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specialtsp.c
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#include "structs.h"
#include "specialtsp.h"
#include "math.h"
/* Solves TSP exactly by dfs with pruning, using the lower bound
suggested by Sankoff and Blanchette */
void
ap_rec_dfs ( int ncount, int *degree, int **weights, int **status,
int *stack, int *outcycle, int *best, int score,
int picked, smalledge_t * edges, int numedges, int *otherEnd,
int level )
{
/* use ordering of edges; left branch is include,
right branch is exclude; do a dfs of the tree (so that include
always gets explored first), keeping the best so far and using
that and the lower bound to prune branches */
int num_genes;
int lb_new;
int i, j, inc;
int new_i = -1, new_j = -1;
int orig_status;
int otherEndI, otherEndJ;
smalledge_t *newedge = NULL;
num_genes = ncount / 2;
#ifdef VERBOSE
fprintf ( outfile, "level: %3d, picked: %3d, score: %7d, best: %7d\n",
level, picked, score, *best );
#ifdef VERYVERBOSE
fprintf ( outfile, "Degrees:\n" );
for ( i = -num_genes; i <= num_genes; i++ )
{
fprintf ( outfile, "degree of %3d is %2d", i, degree[i] );
fprintf ( outfile, "\n" );
}
fflush ( outfile );
#endif
#endif
fflush ( outfile );
/* Is tour complete? (we cannot create bad tours) */
if ( picked == ncount )
{ /* uncommon, I presume */
#ifdef VERBOSE
fprintf ( outfile, "found a full solution\n" );
#endif
fflush ( outfile );
/* yes, so we reached bottom of recursion */
/* is the new solution better (smaller) ? */
if ( score < *best )
{
#ifdef VERBOSE
fprintf ( outfile, "found a better full solution\n" );
fflush ( outfile );
#endif
/* yes, so copy stack to outcycle */
for ( i = 0; i < ncount; i++ )
{
outcycle[i] = stack[i];
#ifdef VERBOSE
fprintf ( outfile, "outcycle[%3d]=%3d\n", i, outcycle[i] );
fflush ( outfile );
#endif
}
*best = score;
}
return;
}
/* Compute lower bound */
/* if a vertex has degree 1, add the cheapest edge still available
that is incident upon it; note that this adds twice as many edges
as needed, so we'll have to divide by 2 */
/* note: this routine is fairly expensive (quadratic in the
number of cities); the same bounds could be derived more
cheaply by forward and backward work */
/* further note: if the routine ever returns a value of at least
500,000, then it means that it was called when the remaining
edges could not complete a tour -- this should not happen */
lb_new = 0;
for ( i = 0; i < ncount; i++ )
{
if ( i < num_genes )
new_i = -( i + 1 );
else
new_i = i + 1 - num_genes;
if ( degree[new_i] == 1 )
{ /* degree 2 is done; degrees 0 & >2 impossible */
inc = 3; /* if we cannot find an edge, that's the cost */
for ( j = i + 1; j < ncount; j++ )
{
if ( j < num_genes )
new_j = -( j + 1 );
else
new_j = j + 1 - num_genes;
if ( ( status[i][j] == STAT_AVAIL ) && ( degree[new_j] == 1 )
&& ( ( otherEnd[new_i] != new_j )
|| ( picked == ncount - 1 ) )
&& ( weights[i][j] < inc ) )
inc = weights[i][j];
}
lb_new += inc; /* no usable edge of lower cost */
}
}
lb_new = lb_new / 2;
#ifdef VERBOSE
fprintf ( outfile, "lower bound=%5d\n", lb_new );
fflush ( outfile );
#endif
/* continue only if bound promises possible improvement over best-so-far */
if ( score + lb_new >= *best )
{
#ifdef VERBOSE
fprintf ( outfile, "pruning away...\n" );
fflush ( outfile );
#endif
return;
}
if ( level < numedges )
{
/* we have a chance, so get the next edge */
newedge = edges + level;
/* new_i = edges[level].I;
new_j = edges[level].J; */
new_i = newedge->I;
if ( new_i < num_genes )
new_i = -( new_i + 1 );
else
new_i = new_i + 1 - num_genes;
new_j = newedge->J;
if ( new_j < num_genes )
new_j = -( new_j + 1 );
else
new_j = new_j + 1 - num_genes;
#ifdef VERBOSE
fprintf ( outfile,
"new edge (%3d,%3d), degrees (%3d,%3d), weight %1d, otherEnd[%3d]=%3d\n",
new_i, new_j, degree[new_i], degree[new_j],
weights[newedge->I][newedge->J], new_i, otherEnd[new_i] );
fflush ( outfile );
#endif
}
/* this while loop is not too efficient at finding the next useful edge */
/* for instance, if degree[new_i]==2, then all edges (i,j) for any j
can be eliminated -- we should have a way to bump to the next i value */
while ( ( level < numedges ) &&
( ( degree[new_i] == 2 ) ||
( degree[new_j] == 2 ) ||
( ( otherEnd[new_i] == new_j ) && ( picked != ncount - 1 ) ) ) )
{ /* edge is not available, get a new one */
level++;
newedge++;
if ( level < numedges )
{
new_i = newedge->I;
if ( new_i < num_genes )
new_i = -( new_i + 1 );
else
new_i = new_i + 1 - num_genes;
new_j = newedge->J;
if ( new_j < num_genes )
new_j = -( new_j + 1 );
else
new_j = new_j + 1 - num_genes;
#ifdef VERBOSE
fprintf ( outfile,
"new edge (%3d,%3d), degrees (%3d,%3d), weight %1d, otherEnd[%3d]=%3d\n",
new_i, new_j, degree[new_i], degree[new_j],
weights[newedge->I][newedge->J], new_i,
otherEnd[new_i] );
fflush ( outfile );
#endif
}
}
if ( level == numedges )
{ /* could not find any available edge of cost <= 2
so we only have edges of cost 3 left */
/* Check if current partial solution, when completed, improves on
best so far; if so, copy it */
#ifdef VERBOSE
fprintf ( outfile, "found a partial solution\n" );
fflush ( outfile );
#endif
if ( score + ( 3 * ( ncount - picked ) ) < *best )
{
/* yes, so copy stack to outcycle */
#ifdef VERBOSE
fprintf ( outfile, "found a better partial solution\n" );
fflush ( outfile );
#endif
for ( i = 0; i < ncount; i++ )
{
outcycle[i] = stack[i];
#ifdef VERBOSE
fprintf ( outfile, "outcycle[%3d]=%3d\n", i, outcycle[i] );
fflush ( outfile );
#endif
}
*best = score + 3 * ( ncount - picked );
}
return;
}
/* we found an edge to include */
#ifdef VERYVERBOSE
fprintf ( outfile,
"level %3d, new edge (%3d,%3d), degrees (%3d,%3d), weight %1d, status %3d, otherEnd[%3d]=%3d, otherEnd[%3d]=%3d\n",
level, new_i, new_j, degree[new_i], degree[new_j],
weights[newedge->I][newedge->J], status[newedge->I][newedge->J],
new_i, otherEnd[new_i], new_j, otherEnd[new_j] );
fflush ( outfile );
#endif
/* save original status to restore before returning from recursion */
orig_status = status[newedge->I][newedge->J];
/* prepare tentative inclusion of next edge */
/* save otherEnd values to restore after call */
otherEndI = otherEnd[new_i];
otherEndJ = otherEnd[new_j];
/* recurse with edge included */
stack[picked] = level;
otherEnd[otherEndI] = otherEndJ;
otherEnd[otherEndJ] = otherEndI;
degree[new_i]++;
degree[new_j]++;
status[newedge->I][newedge->J] = STAT_INCLUDED;
#ifdef VERYVERBOSE
fprintf ( outfile, "\ninclude: " );
fflush ( outfile );
#endif
/* should guard call rather than entry */
ap_rec_dfs ( ncount, degree, weights, status, stack, outcycle, best,
score + weights[newedge->I][newedge->J], picked + 1,
edges, numedges, otherEnd, level + 1 );
/* restore otherEnd and degree info */
otherEnd[otherEndI] = new_i;
otherEnd[otherEndJ] = new_j;
degree[new_i]--;
degree[new_j]--;
/* remove edge from stack */
stack[picked] = NOEDGE;
/* set edge to be excluded */
status[newedge->I][newedge->J] = STAT_EXCLUDED;
/* recurse with edge excluded */
#ifdef VERYVERBOSE
fprintf ( outfile, "\nexclude: " );
fflush ( outfile );
#endif
ap_rec_dfs ( ncount, degree, weights, status, stack, outcycle, best,
score, picked, edges, numedges, otherEnd, level + 1 );
/* restore edge status */
status[newedge->I][newedge->J] = orig_status;
return;
}
void
ap_tsp_dfs ( int ncount, int mincost, int *found_cost, int *degree,
int **weights, int **status, intpair_t * neighbors,
int *stack, int *outcycle, int *otherEnd, smalledge_t * edges )
{
/* this is the parent routine, which takes care of initialization,
then calls the recursive dfs */
/* ncount is effectively a constant */
/* so is mincost, which is the tour cost of one of the three genomes */
/* outcycle is the returned tour */
/* pointers to arrays degree, neighbors, and otherEnd are
shifted to the middle to allow negative indexing */
/* pointers to arrays stack, outcycle, and edges are not shifted */
int num_genes;
int i, j, ind, top;
int countm3, countm2, countm1, count0, count1, count2, countL;
smalledge_t *edgesm3, *edgesm2, *edgesm1, *edges0, *edges1, *edges2,
*edgesL;
smalledge_t *newedge;
int score, best, picked, level;
int numedges;
int negEdges;
int curcity, nextcity;
int icity, jcity;
int *visited;
num_genes = ncount / 2;
/* prepare a sorted list of edges (in increasing order of cost) */
/* use distribution sort -- here ad hoc, since we only have 7 values:
-3, -2, -1, 0, 1, 2, and L = -largevalue */
/* could just use an array of pointers since adj. lists are sorted... */
/* tally values */
countL = countm3 = countm2 = countm1 = count0 = count1 = count2 = 0;
for ( i = 0; i < ncount; i++ )
for ( j = i + 1; j < ncount; j++ )
{
switch ( weights[i][j] )
{
case -3:
countm3++;
break;
case -2:
countm2++;
break;
case -1:
countm1++;
break;
case 0:
count0++;
break;
case 1:
count1++;
break;
case 2:
count2++;
break;
case 3:
break; /* don't care about these, don't count them */
default:
countL++;
break;
}
}
numedges =
countm3 + countm2 + countm1 + count0 + count1 + count2 + countL;
negEdges = countL;
edgesL = edges;
edgesm3 = edgesL + countL;
edgesm2 = edgesm3 + countm3;
edgesm1 = edgesm2 + countm2;
edges0 = edgesm1 + countm1;
edges1 = edges0 + count0;
edges2 = edges1 + count1;
for ( i = 0; i < ncount; i++ )
for ( j = i + 1; j < ncount; j++ )
{
switch ( weights[i][j] )
{
case -3:
edgesm3->I = i;
edgesm3->J = j;
edgesm3++;
break;
case -2:
edgesm2->I = i;
edgesm2->J = j;
edgesm2++;
break;
case -1:
edgesm1->I = i;
edgesm1->J = j;
edgesm1++;
break;
case 0:
edges0->I = i;
edges0->J = j;
edges0++;
break;
case 1:
edges1->I = i;
edges1->J = j;
edges1++;
break;
case 2:
edges2->I = i;
edges2->J = j;
edges2++;
break;
case 3:
break; /* don't register */
default:
edgesL->I = i;
edgesL->J = j;
edgesL++;
break;
}
}
#ifdef DEBUG
for ( i = 0; i < numedges; i++ )
fprintf ( outfile, "Edge[%3d]: (%4d, %4d), wt: %7d\n",
i, edges[i].I, edges[i].J,
weights[edges[i].I][edges[i].J] );
fprintf ( outfile, "\n" );
fflush ( outfile );
#endif
/* initialize degree to all 1s, to reflect the fact that
the (g,-g) edges are forcibly included */
for ( i = -num_genes; i < 0; i++ )
degree[i] = 1;
degree[0] = 0; /* thus will never be used */
for ( i = 1; i <= num_genes; i++ )
degree[i] = 1;
/* initialize global variables and structures */
best = 0; /* value of best solution found so far */
*found_cost = best;
score = 0; /* total value of edges picked so far */
picked = 0; /* number of edges picked so far */
level = 0;
newedge = edges;
/* Initialize otherEnd[city] to itself */
for ( i = -num_genes; i <= num_genes; i++ )
otherEnd[i] = i;
/* initially include -Z weight edges (g,-g) */
while ( weights[newedge->I][newedge->J] < -3 )
{
stack[level] = level;
i = newedge->I;
if ( i < num_genes )
i = -( i + 1 );
else
i = i + 1 - num_genes;
j = newedge->J;
if ( j < num_genes )
j = -( j + 1 );
else
j = j + 1 - num_genes;
otherEnd[i] = j;
otherEnd[j] = i;
score += weights[newedge->I][newedge->J];
picked++;
level++;
newedge++;
}
#ifdef DEBUG
if ( level != negEdges )
fprintf ( outfile, "ERROR: level: %d negEdges: %d\n", level,
negEdges );
fprintf ( outfile,
"done initializing, picked=%3d, level=%3d, score=%5d\n", picked,
level, score );
fflush ( outfile );
#endif
/* initial best solution is actually empty (beyond g/-g edges */
for ( i = negEdges; i < ncount; i++ )
stack[i] = NOEDGE; /* no such edge */
ap_rec_dfs ( ncount, degree, weights, status, stack, outcycle, &best,
score, picked, edges, numedges, otherEnd, level );
if ( best >= *found_cost )
return;
*found_cost = best;
/* outcycle at this point is a stack of edges of of cost 0, 1, or 2
in the optimal solution. Complete it into a full tour by using
whatever cost-3 edges are needed and store results in outcycle. */
visited = otherEnd; /* reuse existing space */
for ( i = -num_genes; i < 0; i++ )
visited[i] = FALSE;
visited[0] = TRUE;
for ( i = 1; i <= num_genes; i++ )
visited[i] = FALSE;
/* Set up degree array */
for ( i = negEdges; i < ncount; i++ )
{
ind = outcycle[i];
#ifdef DEBUG
fprintf ( outfile, "converting tour; outcycle[%3d]=%3d\n", i, ind );
fflush ( outfile );
#endif
if ( ind == NOEDGE )
break;
else
{
icity = edges[ind].I;
if ( icity < num_genes )
icity = -( icity + 1 );
else
icity = icity + 1 - num_genes;
jcity = edges[ind].J;
if ( jcity < num_genes )
jcity = -( jcity + 1 );
else
jcity = jcity + 1 - num_genes;
degree[icity]++;
degree[jcity]++;
}
}
#ifdef DEBUG
fprintf ( outfile, "converting tour: degrees computed are:\n" );
for ( i = -num_genes; i <= num_genes; i++ )
fprintf ( outfile, "degree[%3d]=%3d\n", i, degree[i] );
fflush ( outfile );
#endif
/* push on a stack cities of degree 1, if any */
top = 0;
for ( i = -num_genes; i <= num_genes; i++ )
{
if ( degree[i] == 1 )
{
stack[top] = i;
top++;
}
}
/* For each city, set nextcity[city] to adjacent cities */
for ( i = -num_genes; i <= num_genes; i++ )
{
neighbors[i].A = UNUSED;
neighbors[i].B = UNUSED;
}
#ifdef DEBUG
fprintf ( outfile, "converting tour: neighbors computed are:\n" );
for ( i = -num_genes; i <= num_genes; i++ )
fprintf ( outfile, "neighbors[%3d].A=%3d, neighbors[%3d].B=%3d\n", i,
neighbors[i].A, i, neighbors[i].B );
fflush ( outfile );
#endif
for ( i = 0; i < ncount; i++ )
{
ind = outcycle[i];
if ( ind == NOEDGE )
break;
else
{
icity = edges[ind].I;
if ( icity < num_genes )
icity = -( icity + 1 );
else
icity = icity + 1 - num_genes;
jcity = edges[ind].J;
if ( jcity < num_genes )
jcity = -( jcity + 1 );
else
jcity = jcity + 1 - num_genes;
if ( neighbors[icity].A == UNUSED )
neighbors[icity].A = jcity;
else
neighbors[icity].B = jcity;
if ( neighbors[jcity].A == UNUSED )
neighbors[jcity].A = icity;
else
neighbors[jcity].B = icity;
}
}
#ifdef DEBUG
fprintf ( outfile, "converting tour: neighbors computed are:\n" );
for ( i = -num_genes; i <= num_genes; i++ )
fprintf ( outfile, "neighbors[%3d].A=%3d, neighbors[%3d].B=%3d\n", i,
neighbors[i].A, i, neighbors[i].B );
fflush ( outfile );
#endif
/* Find the starting city, either a city of degree 1
or any city if all are degree 2 */
if ( top > 0 )
{
top--;
curcity = stack[top];
}
else
{
curcity = 1; /* not entirely arbitrary -- must match decode
at end of bbtsp */
}
#ifdef DEBUG
fprintf ( outfile, "converting; start city is curcity=%3d\n", curcity );
fflush ( outfile );
#endif
/* Note that city 0 may pick either of two edges, but this is okay */
outcycle[0] = curcity;
visited[curcity] = TRUE;
for ( i = 1; i < ncount; i++ )
{
if ( degree[curcity] == 2 )
{
/* Use one of the unvisited neighbors */
nextcity = neighbors[curcity].A;
if ( visited[nextcity] == TRUE )
{
nextcity = neighbors[curcity].B;
}
}
else
{
/* Search for a degree 1 unvisited city */
nextcity = neighbors[curcity].A;
if ( visited[nextcity] == TRUE )
{
/* Search for a j unvisited degree 1 city */
while ( top > 0 )
{
top--;
if ( !visited[stack[top]] )
break;
}
if ( top >= 0 )
nextcity = stack[top];
}
}
/* Now j is a valid city to visit next */
curcity = nextcity;
outcycle[i] = curcity;
visited[curcity] = TRUE;
}
#ifdef VERBOSE
for ( i = 0; i < ncount; i++ )
fprintf ( outfile, "Tour[%3d]: %3d\n", i, outcycle[i] );
#endif
return;
}
int
ap_bbtsp ( int ncount, int *tour, int **weights, int **status,
intpair_t * neighbors, int *stack,
int *outcycle, int *degree, int *otherEnd, smalledge_t * edges )
{
int mincost, found_cost;
int num_genes;
int i;
num_genes = ncount / 2;
mincost = LARGENUM * ncount;
#ifdef VERBOSE
fprintf ( outfile, "Running bbtsp on %4d cities... \n", ncount );
fflush ( outfile );
#endif
/* uses positive/negative indexing and so position 0 in arrays
is always wasted */
ap_tsp_dfs ( ncount, mincost, &found_cost, degree, weights, status,
neighbors, stack, outcycle, otherEnd, edges );
/* Fill tour only if better than initial */
if ( found_cost < mincost )
{
#ifdef VERBOSE
fprintf ( outfile, "better tour -- found_cost=%5d, mincost=%5d\n",
found_cost, mincost );
fflush ( outfile );
#endif
if ( outcycle[0] != -outcycle[1] )
{
for ( i = 0; i < num_genes; i++ )
{
tour[i] = outcycle[2 * i];
#ifdef VERBOSE
fprintf ( outfile, "tour[%3d]=%3d\n", i, tour[i] );
fflush ( outfile );
#endif
}
}
else
{
for ( i = 0; i < num_genes; i++ )
{
tour[i] = outcycle[( 2 * i + 1 ) % ncount];
#ifdef VERBOSE
fprintf ( outfile, "tour[%3d]=%3d\n", i, tour[i] );
fflush ( outfile );
#endif
}
}
mincost = found_cost;
}
return mincost;
}
int
ap_coalestsp ( int ncount, int *tour, int **weights,
intpair_t * neighbors, int *stack,
int *outcycle, int *degree, int *otherEnd,
smalledge_t * edges )
{
/* uses coalesced simple path heuristic to build tour */
/* ncount is effectively a constant */
/* outcycle is the returned tour */
/* pointers to arrays adj_list, degree, neighbors, and otherEnd are
passed in shifted to the middle to allow negative indexing */
/* pointers to arrays outcycle, and edges are not shifted */
int num_genes;
int i, j, top;
int countm3, countm2, countm1, count0, count1, count2, countL;
smalledge_t *edgesm3, *edgesm2, *edgesm1, *edges0, *edges1, *edges2,
*edgesL;
smalledge_t *newedge;
int score, picked;
int numedges, negEdges;
int otherEndI, otherEndJ;
int *visited;
int curcity, nextcity;
num_genes = ncount / 2;
#ifdef VERBOSE
fprintf ( outfile, "Running ap_coalestsp on %4d cities... \n", ncount );
fflush ( outfile );
#endif
/* uses positive/negative indexing and so position 0 in arrays
is always wasted */
/* prepare a sorted list of edges (in increasing order of cost) */
/* use distribution sort -- here ad hoc, since we only have 7 values:
-3, -2, -1, 0, 1, 2, and L = -largevalue */
/* could just use an array of pointers since adj. lists are sorted... */
/* tally values */
countL = countm3 = countm2 = countm1 = count0 = count1 = count2 = 0;
for ( i = 0; i < ncount; i++ )
for ( j = i + 1; j < ncount; j++ )
{
switch ( weights[i][j] )
{
case -3:
countm3++;
break;
case -2:
countm2++;
break;
case -1:
countm1++;
break;
case 0:
count0++;
break;
case 1:
count1++;
break;
case 2:
count2++;
break;
case 3:
break; /* don't care about these, don't count them */
default:
countL++;
break;
}
}
numedges =
countm3 + countm2 + countm1 + count0 + count1 + count2 + countL;
negEdges = countL;
edgesL = edges;
edgesm3 = edgesL + countL;
edgesm2 = edgesm3 + countm3;
edgesm1 = edgesm2 + countm2;
edges0 = edgesm1 + countm1;
edges1 = edges0 + count0;
edges2 = edges1 + count1;
for ( i = 0; i < ncount; i++ )
for ( j = i + 1; j < ncount; j++ )
{
switch ( weights[i][j] )
{
case -3:
edgesm3->I = i;
edgesm3->J = j;
edgesm3++;
break;
case -2:
edgesm2->I = i;
edgesm2->J = j;
edgesm2++;
break;
case -1:
edgesm1->I = i;
edgesm1->J = j;
edgesm1++;
break;
case 0:
edges0->I = i;
edges0->J = j;
edges0++;
break;
case 1:
edges1->I = i;
edges1->J = j;
edges1++;
break;
case 2:
edges2->I = i;
edges2->J = j;
edges2++;
break;
case 3:
break; /* don't register */
default:
edgesL->I = i;
edgesL->J = j;
edgesL++;
break;
}
}
#ifdef DEBUG
for ( i = 0; i < numedges; i++ )
fprintf ( outfile, "Edge[%3d]: (%4d, %4d), wt: %7d\n",
i, edges[i].I, edges[i].J,
weights[edges[i].I][edges[i].J] );
fprintf ( outfile, "\n" );
fflush ( outfile );
#endif
/* initialize degree to all 1s, to reflect the fact that
the (g,-g) edges are forcibly included */
for ( i = -num_genes; i < 0; i++ )
degree[i] = 1;
degree[0] = 0; /* thus will never be used */
for ( i = 1; i <= num_genes; i++ )
degree[i] = 1;
/* initialize global variables and structures */
score = 0; /* total value of edges picked so far */
picked = 0; /* number of edges picked so far */
newedge = edges;
/* Initialize otherEnd[city] to itself */
for ( i = -num_genes; i <= num_genes; i++ )
otherEnd[i] = i;
/* initially include -Z weight edges (g,-g) */
while ( weights[newedge->I][newedge->J] < -3 )
{
stack[picked] = picked;
/* decode values of indices */
i = newedge->I;
if ( i < num_genes )
i = -( i + 1 );
else
i = i + 1 - num_genes;
j = newedge->J;
if ( j < num_genes )
j = -( j + 1 );
else
j = j + 1 - num_genes;
otherEnd[i] = j;
otherEnd[j] = i;
neighbors[i].A = j;
neighbors[j].A = i;
score += weights[newedge->I][newedge->J];
picked++;
newedge++;
}
#ifdef DEBUG
if ( picked != negEdges )
fprintf ( outfile, "ERROR: picked: %d negEdges: %d\n", picked,
negEdges );
fflush ( outfile );
#endif
/* initial best solution is actually empty (beyond g/-g edges */
for ( i = negEdges; i < ncount; i++ )
stack[i] = NOEDGE; /* no such edge */
/* greedily include all cheap edges we can */
while ( ( picked < ncount ) && ( newedge < ( edges + numedges ) ) )
{
/* decode values of indices */
i = newedge->I;
if ( i < num_genes )
i = -( i + 1 );
else
i = i + 1 - num_genes;
j = newedge->J;
if ( j < num_genes )
j = -( j + 1 );
else
j = j + 1 - num_genes;
#ifdef DEBUG
fprintf ( outfile, "checking edge (%3d,%3d) for inclusion\n",
newedge->I, newedge->J );
fflush ( outfile );
#endif
/* attempt to include newedge */
if ( ( degree[i] <= 1 ) && ( degree[j] <= 1 ) &&
( ( otherEnd[i] != j ) || ( picked == ncount - 1 ) ) )
{
#ifdef DEBUG
fprintf ( outfile, "OK, pick it\n" );
fflush ( outfile );
#endif
stack[picked] = newedge - edges; /* actual index in edges array */
score += weights[newedge->I][newedge->J];
otherEndI = otherEnd[i];
otherEndJ = otherEnd[j];
otherEnd[otherEndI] = otherEndJ;
otherEnd[otherEndJ] = otherEndI;
neighbors[i].B = j;
neighbors[j].B = i;
degree[i] += 1;
degree[j] += 1;
picked++;
}
newedge++;
}
stack[picked] = -1;
/* any missing edges are from the expensive pool */
score += 3 * ( ncount - picked );
/* stack at this point is a stack of edges of cost 0, 1, or 2
in the optimal solution. Complete it into a full tour by using
whatever cost 3 edges are needed and store results in outcycle. */
visited = otherEnd; /* reuse existing space */
for ( i = -num_genes; i < 0; i++ )
visited[i] = FALSE;
visited[0] = TRUE;
for ( i = 1; i <= num_genes; i++ )
visited[i] = FALSE;
for ( i = 0; i < ncount; i++ )
outcycle[i] = stack[i];
/* push on a stack cities of degree 1, if any */
top = 0;
for ( i = -num_genes; i <= num_genes; i++ )
{
if ( degree[i] == 1 )
{
stack[top] = i;
top++;
}
}
#ifdef DEBUG
fprintf ( outfile, "converting tour: neighbors computed are:\n" );
for ( i = -num_genes; i <= num_genes; i++ )
fprintf ( outfile, "neighbors[%3d].A=%3d, neighbors[%3d].B=%3d\n", i,
neighbors[i].A, i, neighbors[i].B );
fflush ( outfile );
#endif
/* Find the starting city, either a city of degree 1
or any city if all are degree 2 */
if ( top > 0 )
{
top--;
curcity = stack[top];
}
else
{
curcity = 1; /* not entirely arbitrary -- must match decode
at end of bbtsp */
}
/* Note that city 0 may pick either of two edges, but this is okay */
outcycle[0] = curcity;
visited[curcity] = TRUE;
for ( i = 1; i < ncount; i++ )
{
if ( degree[curcity] == 2 )
{
/* Use one of the unvisited neighbors */
nextcity = neighbors[curcity].A;
if ( visited[nextcity] == TRUE )
{
nextcity = neighbors[curcity].B;
}
}
else
{
/* Search for a degree 1 unvisited city */
nextcity = neighbors[curcity].A;
if ( visited[nextcity] == TRUE )
{
/* Search for a j unvisited degree 1 city */
while ( top > 0 )
{
top--;
if ( !visited[stack[top]] )
break;
}
if ( top >= 0 )
nextcity = stack[top];
}
}
/* Now j is a valid city to visit next */
curcity = nextcity;
outcycle[i] = curcity;
visited[curcity] = TRUE;
}
#ifdef VERBOSE