void exampleMinHeap()
{
// Use pooling for efficiency, if you don't want to use pooling
// then comment out this line.
pool_minheap(32);
MinHeap* H = newMinHeap(31);
minheap_add(H, 99, "99");
minheap_add(H, 45, "45");
minheap_add(H, 57, "57");
minheap_add(H, 12, "12");
minheap_add(H, 87, "87");
minheap_add(H, 42, "42");
minheap_add(H, 67, "67");
minheap_display(H, 2, &toString);
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
minheap_display(H, 2, &toString);
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
minheap_display(H, 2, &toString);
printf("Update 45 to 91\n");
minheap_update(H, 45, 91);
minheap_set(H, 91, "91");
minheap_display(H, 2, &toString);
printf("Update 91 to 1\n");
minheap_update(H, 91, 1);
minheap_set(H, 1, "1");
minheap_display(H, 2, &toString);
printf("Add 50\n");
minheap_add(H, 50, "50");
minheap_display(H, 2, &toString);
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
minheap_display(H, 2, &toString);
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
printf("Pop: '%s'\n", (char*)minheap_popMin(H));
minheap_display(H, 2, &toString);
minheap_clear(H);
printf("\n");
// Build a much bigger heap
int total = 21;
int keys[] = {0, 23, 3, 6, 41, 17, 21, 8, 9, 68, 2, 1, 34, 29, 38, 11, 15, 16, 45, 65, 39};
char* items[] = {"0", "23", "3", "6", "41", "17", "21", "8", "9", "68", "2", "1", "34", "29", "38", "11", "15", "16", "45", "65", "39"};
while (--total >= 0)
minheap_add(H, keys[total], items[total]);
minheap_display(H, 2, &toString);
printf("Popping.. ");
while (!minheap_isEmpty(H))
printf("%s ", (char*)minheap_popMin(H));
printf("\n");
minheap_free(H);
// If you're not using pooling this can be commented out. This will
// free all pooled nodes from memory. Always call this at the end
// of using any List.
unpool_minheap();
}
/**
To get the effective area, we have to check what area a point results in when all smaller areas are eliminated
*/
static void tune_areas(EFFECTIVE_AREAS *ea, int avoid_collaps, int set_area, double trshld)
{
LWDEBUG(2, "Entered tune_areas");
const double *P1;
const double *P2;
const double *P3;
double area;
int go_on=1;
double check_order_min_area = 0;
int npoints=ea->inpts->npoints;
int i;
int current, before_current, after_current;
MINHEAP tree = initiate_minheap(npoints);
int is3d = FLAGS_GET_Z(ea->inpts->flags);
/*Add all keys (index in initial_arealist) into minheap array*/
for (i=0;i<npoints;i++)
{
tree.key_array[i]=ea->initial_arealist+i;
LWDEBUGF(2, "add nr %d, with area %lf, and %lf",i,ea->initial_arealist[i].area, tree.key_array[i]->area );
}
tree.usedSize=npoints;
/*order the keys by area, small to big*/
qsort(tree.key_array, npoints, sizeof(void*), cmpfunc);
/*We have to put references to our tree in our point-list*/
for (i=0;i<npoints;i++)
{
((areanode*) tree.key_array[i])->treeindex=i;
LWDEBUGF(4,"Check ordering qsort gives, area=%lf and belong to point %d",((areanode*) tree.key_array[i])->area, tree.key_array[i]-ea->initial_arealist);
}
/*Ok, now we have a minHeap, just need to keep it*/
/*for (i=0;i<npoints-1;i++)*/
i=0;
while (go_on)
{
/*Get a reference to the point with the currently smallest effective area*/
current=minheap_pop(&tree, ea->initial_arealist)-ea->initial_arealist;
/*We have found the smallest area. That is the resulting effective area for the "current" point*/
if (i<npoints-avoid_collaps)
ea->res_arealist[current]=ea->initial_arealist[current].area;
else
ea->res_arealist[current]=FLT_MAX;
if(ea->res_arealist[current]<check_order_min_area)
lwerror("Oh no, this is a bug. For some reason the minHeap returned our points in the wrong order. Please file a ticket in PostGIS ticket system, or send a mial at the mailing list.Returned area = %lf, and last area = %lf",ea->res_arealist[current],check_order_min_area);
check_order_min_area=ea->res_arealist[current];
/*The found smallest area point is now regarded as elimnated and we have to recalculate the area the adjacent (ignoring earlier elimnated points) points gives*/
/*FInd point before and after*/
before_current=ea->initial_arealist[current].prev;
after_current=ea->initial_arealist[current].next;
P2= (double*)getPoint_internal(ea->inpts, before_current);
P3= (double*)getPoint_internal(ea->inpts, after_current);
/*Check if point before current point is the first in the point array. */
if(before_current>0)
{
P1= (double*)getPoint_internal(ea->inpts, ea->initial_arealist[before_current].prev);
if(is3d)
area=triarea3d(P1, P2, P3);
else
area=triarea2d(P1, P2, P3);
ea->initial_arealist[before_current].area = FP_MAX(area,ea->res_arealist[current]);
minheap_update(&tree, ea->initial_arealist, ea->initial_arealist[before_current].treeindex);
}
if(after_current<npoints-1)/*Check if point after current point is the last in the point array. */
{
P1=P2;
P2=P3;
P3= (double*)getPoint_internal(ea->inpts, ea->initial_arealist[after_current].next);
if(is3d)
area=triarea3d(P1, P2, P3);
else
area=triarea2d(P1, P2, P3);
ea->initial_arealist[after_current].area = FP_MAX(area,ea->res_arealist[current]);
minheap_update(&tree, ea->initial_arealist, ea->initial_arealist[after_current].treeindex);
}
/*rearrange the nodes so the eliminated point will be ingored on the next run*/
ea->initial_arealist[before_current].next = ea->initial_arealist[current].next;
ea->initial_arealist[after_current].prev = ea->initial_arealist[current].prev;
/*Check if we are finnished*/
if((!set_area && ea->res_arealist[current]>trshld) || (ea->initial_arealist[0].next==(npoints-1)))
go_on=0;
i++;
};
destroy_minheap(tree);
return;
}
