it.
double temp;
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/* When this is finished the state will reflect the best solution found. */
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void anneal(bool scoring_selftest, double scale_neighborhood,
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	double *initial_temperature, double use_connected_pnode_find)
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{
  cout << "Annealing." << endl;

  double newscore = 0;
  double bestscore = 0;
 
  // The number of iterations that took place.
  iters = 0;
  iters_to_best = 0;
  int accepts = 0;
  
  double scorediff;

  int nnodes = num_vertices(VG);
  int npnodes = num_vertices(PG);
  int npclasses = pclasses.size();
  
  float cycles = CYCLES*(float)(nnodes + num_edges(VG) + PHYSICAL(npnodes));
  float optimal = OPTIMAL_SCORE(num_edges(VG),nnodes);
    
#ifdef STATS
  cout << "STATS_OPTIMAL = " << optimal << endl;
#endif

  int mintrans = (int)cycles;
  int trans;
  int naccepts = 20*(nnodes + PHYSICAL(npnodes));
  pvertex oldpos;
  bool oldassigned;
  int bestviolated;
  int num_fixed=0;
  double meltedtemp;
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  temp = init_temp;
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  double deltatemp, deltaavg;

  // Priority queue of unassigned virtual nodes.  Basically a fancy way
  // of randomly choosing a unassigned virtual node.  When nodes become
  // unassigned they are placed in the queue with a random priority.
  vvertex_int_priority_queue unassigned_nodes;

#ifdef VERBOSE
  cout << "Initialized to cycles="<<cycles<<" optimal="<<optimal<<" mintrans="
       << mintrans<<" naccepts="<<naccepts<< endl;
#endif

  /* Set up the initial counts */
  init_score();

  /* Set up fixed nodes */
  for (name_name_map::iterator fixed_it=fixed_nodes.begin();
       fixed_it!=fixed_nodes.end();++fixed_it) {
    if (vname2vertex.find((*fixed_it).first) == vname2vertex.end()) {
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      cout << "Fixed node: " << (*fixed_it).first <<
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	" does not exist." << endl;
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      exit(EXIT_UNRETRYABLE);
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    }
    vvertex vv = vname2vertex[(*fixed_it).first];
    if (pname2vertex.find((*fixed_it).second) == pname2vertex.end()) {
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      cout << "Fixed node: " << (*fixed_it).second <<
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	" not available." << endl;
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      exit(EXIT_UNRETRYABLE);
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    }
    pvertex pv = pname2vertex[(*fixed_it).second];
    tb_vnode *vn = get(vvertex_pmap,vv);
    tb_pnode *pn = get(pvertex_pmap,pv);
    if (vn->vclass != NULL) {
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      cout << "Can not have fixed nodes be in a vclass!.\n";
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      exit(EXIT_FATAL);
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    }
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    if (add_node(vv,pv,false,true) == 1) {
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      cout << "Fixed node: Could not map " << vn->name <<
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	" to " << pn->name << endl;
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      exit(EXIT_UNRETRYABLE);
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    }
    vn->fixed = true;
    num_fixed++;
  }

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  // Subtract the number of fixed nodes from nnodes, since they don't really
  // count
  if (num_fixed) {
      cout << "Adjusting dificulty estimate for fixed nodes, " <<
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	  (nnodes - num_fixed) << " remain.\n";
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  }

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  /* We'll check against this later to make sure that whe we've unmapped
   * everything, the score is the same */
  double initial_score = get_score();

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  /*
   * Handle node hints - we do this _after_ we've figured out the initial
   * score, since, unlike fixed nodes, hints get unmapped before we do the
   * final mapping. Also, we ignore any hints for vnodes which have already
   * been assigned - they must have been fixed, and that over-rides the hint.
   */
  for (name_name_map::iterator hint_it=node_hints.begin();
       hint_it!=node_hints.end();++hint_it) {
    if (vname2vertex.find((*hint_it).first) == vname2vertex.end()) {
      cout << "Warning: Hinted node: " << (*hint_it).first <<
	"does not exist." << endl;
      continue;
    }
    vvertex vv = vname2vertex[(*hint_it).first];
    if (pname2vertex.find((*hint_it).second) == pname2vertex.end()) {
      cout << "Warning: Hinted node: " << (*hint_it).second <<
	" not available." << endl;
      continue;
    }
    pvertex pv = pname2vertex[(*hint_it).second];
    tb_vnode *vn = get(vvertex_pmap,vv);
    tb_pnode *pn = get(pvertex_pmap,pv);
    if (vn->assigned) {
      cout << "Warning: Skipping hint for node " << vn->name << ", which is "
	<< "fixed in place" << endl;
      continue;
    }
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    if (add_node(vv,pv,false,false) == 1) {
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      cout << "Warning: Hinted node: Could not map " << vn->name <<
	" to " << pn->name << endl;
      continue;
    }
  }

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  bestscore = get_score();
  bestviolated = violated;

#ifdef VERBOSE
  cout << "Problem started with score "<<bestscore<<" and "<< violated
       << " violations." << endl;
#endif

  absbest = bestscore;
  absbestviolated = bestviolated;

  vvertex_iterator vit,veit;
  tie(vit,veit) = vertices(VG);
  for (;vit!=veit;++vit) {
    tb_vnode *vn = get(vvertex_pmap,*vit);
    absassigned[*vit] = vn->assigned;
    if (vn->assigned) {
      absassignment[*vit] = vn->assignment;
      abstypes[*vit] = vn->type;
    } else {
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      unassigned_nodes.push(vvertex_int_pair(*vit,RANDOM()));
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    }
  }

  int neighborsize;
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  neighborsize = (nnodes - num_fixed) * npclasses;
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  if (neighborsize < min_neighborhood_size) {
    neighborsize = min_neighborhood_size;
  }
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  // Allow scaling of the neighborhood size, so we can make assign try harder
  // (or less hard)
  neighborsize = (int)(neighborsize * scale_neighborhood);

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#ifdef CHILL
  double scores[neighborsize];
#endif

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  if (num_fixed >= nnodes) {
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    cout << "All nodes are fixed.  No annealing." << endl;
    goto DONE;
  }
  
  // Annealing loop!
  vvertex vv;
  tb_vnode *vn;

  // Crap added by ricci
  bool melting;
  int nincreases, ndecreases;
  double avgincrease;
  double avgscore;
  double initialavg;
  double stddev;
  bool finished;
  bool forcerevert;
  finished = forcerevert = false;
  int tsteps;
  int mintsteps;
  double meltstart;

#define MAX_AVG_HIST 16
  double avghist[MAX_AVG_HIST];
  int hstart, nhist;
  hstart = nhist = 0;
  double lasttemp;
  double smoothedavg, lastsmoothed;
  lastsmoothed = 500000.0f;
  lasttemp = 5000.0f;
  int melttrials;
  melttrials = 0;

  bool finishedonce;
  finishedonce = false;

  tsteps = 0;
  mintsteps = MAX_AVG_HIST;
  tsteps = 0;
  mintsteps = MAX_AVG_HIST;
  tsteps = 0;
  mintsteps = MAX_AVG_HIST;

  // Make sure the last two don't prevent us from running!
  avgscore = initialavg = 1.0;

  stddev = 0;

#ifdef MELT
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  if (initial_temperature == NULL) {
      melting = true;
  } else {
      melting = false;
      temp = *initial_temperature;
      cout << "Starting with initial temperature " << temp << endl;
  }
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#ifdef TIME_TARGET
  meltstart = used_time();
#endif
#else
  melting = false;
#endif

  melt_trans = neighborsize;
#ifdef EPSILON_TERMINATE
  while(1) {
#else
  while (temp >= temp_stop) {
#endif
#ifdef VERBOSE
    cout << "Temperature:  " << temp << " AbsBest: " << absbest <<
      " (" << absbestviolated << ")" << endl;
#endif
    trans = 0;
    accepts = 0;
    nincreases = ndecreases = 0;
    avgincrease = 0.0;
    avgscore = bestscore;
#ifdef CHILL
    scores[0] = bestscore;
#endif

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    // Adjust the number of transitions we're going to do based on the number
    // of pclasses that are actually 'in play'
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    int transitions = (int)(neighborsize *
      (count_enabled_pclasses() *1.0 / pclasses.size()));
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    assert(transitions <= neighborsize);

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    if (melting) {
      cout << "Doing melting run" << endl;
    }

    while ((melting && (trans < melt_trans))
#ifdef NEIGHBOR_LENGTH
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	    || (trans < transitions)) {
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#else
	    || (!melting && (trans < mintrans && accepts < naccepts))) {
#endif

#ifdef STATS
      cout << "STATS temp:" << temp << " score:" << get_score() <<
	" violated:" << violated << " trans:" << trans <<
	" accepts:" << accepts << " current_time:" <<
	used_time() << endl;
#endif 
      pvertex newpos;
      trans++;
      iters++;

      bool freednode = false;
      if (! unassigned_nodes.empty()) {
	vv = unassigned_nodes.top().first;
	assert(!get(vvertex_pmap,vv)->assigned);
	unassigned_nodes.pop();
      } else {
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	int start = RANDOM()%nnodes;
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	int choice = start;
	while (get(vvertex_pmap,virtual_nodes[choice])->fixed) {
	  choice = (choice +1) % nnodes;
	  if (choice == start) {
	      choice = -1;
	      break;
	  }
	}
	if (choice >= 0) {
	    vv = virtual_nodes[choice];
	} else {
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	    cout << "**** Error, unable to find any non-fixed nodes" << endl;
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	    goto DONE;
	}
      }
      
      vn = get(vvertex_pmap,vv);
      RDEBUG(cout << "Reassigning " << vn->name << endl;)
      oldassigned = vn->assigned;
      oldpos = vn->assignment;
      
#ifdef FREE_IMMEDIATELY
      if (oldassigned) {
	remove_node(vv);
	RDEBUG(cout << "Freeing up " << vn->name << endl;)
      }
#endif
      
      if (vn->vclass != NULL) {
	vn->type = vn->vclass->choose_type();
#ifdef SCORE_DEBUG
	cerr << "vclass " << vn->vclass->name  << ": choose type for " <<
	    vn->name << " = " << vn->type << " dominant = " <<
	    vn->vclass->dominant << endl;
#endif
      }
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      // Actually find a pnode
      tb_pnode *newpnode = NULL;
      if ((use_connected_pnode_find != 0)
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	  && ((RANDOM() % 1000) < (use_connected_pnode_find * 1000))) {
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	newpnode = find_pnode_connected(vv,vn);
      }
      if (newpnode == NULL) {
	newpnode = find_pnode(vn);
      }
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#ifndef FREE_IMMEDIATELY
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      if (oldassigned) {
	RDEBUG(cout << "removing: !lan, oldassigned" << endl;)
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	  remove_node(vv);
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      }
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#endif
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      if (newpnode == NULL) {
	// We're not going to be re-assigning this one
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#ifndef SMART_UNMAP
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	unassigned_nodes.push(vvertex_int_pair(vv,RANDOM()));
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#endif
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	// need to free up nodes
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#ifdef SMART_UNMAP
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	// XXX: Should probably randomize this
	// XXX: Add support for not using PER_VNODE_TT
	// XXX: Not very robust

	freednode = true;

	tt_entry tt = vnode_type_table[vn->name];
	int size = tt.first;
	pclass_vector *acceptable_types = tt.second;
	// Find a node to kick out
	bool foundnode = false;
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	int offi = RANDOM();
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	int index;
	for (int i = 0; i < size; i++) {
	  index = (i + offi) % size;
	  if ((*acceptable_types)[index]->used_members.find(vn->type) ==
	      (*acceptable_types)[index]->used_members.end()) {
	    continue;
	  }
	  if ((*acceptable_types)[index]->used_members[vn->type]->size() == 0) {
	    continue;
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	  }
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	  foundnode = true;
	  break;
	}
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	if (foundnode) {
	  assert((*acceptable_types)[index]->used_members[vn->type]->size());
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	  tb_pclass::tb_pnodeset::iterator it =
	    (*acceptable_types)[index]->used_members[vn->type]->begin();
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	  int j = RANDOM() %
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	    (*acceptable_types)[index]->used_members[vn->type]->size();
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	  while (j > 0) {
	    it++;
	    j--;
	  }
	  tb_vnode_set::iterator it2 = (*it)->assigned_nodes.begin();
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	  int k = RANDOM() % (*it)->assigned_nodes.size();
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	  while (k > 0) {
	    it2++;
	    k--;
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	  }
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	  tb_vnode *kickout = *it2;
	  assert(kickout->assigned);
	  vvertex toremove = vname2vertex[kickout->name];
	  newpnode = *it;
	  remove_node(toremove);
	  unassigned_nodes.push(vvertex_int_pair(toremove,
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		RANDOM()));
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	} else {
	  cerr << "Failed to find a replacement!" << endl;
	}
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#else
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	int start = RANDOM()%nnodes;
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	int toremove = start;
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#ifdef SMART_UNMAP

#ifdef PER_VNODE_TT
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	  tt_entry tt = vnode_type_table[vn->name];
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#else
	  tt_entry tt = type_table[vn->type];
#endif
	  pclass_vector *acceptable_types = tt.second;

	  while (1) {
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	    bool keepgoing = false;
	    if (get(vvertex_pmap,virtual_nodes[toremove])->fixed) {
	      keepgoing = true;
	    } else if (! get(vvertex_pmap,virtual_nodes[toremove])->assigned) {
	      keepgoing = true;
	    } else {
	      pvertex pv = get(vvertex_pmap,virtual_nodes[toremove])->assignment;
	      tb_pnode *pn = get(pvertex_pmap,pv);
	      int j;
	      for (j = 0; j < acceptable_types->size(); j++) {
		if ((*acceptable_types)[j] == pn->my_class) {
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		  break;
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		}
	      }
	      if (j == acceptable_types->size()) {
		keepgoing = true;
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	      }
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	    }

	    if (!keepgoing) {
	      break;
	    }

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#else
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	    while (get(vvertex_pmap,virtual_nodes[toremove])->fixed ||
		(! get(vvertex_pmap,virtual_nodes[toremove])->assigned)) {
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#endif
	      toremove = (toremove +1) % nnodes;
	      if (toremove == start) {
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		toremove = -1;
		break;
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	      }
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	    }
	    if (toremove >= 0) {
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	      RDEBUG(cout << "removing: freeing up nodes" << endl;)
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		remove_node(virtual_nodes[toremove]);
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	      unassigned_nodes.push(vvertex_int_pair(virtual_nodes[toremove],
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		    RANDOM()));
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	    }
	    continue;
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#endif /* SMART_UNMAP */
#ifndef SMART_UNMAP
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	  } else {
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#else
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	  }
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#endif
	  if (newpnode != NULL) {
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	    newpos = pnode2vertex[newpnode];
	    if (scoring_selftest) {
	      // Run a little test here - see if the score we get by adding
	      // this node, then removing it, is the same one we would have
	      // gotten otherwise
	      double oldscore = get_score();
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	      int oldviolated = violated;
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	      double tempscore;
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	      int tempviolated;
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	      if (!add_node(vv,newpos,false,false)) {
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		tempscore = get_score();
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		tempviolated = violated;
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		remove_node(vv);
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	      }
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	      if ((oldscore != get_score()) || (oldviolated != violated)) {
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		cerr << "Scoring problem adding a mapping - oldscore was " <<
		  oldscore <<  " newscore is " << newscore << " tempscore was "
		  << tempscore << endl;
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		cerr << "oldviolated was " << oldviolated << " newviolated is "
		  << violated << " tempviolated was " << tempviolated << endl;
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		cerr << "I was tring to map " << vn->name << " to " <<
		  newpnode->name << endl;
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		print_solution();
		cerr << vinfo;
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		abort();
	      }
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	    }
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	    if (add_node(vv,newpos,false,false) != 0) {
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	      unassigned_nodes.push(vvertex_int_pair(vv,RANDOM()));
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	      continue;
	    }
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	  } else {
#ifdef SMART_UNMAP
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	    unassigned_nodes.push(vvertex_int_pair(vv,RANDOM()));
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#endif
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	    if (freednode) {
	      continue;
	    }
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	  }
#ifndef SMART_UNMAP
	}
#endif

      newscore = get_score();
      assert(newscore >= 0);

      // Negative means bad
      scorediff = bestscore - newscore;
      // This looks funny, because < 0 means worse, which means an increase in
      // score
      if (scorediff < 0) {
	nincreases++;
	avgincrease = avgincrease * (nincreases -1) / nincreases +
	  (-scorediff)  / nincreases;
      } else {
	ndecreases++;
      }
      
      bool accepttrans = false;
      if (newscore < optimal) {
	  accepttrans = true;
	  RDEBUG(cout << "accept: optimal (" << newscore << "," << optimal
		  << ")" << endl;)
      } else if (melting) {
	  accepttrans = true;
	  RDEBUG(cout << "accept: melting" << endl;)
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      } else {
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#ifdef NO_VIOLATIONS
	  if (newscore < bestscore) {
	      accepttrans = true;
	      RDEBUG(cout << "accept: better (" << newscore << "," << bestscore
		      << ")" << endl;)
	  } else if (accept(scorediff,temp)) {
	      accepttrans = true;
	      RDEBUG(cout << "accept: metropolis (" << newscore << ","
		      << bestscore << "," << expf(scorediff/(temp*sensitivity))
		      << ")" << endl;)
	  }
#else
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#ifdef SPECIAL_VIOLATION_TREATMENT
	  /*
	   * In this ifdef, we always accept new solutions that have fewer
	   * violations than the old solution, and when we're trying to
	   * determine whether or not to accept a new solution with a higher
	   * score, we don't take violations into the account.
	   *
	   * The problem with this shows up at low temperatures. What can often
	   * happen is that we accept a solution with worse violations but a
	   * better (or similar) score. Then, if we were to try, say the first
	   * solution (or a score-equivalent one) again, we'd accept it again.
	   *
	   * What this leads to is 'thrashing', where we have a whole lot of
	   * variation of scores over time, but are not making any real
	   * progress. This prevents the cooling schedule from converging for
	   * much, much longer than it should really take.
	   */
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          if ((violated == bestviolated) && (newscore < bestscore)) {
	      accepttrans = true;
	      RDEBUG(cout << "accept: better (" << newscore << "," << bestscore
		      << ")" << endl;)
	  } else if (violated < bestviolated) {
	      accepttrans = true;
	      RDEBUG(cout << "accept: better (violations) (" << newscore << ","
		      << bestscore << "," << violated << "," << bestviolated
		      << ")" << endl;
	          cout << "Violations: (new) " << violated << endl;
		  cout << vinfo;)
	  } else if (accept(scorediff,temp)) {
	      accepttrans = true;
	      RDEBUG(cout << "accept: metropolis (" << newscore << ","
		      << bestscore << "," << expf(scorediff/(temp*sensitivity))
		      << ")" << endl;)
	  }
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#else // no SPECIAL_VIOLATION_TREATMENT
	  /*
	   * In this branch of the ifdef, we give violations no special
	   * treatment when it comes to accepting new solution - we just add
	   * them into the score. This makes assign behave in a more 'classic'
	   * simulated annealing manner.
	   *
	   * One consequence, though, is that we have to be more careful with
	   * scores. We do not want to be able to get into a situation where
	   * adding a violation results in a _lower_ score than a solution with
	   * fewer violations.
	   */
          double adjusted_new_score = newscore + violated * VIOLATION_SCORE;
	  double adjusted_old_score = bestscore + bestviolated *
	      VIOLATION_SCORE;

	  if (adjusted_new_score < adjusted_old_score) {
	    accepttrans = true;
	  } else if (accept(adjusted_old_score - adjusted_new_score,temp)) {
	    accepttrans = true;
	  }

#endif // SPECIAL_VIOLATION_TREATMENT

      }
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#endif

      if (accepttrans) {
	bestscore = newscore;
	bestviolated = violated;
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#ifdef GNUPLOT_OUTPUT
	fprintf(tempout,"%f\n",temp);
	fprintf(scoresout,"%f\n",newscore);
	fprintf(deltaout,"%f\n",-scorediff);
#endif
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	avgscore += newscore;

	accepts++;

#ifdef CHILL
	 if (!melting) {
	     scores[accepts] = newscore;
	 }
#endif

#ifdef NO_VIOLATIONS
	if (newscore < absbest) {
#else
	if ((violated < absbestviolated) ||
	    ((violated == absbestviolated) &&
	     (newscore < absbest))) {
#endif
#ifdef SCORE_DEBUG
	  cerr << "New best solution." << endl;
#endif
	  tie(vit,veit) = vertices(VG);
	  for (;vit!=veit;++vit) {
	    absassignment[*vit] = get(vvertex_pmap,*vit)->assignment;
	    absassigned[*vit] = get(vvertex_pmap,*vit)->assigned;
	    abstypes[*vit] = get(vvertex_pmap,*vit)->type;
	  }
	  absbest = newscore;
	  absbestviolated = violated;
	  iters_to_best = iters;
#ifdef SCORE_DEBUG
	  cerr << "New best recorded" << endl;
#endif
	}
	if (newscore < optimal) {
	  cout << "OPTIMAL ( " << optimal << ")" << endl;
	  goto DONE;
	}
	// Accept change
      } else {
	// Reject change
	RDEBUG(cout << "removing: rejected change" << endl;)
	remove_node(vv);
	if (oldassigned) {
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	  add_node(vv,oldpos,false,false);
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	}
      }

      if (melting) {
	temp = avgincrease /
	  log(nincreases/ (nincreases * X0 - ndecreases * (1 - X0)));
	if (!(temp > 0.0)) {
	    temp = 0.0;
	}
      }
#ifdef TIME_TERMINATE
      if (timelimit && ((used_time() - timestart) > timelimit)) {
	printf("Reached end of run time, finishing\n");
	forcerevert = true;
	finished = true;
	goto NOTQUITEDONE;
      }
#endif

    }

#ifdef RANDOM_ASSIGNMENT
      if (violated == 0) {
	  finished = true;
      }
#endif

#ifdef REALLY_RANDOM_ASSIGNMENT
      if (unassigned_nodes.size() == 0) {
	  finished = true;
      }
#endif

NOTQUITEDONE:
      RDEBUG(printf("avgscore: %f = %f / %i\n",avgscore / (accepts +1),avgscore,accepts+1);)
      avgscore = avgscore / (accepts +1);

    if (melting) {
      melting = false;
      initialavg = avgscore;
      meltedtemp = temp;
      RDEBUG(cout << "Melting finished with a temperature of " << temp
	<< " avg score was " << initialavg << endl;)
      if (!(meltedtemp > 0.0)) { // This backwards expression to catch NaNs
	cout << "Finished annealing while melting!" << endl;
	finished = true;
	forcerevert = true;
      }
#ifdef TIME_TARGET
      if (timetarget) {
	double melttime = used_time() - meltstart;
	double timeleft = timetarget - melttime;
	double stepsleft = timeleft / melttime;
	cout << "Melting took " << melttime << " seconds, will try for "
	  << stepsleft << " temperature steps" << endl;
	temp_rate = pow(temp_stop/temp,1/stepsleft);
	cout << "Timelimit: " << timelimit << " Timeleft: " << timeleft
	  << " temp_rate: " << temp_rate << endl;
      }
#endif
    } else {
#ifdef CHILL
      if (!melting) {
	  stddev = 0;
	  for (int i = 0; i <= accepts; i++) {
	    stddev += pow(scores[i] - avgscore,2);
	  }
	  stddev /= (accepts +1);
	  stddev = sqrt(stddev);
	  temp = temp / (1 + (temp * log(1 + delta))/(3  * stddev));
      }
#else
      temp *= temp_rate;
#endif
    }


#ifdef DEBUG_TSTEP
#ifdef EPSILON_TERMINATE
#ifdef CHILL
    RDEBUG(printf("temp_end: %f %f %f\n",temp,temp * avgscore / initialavg,stddev);)
#else
    RDEBUG(printf("temp_end: %f %f\n",temp,temp * avgscore / initialavg);)
#endif
#else
    printf("temp_end: %f ",temp);
    if (trans >= mintrans) {
	if (accepts >= naccepts) {
	    printf("both");
	} else {
	    printf("trans %f",accepts*1.0/naccepts);
	}
    } else {
	printf("accepts %f",trans*1.0/mintrans);
    }
    printf("\n");
#endif
#endif
    
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    RDEBUG(
    printf("temp_end: temp: %f ratio: %f stddev: %f\n",temp,temp * avgscore / initialavg,stddev);
    );
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    // Add this to the history, and computed a smoothed average
    smoothedavg = avgscore / (nhist + 1);
    for (int j = 0; j < nhist; j++) {
      smoothedavg += avghist[(hstart + j) % MAX_AVG_HIST] / (nhist + 1);
    }

    avghist[(hstart + nhist) % MAX_AVG_HIST] = avgscore;
    if (nhist < MAX_AVG_HIST) {
      nhist++;
    } else {
      hstart = (hstart +1) % MAX_AVG_HIST;
    }

#ifdef LOCAL_DERIVATIVE
    deltaavg = lastsmoothed - smoothedavg;
    deltatemp = lasttemp - temp;
#else
    deltaavg = initialavg - smoothedavg;
    deltatemp = meltedtemp - temp;
#endif

    lastsmoothed = smoothedavg;
    lasttemp = temp;

#ifdef EPSILON_TERMINATE
    RDEBUG(
       printf("avgs: real: %f, smoothed %f, initial: %f\n",avgscore,smoothedavg,initialavg);
       printf("epsilon: (%f) %f / %f * %f / %f < %f (%f)\n", fabs(deltaavg), temp, initialavg,
	   deltaavg, deltatemp, epsilon,(temp / initialavg) * (deltaavg/ deltatemp));
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    );
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    if ((tsteps >= mintsteps) &&
#ifdef ALLOW_NEGATIVE_DELTA
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	((temp < 0) || isnan(temp) ||
//	 || (fabs((temp / initialavg) * (deltaavg/ deltatemp)) < epsilon))) {
	 ((temp / initialavg) * (deltaavg/ deltatemp)) < epsilon)) {
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#else
	(deltaavg > 0) && ((temp / initialavg) * (deltaavg/ deltatemp) < epsilon)) {
#endif
#ifdef FINISH_HILLCLIMB
        if (!finishedonce && ((absbestviolated <= violated) && (absbest < bestscore))) {
	    // We don't actually stop, we just go do a hill-climb (basically) at the best
	    // one we previously found
	    finishedonce = true;
	    printf("Epsilon Terminated, but going back to a better solution\n");
	} else {
	    finished = true;
	}
#else
	finished = true;
#endif
	forcerevert = true;
    }
#endif

    bool revert = false;
    if (forcerevert) {
	cout << "Reverting: forced" << endl;
	revert = true;
    }

#ifndef NO_REVERT
    if (REVERT_VIOLATIONS && (absbestviolated < violated)) {
	cout << "Reverting: REVERT_VIOLATIONS" << endl;
	revert = true;
    }
    if (absbest < bestscore) {
	cout << "Reverting: best score" << endl;
	revert = true;
    }
#endif

    if (REVERT_LAST && (temp < temp_stop)) {
	cout << "Reverting: REVERT_LAST" << endl;
	revert = true;
    }

    // Only revert if the best configuration has better violations
    vvertex_list lan_nodes;
    vvertex_iterator vvertex_it,end_vvertex_it;
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    if (revert) {
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      cout << "Reverting to best solution\n";
      // Do a full revert
      tie(vvertex_it,end_vvertex_it) = vertices(VG);
      for (;vvertex_it!=end_vvertex_it;++vvertex_it) {
	tb_vnode *vnode = get(vvertex_pmap,*vvertex_it);
	if (vnode->fixed) continue;
	if (vnode->assigned) {
	  RDEBUG(cout << "removing: revert " << vnode->name << endl;)
	  remove_node(*vvertex_it);
	} else {
	  RDEBUG(cout << "not removing: revert " << vnode->name << endl;)
	}
      }
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      // Check to make sure that our 'clean' solution scores the same as
      // the initial score - if not, that indicates a bug
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      if (!compare_scores(get_score(),initial_score)) {
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	  cout << "*** WARNING: 'Clean' score does not match initial score" <<
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	      endl << "     This indicates a bug - contact the operators" <<
	      endl << "     (initial score: " << initial_score <<
	      ", current score: " << get_score() << ")" << endl;
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	  // One source of this can be pclasses that are still used - check for
	  // those
	  pclass_list::iterator pit = pclasses.begin();
	  for (;pit != pclasses.end();pit++) {
	      if ((*pit)->used_members != 0) {
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		  cout << (*pit)->name << " is " << (*pit)->used_members
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		      << "% used" << endl;
	      }
	  }
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      }
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      tie(vvertex_it,end_vvertex_it) = vertices(VG);
      for (;vvertex_it!=end_vvertex_it;++vvertex_it) {
	tb_vnode *vnode = get(vvertex_pmap,*vvertex_it);
	if (vnode->fixed) continue;
	if (absassigned[*vvertex_it]) {
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	  if (vnode->vclass != NULL) {
	    vnode->type = abstypes[*vvertex_it];
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	  }
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	  assert(!add_node(*vvertex_it,absassignment[*vvertex_it],true,false));
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	}
      }
    }

    tsteps++;

    if (finished) {
      goto DONE;
    }
  }
 DONE:
  cout << "Done" << endl;
}