void
median (
struct vtx_data **graph, /* data structure with vertex weights */
double *vals, /* values of which to find median */
int nvtxs, /* number of values I own */
int *active, /* space for list of nvtxs ints */
double *goal, /* desired sizes for sets */
int using_vwgts, /* are vertex weights being used? */
int *sets /* set each vertex gets assigned to */
)
{
double *vptr; /* loops through vals array */
double val; /* value in vals array */
double maxval; /* largest active value */
double minval; /* smallest active value */
double guess; /* approximate median value */
double nearup; /* lowest guy above guess */
double neardown; /* highest guy below guess */
double whigh; /* total weight of values above maxval */
double wlow; /* total weight of values below minval */
double wabove; /* total weight of active values above guess */
double wbelow; /* total weight of active values below guess */
double wexact; /* weight of vertices exactly at guess */
double lweight; /* desired weight of lower values in set */
double uweight; /* desired weight of upper values in set */
double frac; /* fraction of values I want less than guess */
int *aptr; /* loops through active array */
int *aptr2; /* helps update active array */
int myactive; /* number of active values I own */
double wfree; /* weight of vtxs not yet divided */
int removed; /* number of my values eliminated */
/*int npass = 0;*/ /* counts passes required to find median */
int done; /* check for termination criteria */
int vtx; /* vertex being considered */
int i; /* loop counters */
/* Initialize. */
/* Determine the desired weight sums for the two different sets. */
lweight = goal[0];
uweight = goal[1];
myactive = nvtxs;
whigh = wlow = 0;
/* Find largest and smallest values in vector, and construct active list. */
vptr = vals;
aptr = active;
minval = maxval = *(++vptr);
*aptr++ = 1;
for (i = 2; i <= nvtxs; i++) {
*aptr++ = i;
val = *(++vptr);
if (val > maxval)
maxval = val;
if (val < minval)
minval = val;
}
/* Loop until all sets are partitioned correctly. */
done = FALSE;
while (!done) {
/*npass++;*/
/* Select a potential dividing value. */
/* Currently, this assumes a linear distribution. */
wfree = lweight + uweight - (wlow + whigh);
frac = (lweight - wlow) / wfree;
/* Overshoot a bit to try to cut into largest set. */
frac = .5 * (frac + .5);
guess = minval + frac * (maxval - minval);
/* Now count the guys above and below this guess. */
/* Also find nearest values on either side of guess. */
wabove = wbelow = wexact = 0;
nearup = maxval;
neardown = minval;
aptr = active;
for (i = 0; i < myactive; i++) {
vtx = *aptr++;
val = vals[vtx];
if (val > guess) {
if (using_vwgts)
wabove += graph[vtx]->vwgt;
else
wabove++;
if (val < nearup)
nearup = val;
}
else if (val < guess) {
if (using_vwgts)
wbelow += graph[vtx]->vwgt;
else
wbelow++;
if (val > neardown)
neardown = val;
}
else {
if (using_vwgts)
wexact += graph[vtx]->vwgt;
else
wexact++;
}
}
/* Select a half to discard. */
/* And remove discarded vertices from active list. */
removed = 0;
if (wlow + wbelow - lweight > whigh + wabove - uweight &&
whigh + wabove + wexact < uweight ) {
/* Discard upper set. */
whigh += wabove + wexact;
maxval = neardown;
done = FALSE;
aptr = aptr2 = active;
for (i = 0; i < myactive; i++) {
if (vals[*aptr] >= guess) {
++removed;
}
else
*aptr2++ = *aptr;
aptr++;
}
myactive -= removed;
if (myactive == 0) done = TRUE;
}
else if ( whigh + wabove - uweight > wlow + wbelow - lweight &&
wlow + wbelow + wexact < lweight ) {
/* Discard lower set. */
wlow += wbelow + wexact;
minval = nearup;
done = FALSE;
aptr = aptr2 = active;
for (i = 0; i < myactive; i++) {
if (vals[*aptr] <= guess) {
++removed;
}
else
*aptr2++ = *aptr;
aptr++;
}
myactive -= removed;
if (myactive == 0) done = TRUE;
}
else { /* Perfect partition! */
wlow += wbelow;
whigh += wabove;
done = TRUE;
}
/* Check for alternate termination criteria. */
if (!done && maxval == minval) {
guess = maxval;
done = TRUE;
}
}
median_assign(graph, vals, nvtxs, goal, using_vwgts, sets, wlow, whigh, guess);
}
void
mapper (
struct vtx_data **graph, /* data structure with vertex weights */
double **xvecs, /* continuous indicator vectors */
int nvtxs, /* number of vtxs in graph */
int *active, /* space for nmyvals ints */
int *sets, /* returned processor assignment for my vtxs */
int ndims, /* number of dimensions being divided into */
int cube_or_mesh, /* 0 => hypercube, d => d-dimensional mesh */
int nsets, /* number of sets to divide into */
int mediantype, /* type of eigenvector partitioning to use */
double *goal, /* desired set sizes */
int vwgt_max /* largest vertex weight */
)
{
double temp_goal[2]; /* combined set goals if using option 1. */
double wbelow; /* weight of vertices with negative values */
double wabove; /* weight of vertices with positive values */
int *temp_sets; /* sets vertices get assigned to */
int vweight; /* weight of a vertex */
int using_vwgts; /* are vertex weights being used? */
int bits; /* bits for assigning set numbers */
int i, j; /* loop counters */
void median(), rec_median_k(), rec_median_1(), median_assign();
void map2d(), map3d();
/* NOTE: THIS EXPECTS XVECS, NOT YVECS! */
using_vwgts = (vwgt_max != 1);
if (ndims == 1 && mediantype == 1)
mediantype = 3; /* simpler call than normal option 1. */
if (mediantype == 0) { /* Divide at zero instead of median. */
bits = 1;
temp_sets = smalloc((nvtxs + 1) * sizeof(int));
for (j = 1; j <= nvtxs; j++)
sets[j] = 0;
for (i = 1; i <= ndims; i++) {
temp_goal[0] = temp_goal[1] = 0;
for (j = 0; j < (1 << ndims); j++) {
if (bits & j)
temp_goal[1] += goal[j];
else
temp_goal[0] += goal[j];
}
bits <<= 1;
wbelow = wabove = 0;
vweight = 1;
for (j = 1; j <= nvtxs; j++) {
if (using_vwgts)
vweight = graph[j]->vwgt;
if (xvecs[i][j] < 0)
wbelow += vweight;
else if (xvecs[i][j] > 0)
wabove += vweight;
}
median_assign(graph, xvecs[i], nvtxs, temp_goal, using_vwgts, temp_sets,
wbelow, wabove, (double) 0.0);
for (j = 1; j <= nvtxs; j++)
sets[j] = (sets[j] << 1) + temp_sets[j];
}
}
else if (mediantype == 1) { /* Divide using min-cost assignment. */
if (ndims == 2)
map2d(graph, xvecs, nvtxs, sets, goal, vwgt_max);
else if (ndims == 3)
map3d(graph, xvecs, nvtxs, sets, goal, vwgt_max);
}
else if (mediantype == 2) { /* Divide recursively using medians. */
rec_median_k(graph, xvecs, nvtxs, active, ndims, cube_or_mesh, goal,
using_vwgts, sets);
}
else if (mediantype == 3) { /* Cut with independent medians => unbalanced. */
bits = 1;
temp_sets = smalloc((nvtxs + 1) * sizeof(int));
for (j = 1; j <= nvtxs; j++)
sets[j] = 0;
for (i = 1; i <= ndims; i++) {
temp_goal[0] = temp_goal[1] = 0;
for (j = 0; j < (1 << ndims); j++) {
if (bits & j)
temp_goal[1] += goal[j];
else
temp_goal[0] += goal[j];
}
bits <<= 1;
median(graph, xvecs[i], nvtxs, active, temp_goal, using_vwgts, temp_sets);
for (j = 1; j <= nvtxs; j++)
sets[j] = (sets[j] << 1) + temp_sets[j];
}
sfree(temp_sets);
}
if (mediantype == 4) { /* Stripe the domain. */
rec_median_1(graph, xvecs[1], nvtxs, active, cube_or_mesh, nsets,
goal, using_vwgts, sets, TRUE);
}
}
