Apply node sorting before descent to CIRC_NODE trees for

faster calculation of geography distances.
Closes #4010

git-svn-id: http://svn.osgeo.org/postgis/trunk@16371 b70326c6-7e19-0410-871a-916f4a2858ee

diff --git a/liblwgeom/lwgeodetic_tree.c b/liblwgeom/lwgeodetic_tree.c
index 80a838d12b520706bad6e38d4e7cac11b0f49852..24c66762da16223e5102418242f876950a891020 100644 (file)
--- a/liblwgeom/lwgeodetic_tree.c
+++ b/liblwgeom/lwgeodetic_tree.c
@@ -601,6 +601,51 @@ circ_tree_distance_tree(const CIRC_NODE* n1, const CIRC_NODE* n2, const SPHEROID
        }
 }
 
+
+/***********************************************************************
+* Internal node sorting routine to make distance calculations faster?
+*/
+
+struct sort_node {
+       CIRC_NODE *node;
+       double d;
+};
+
+static int
+circ_nodes_sort_cmp(const void *a, const void *b)
+{
+       struct sort_node *node_a = (struct sort_node *)(a);
+       struct sort_node *node_b = (struct sort_node *)(b);
+       if (node_a->d < node_b->d) return -1;
+       else if (node_a->d > node_b->d) return 1;
+       else return 0;
+}
+
+static void
+circ_internal_nodes_sort(CIRC_NODE **nodes, uint32_t num_nodes, const CIRC_NODE *target_node)
+{
+       int i;
+       struct sort_node sort_nodes[CIRC_NODE_SIZE];
+
+       /* Copy incoming nodes into sorting array and calculate */
+       /* distance to the target node */
+       for (i = 0; i < num_nodes; i++)
+       {
+               sort_nodes[i].node = nodes[i];
+               sort_nodes[i].d = sphere_distance(&(nodes[i]->center), &(target_node->center));
+       }
+
+       /* Sort the nodes and copy the result back into the input array */
+       qsort(sort_nodes, num_nodes, sizeof(struct sort_node), circ_nodes_sort_cmp);
+       for (i = 0; i < num_nodes; i++)
+       {
+               nodes[i] = sort_nodes[i].node;
+       }
+       return;
+}
+
+/***********************************************************************/
+
 static double
 circ_tree_distance_tree_internal(const CIRC_NODE* n1, const CIRC_NODE* n2, double threshold, double* min_dist, double* max_dist, GEOGRAPHIC_POINT* closest1, GEOGRAPHIC_POINT* closest2)
 {
@@ -746,6 +791,7 @@ circ_tree_distance_tree_internal(const CIRC_NODE* n1, const CIRC_NODE* n2, doubl
                /* tests above. */
                if ( n1->geom_type && lwtype_is_collection(n1->geom_type) )
                {
+                       circ_internal_nodes_sort(n1->nodes, n1->num_nodes, n2);
                        for ( i = 0; i < n1->num_nodes; i++ )
                        {
                                d = circ_tree_distance_tree_internal(n1->nodes[i], n2, threshold, min_dist, max_dist, closest1, closest2);
@@ -754,6 +800,7 @@ circ_tree_distance_tree_internal(const CIRC_NODE* n1, const CIRC_NODE* n2, doubl
                }
                else if ( n2->geom_type && lwtype_is_collection(n2->geom_type) )
                {
+                       circ_internal_nodes_sort(n2->nodes, n2->num_nodes, n1);
                        for ( i = 0; i < n2->num_nodes; i++ )
                        {
                                d = circ_tree_distance_tree_internal(n1, n2->nodes[i], threshold, min_dist, max_dist, closest1, closest2);
@@ -762,6 +809,7 @@ circ_tree_distance_tree_internal(const CIRC_NODE* n1, const CIRC_NODE* n2, doubl
                }
                else if ( ! circ_node_is_leaf(n1) )
                {
+                       circ_internal_nodes_sort(n1->nodes, n1->num_nodes, n2);
                        for ( i = 0; i < n1->num_nodes; i++ )
                        {
                                d = circ_tree_distance_tree_internal(n1->nodes[i], n2, threshold, min_dist, max_dist, closest1, closest2);
@@ -770,6 +818,7 @@ circ_tree_distance_tree_internal(const CIRC_NODE* n1, const CIRC_NODE* n2, doubl
                }
                else if ( ! circ_node_is_leaf(n2) )
                {
+                       circ_internal_nodes_sort(n2->nodes, n2->num_nodes, n1);
                        for ( i = 0; i < n2->num_nodes; i++ )
                        {
                                d = circ_tree_distance_tree_internal(n1, n2->nodes[i], threshold, min_dist, max_dist, closest1, closest2);

diff --git a/liblwgeom/lwgeodetic_tree.h b/liblwgeom/lwgeodetic_tree.h
index 53ec0b16a2ca52e635af54fa00df0a1ee8722c01..e9cefee0f16925ee15f1898cfc9b015242388c26 100644 (file)
--- a/liblwgeom/lwgeodetic_tree.h
+++ b/liblwgeom/lwgeodetic_tree.h
@@ -41,6 +41,7 @@ typedef struct circ_node
        struct circ_node** nodes;
        int edge_num;
        uint32_t geom_type;
+       double d;
        POINT2D pt_outside;
        POINT2D* p1;
        POINT2D* p2;