double pareto(double a, double b)
{
double y1;
double y2;
double y3;
y1 = 1 - randfrac();
y2 = -(1/b)*(log(y1));
y3 = pow(a, exp(y2));
return y3;
}
Graph *
geo(long seed, geo_parms *pp)
{
double p,d,L,radius,r;
u_char *occ;
register int scale;
unsigned nbytes, index, x, y;
u_long units,pertrange;
int mallocd;
register i,j;
Graph *G;
Vertex *up,*vp;
char namestr[128];
gb_trouble_code = 0;
if (seed) /* zero seed means "already init'd */
gb_init_rand(seed);
scale = pp->scale;
L = sqrt(2.0) * scale;
gb_trouble_code = 0;
if ((pp->alpha <= 0.0) || (pp->alpha > 1.0)) gb_trouble_code=bad_specs+1;
if (pp->gamma < 0.0) gb_trouble_code=bad_specs+GEO_TRBL;
if (pp->beta < 0.0) gb_trouble_code=bad_specs+GEO_TRBL;
if (pp->n > (scale * scale)) gb_trouble_code=bad_specs+GEO_TRBL;
if (gb_trouble_code)
return NULL;
radius = pp->gamma * L; /* comes in as a fraction of diagonal */
#define posn(x,y) ((x)*scale)+(y)
#define bitset(v,i) (v[(i)/NBBY]&(1<<((i)%NBBY)))
#define setbit(v,i) v[(i)/NBBY] |= (1<<((i)%NBBY))
/* create a new graph structure */
if ((G=gb_new_graph(pp->n)) == NULL)
return NULL;
nbytes = ((scale*scale)%NBBY ? (scale*scale/NBBY)+1 : (scale*scale)/NBBY);
if (nbytes < STACKMAX) { /* small amount - just do it in the stack */
occ = (u_char *) alloca(nbytes);
mallocd = 0;
} else {
occ = (u_char *) malloc(nbytes);
mallocd = 1;
}
for (i=0; i<nbytes; i++) occ[i] = 0;
/* place each of n points in the plane */
for (i=0,vp = G->vertices; i<pp->n; i++,vp++) {
sprintf(namestr,"%d",i); /* name is just node number */
vp->name = gb_save_string(namestr);
do {
vp->xpos = gb_next_rand()%scale; /* position: 0..scale-1 */
vp->ypos = gb_next_rand()%scale; /* position: 0..scale-1 */
index = posn(vp->xpos,vp->ypos);
} while (bitset(occ,index));
setbit(occ,index);
}
/* Now go back and add the edges */
for (i=0,up = G->vertices; i<(pp->n)-1; i++,up++)
for (j=i+1, vp = &G->vertices[i+1]; j<pp->n; j++,vp++) {
d = distance(up,vp);
switch (pp->method) {
case RG2: /* Waxman's */
d = randfrac()*L;
/* fall through */
case RG1: /* Waxman's */
p = pp->alpha * exp(-d/(L*pp->beta));
break;
case RANDOM: /* the classic */
p = pp->alpha;
break;
case EXP:
p = pp->alpha * exp(-d/(L-d));
break;
case DL: /* Doar-Leslie */
p = pp->alpha * (pp->gamma/pp->n) * exp(-d/(L*pp->beta));
break;
case LOC: /* Locality model, two probabilities */
if (d <= radius) p = pp->alpha;
else p = pp->beta;
break;
default:
die("Bad edge method in geo()!");
}
if (randfrac() < p)
gb_new_edge(up,vp,(int)rint(d));
}
/* Fill in the "id" string to say how the graph was created */
G->Gscale = scale;
sprintf(G->id,"geo(%ld,", seed);
i = strlen(G->id);
i += printparms(G->id+i,pp);
G->id[i] = ')';
G->id[i+1] = (char) 0;
strcpy(G->util_types,GEO_UTIL);
/* clean up */
if (mallocd) free(occ);
return G;
}
