void annealing(TSP *tsp)
{
Path p;
int i, j, pathchg;
int numOnPath, numNotOnPath;
DTYPE pathlen;
int n = tsp->n;
double energyChange, T;
pathlen = pathLength (tsp);
for (T = T_INIT; T > FINAL_T; T *= COOLING) /* annealing schedule */
{
pathchg = 0;
for (j = 0; j < TRIES_PER_T; j++)
{
do {
p[0] = unifRand (n);
p[1] = unifRand (n);
/* non-empty path */
if (p[0] == p[1]) p[1] = MOD(p[0]+1,n);
numOnPath = MOD(p[1]-p[0],n) + 1;
numNotOnPath = n - numOnPath;
} while (numOnPath < 2 || numNotOnPath < 2); /* non-empty path */
if (RANDOM() % 2) /* threeWay */
{
do {
p[2] = MOD(unifRand (numNotOnPath)+p[1]+1,n);
} while (p[0] == MOD(p[2]+1,n)); /* avoids a non-change */
energyChange = getThreeWayCost (tsp, p);
if (energyChange < 0 || RREAL < exp(-energyChange/T) )
{
pathchg++;
pathlen += energyChange;
doThreeWay (tsp, p);
}
}
else /* path Reverse */
{
energyChange = getReverseCost (tsp, p);
if (energyChange < 0 || RREAL < exp(-energyChange/T))
{
pathchg++;
pathlen += energyChange;
doReverse(tsp, p);
}
}
// if the new length is better than best then save it as best
if (pathlen < tsp->bestlen) {
tsp->bestlen = pathlen;
for (i=0; i<tsp->n; i++) tsp->border[i] = tsp->iorder[i];
}
if (pathchg > IMPROVED_PATH_PER_T) break; /* finish early */
}
DBG("T:%f L:%f B:%f C:%d", T, pathlen, tsp->bestlen, pathchg);
if (pathchg == 0) break; /* if no change then quit */
}
}
void
TSP::annealing() {
Path p;
size_t numOnPath, numNotOnPath;
double pathCost(dist.pathCost(iorder));
const double T_INIT = 100.0;
const double FINAL_T = 0.1;
const double COOLING = 0.9; /* to lower down T (< 1) */
const size_t TRIES_PER_T(500 * n);
const size_t IMPROVED_PATH_PER_T = 60 * n;
/* annealing schedule */
for (double T = T_INIT; FINAL_T < T; T *= COOLING) {
size_t pathchg = 0;
for (size_t j = 0; j < TRIES_PER_T; j++) {
do {
p[0] = rand(n);
p[1] = rand(n);
/* non-empty path */
if (p[0] == p[1])
p[1] = MOD(p[0] + 1, n);
numOnPath = MOD(p[1] - p[0], n) + 1;
numNotOnPath = n - numOnPath;
} while (numOnPath < 2 || numNotOnPath < 2); /* non-empty path */
if (rand(2)) {
/* threeWay */
do {
p[2] = MOD(rand(numNotOnPath) + p[1] + 1, n);
} while (p[0] == MOD(p[2] + 1, n)); /* avoids a non-change */
auto energyChange = getThreeWayCost(p);
// if (energyChange < 0 || RREAL < exp(-energyChange / T) )
if (energyChange < 0 || std::rand() < exp(-energyChange / static_cast<double>(T)) ) {
pathchg++;
pathCost += energyChange;
doThreeWay(p);
}
} else {
/* path Reverse */
auto energyChange = getReverseCost(p);
if (energyChange < 0 || std::rand() < exp(-energyChange / static_cast<double>(T)) ) {
pathchg++;
pathCost += energyChange;
doReverse(p);
}
}
// if the new length is better than best then save it as best
update(iorder);
#if 0
if (pathlen < tsp->bestlen) {
tsp->bestlen = pathlen;
for (i=0; i<tsp->n; i++) tsp->border[i] = tsp->iorder[i];
}
#endif
if (pathchg > IMPROVED_PATH_PER_T) break; /* finish early */
}
// PGR_DBG("T:%f L:%f B:%f C:%d", T, pathlen, tsp->bestlen, pathchg);
if (pathchg == 0) break; /* if no change then quit */
}
}
