blockpath.c

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/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
#include        <circogen/blockpath.h>
#include        <circogen/circular.h>
#include        <circogen/edgelist.h>
#include        <stddef.h>
#include        <stdbool.h>
#include        <stdint.h>
#include        <util/agxbuf.h>
#include        <util/alloc.h>
#include        <util/list.h>
 
/* The code below lays out a single block on a circle.
 */
 
/* We use the unused fields order and to_orig in cloned nodes and edges */
#define ORIGE(e)  (ED_to_orig(e))
 
/* clone_graph:
 * Create two copies of the argument graph
 * One is a subgraph, the other is an actual copy since we will be
 * adding edges to it.
 *
 * @param state Context containing a counter to use for graph copy naming
 */
static Agraph_t *clone_graph(Agraph_t *ing, Agraph_t **xg, circ_state *state) {
    Agraph_t *clone;
    Agraph_t *xclone;
    Agnode_t *n;
    Agnode_t *xn;
    Agnode_t *xh;
    Agedge_t *e;
    Agedge_t *xe;
    agxbuf gname = {0};
 
    agxbprint(&gname, "_clone_%d", state->graphCopyCount++);
    clone = agsubg(ing, agxbuse(&gname), 1);
    agbindrec(clone, "Agraphinfo_t", sizeof(Agraphinfo_t), true);       //node custom data
    agxbprint(&gname, "_clone_%d", state->graphCopyCount++);
    xclone = agopen(agxbuse(&gname), ing->desc, NULL);
    agxbfree(&gname);
    for (n = agfstnode(ing); n; n = agnxtnode(ing, n)) {
        agsubnode(clone,n,1);
        xn = agnode(xclone, agnameof(n),1);
        agbindrec(xn, "Agnodeinfo_t", sizeof(Agnodeinfo_t), true);      //node custom data
        CLONE(n) = xn;
    }
 
    for (n = agfstnode(ing); n; n = agnxtnode(ing, n)) {
        xn = CLONE(n);
        for (e = agfstout(ing, n); e; e = agnxtout(ing, e)) {
            agsubedge(clone,e,1);
            xh = CLONE(aghead(e));
            xe = agedge(xclone, xn, xh, NULL, 1);
            agbindrec(xe, "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);  //node custom data
            ORIGE(xe) = e;
            DEGREE(xn) += 1;
            DEGREE(xh) += 1;
        }
    }
    *xg = xclone;
    return clone;
}
 
typedef LIST(Agnode_t *) deglist_t;
 
static int cmpDegree(const void *x, const void *y) {
  Agnode_t *const *a = x;
  Agnode_t *const *b = y;
  if (DEGREE(*a) < DEGREE(*b)) {
    return 1;
  }
  if (DEGREE(*a) > DEGREE(*b)) {
    return -1;
  }
  return 0;
}
 
static deglist_t getList(Agraph_t *g) {
    deglist_t dl = {0};
    Agnode_t *n;
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        LIST_APPEND(&dl, n);
    }
    LIST_SORT(&dl, cmpDegree);
    return dl;
}
 
static void find_pair_edges(Agraph_t * g, Agnode_t * n, Agraph_t * outg)
{
    int edge_cnt = 0;
 
    const int node_degree = DEGREE(n);
    LIST(Agnode_t *) neighbors_with = {0};
    LIST(Agnode_t *) neighbors_without = {0};
 
    for (Agedge_t *e = agfstedge(g, n); e; e = agnxtedge(g, e, n)) {
        Agnode_t *n1 = aghead(e);
        if (n1 == n)
            n1 = agtail(e);
        bool has_pair_edge = false;
        for (Agedge_t *ep = agfstedge(g, n); ep; ep = agnxtedge(g, ep, n)) {
            if (ep == e)
                continue;
            Agnode_t *n2 = aghead(ep);
            if (n2 == n)
                n2 = agtail(ep);
            Agedge_t *const ex = agfindedge(g, n1, n2);
            if (ex) {
                has_pair_edge = true;
                if ((uintptr_t)n1 < (uintptr_t)n2) { // count edge only once
                    edge_cnt++;
                    if (ORIGE(ex)) {
                        agdelete(outg, ORIGE(ex));
                        ORIGE(ex) = 0;  /* delete only once */
                    }
                }
            }
        }
        if (has_pair_edge) {
            LIST_APPEND(&neighbors_with, n1);
        } else {
            LIST_APPEND(&neighbors_without, n1);
        }
    }
 
    int diff = node_degree - 1 - edge_cnt;
    if (diff > 0) {
        if ((size_t)diff < LIST_SIZE(&neighbors_without)) {
            for (size_t mark = 0; mark + 1 < LIST_SIZE(&neighbors_without); mark += 2) {
                Agnode_t *const tp = LIST_GET(&neighbors_without, mark);
                Agnode_t *const hp = LIST_GET(&neighbors_without, mark + 1);
                agbindrec(agedge(g, tp, hp, NULL, 1), "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);   // edge custom data
                DEGREE(tp)++;
                DEGREE(hp)++;
                diff--;
            }
 
            for (size_t mark = 2; diff > 0; ++mark, --diff) {
                Agnode_t *const tp = LIST_GET(&neighbors_without, 0);
                Agnode_t *const hp = LIST_GET(&neighbors_without, mark);
                agbindrec(agedge(g, tp, hp, NULL, 1), "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);   // edge custom data
                DEGREE(tp)++;
                DEGREE(hp)++;
            }
        }
 
        else if ((size_t)diff == LIST_SIZE(&neighbors_without)) {
            Agnode_t *const tp =
              LIST_IS_EMPTY(&neighbors_with) ? NULL : LIST_GET(&neighbors_with, 0);
            for (size_t mark = 0; mark < LIST_SIZE(&neighbors_without); mark++) {
                Agnode_t *const hp = LIST_GET(&neighbors_without, mark);
                agbindrec(agedge(g, tp, hp, NULL, 1), "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);      //node custom data
                if (tp != NULL) {
                    DEGREE(tp)++;
                }
                DEGREE(hp)++;
            }
        }
    }
 
    LIST_FREE(&neighbors_without);
    LIST_FREE(&neighbors_with);
}
 
static Agraph_t *remove_pair_edges(Agraph_t *ing, circ_state *state) {
    int nodeCount;
    Agraph_t *outg;
    Agraph_t *g;
    Agnode_t *currnode, *adjNode;
    Agedge_t *e;
 
    outg = clone_graph(ing, &g, state);
    nodeCount = agnnodes(g);
    deglist_t dl = getList(g);
 
    for (int counter = 0; counter < nodeCount - 3; ++counter) {
        currnode = LIST_IS_EMPTY(&dl) ? NULL : LIST_POP_BACK(&dl);
 
        /* Remove all adjacent nodes since they have to be reinserted */
        for (e = agfstedge(g, currnode); e; e = agnxtedge(g, e, currnode)) {
            adjNode = aghead(e);
            if (currnode == adjNode)
                adjNode = agtail(e);
            LIST_REMOVE(&dl, adjNode);
        }
 
        find_pair_edges(g, currnode, outg);
 
        for (e = agfstedge(g, currnode); e; e = agnxtedge(g, e, currnode)) {
            adjNode = aghead(e);
            if (currnode == adjNode)
                adjNode = agtail(e);
 
            DEGREE(adjNode)--;
            LIST_APPEND(&dl, adjNode);
        }
        LIST_SORT(&dl, cmpDegree);
 
        agdelete(g, currnode);
    }
 
    agclose(g);
    LIST_FREE(&dl);
    return outg;
}
 
static void
measure_distance(Agnode_t * n, Agnode_t * ancestor, int dist,
                 Agnode_t * change)
{
    Agnode_t *parent;
 
    parent = TPARENT(ancestor);
    if (parent == NULL)
        return;
 
    dist++;
 
    /* check parent to see if it has other leaf paths at greater distance
       than the context node.
       set the path/distance of the leaf at this ancestor node */
 
    if (DISTONE(parent) == 0) {
        LEAFONE(parent) = n;
        DISTONE(parent) = dist;
    } else if (dist > DISTONE(parent)) {
        if (LEAFONE(parent) != change) {
            if (!DISTTWO(parent) || LEAFTWO(parent) != change)
                change = LEAFONE(parent);
            LEAFTWO(parent) = LEAFONE(parent);
            DISTTWO(parent) = DISTONE(parent);
        }
        LEAFONE(parent) = n;
        DISTONE(parent) = dist;
    } else if (dist > DISTTWO(parent)) {
        LEAFTWO(parent) = n;
        DISTTWO(parent) = dist;
        return;
    } else
        return;
 
    measure_distance(n, parent, dist, change);
}
 
static nodelist_t find_longest_path(Agraph_t *tree) {
    Agnode_t *n;
    Agedge_t *e;
    Agnode_t *common = 0;
    int maxlength = 0;
    int length;
 
    if (agnnodes(tree) == 1) {
        nodelist_t beginPath = {0};
        n = agfstnode(tree);
        LIST_APPEND(&beginPath, n);
        SET_ONPATH(n);
        return beginPath;
    }
 
    for (n = agfstnode(tree); n; n = agnxtnode(tree, n)) {
        int count = 0;
        for (e = agfstedge(tree, n); e; e = agnxtedge(tree, e, n)) {
            count++;
        }
        if (count == 1)
            measure_distance(n, n, 0, NULL);
    }
 
    /* find the branch node rooted at the longest path */
    for (n = agfstnode(tree); n; n = agnxtnode(tree, n)) {
        length = DISTONE(n) + DISTTWO(n);
        if (length > maxlength) {
            common = n;
            maxlength = length;
        }
    }
 
    nodelist_t beginPath = {0};
    for (n = LEAFONE(common); n != common; n = TPARENT(n)) {
        LIST_APPEND(&beginPath, n);
        SET_ONPATH(n);
    }
    LIST_APPEND(&beginPath, common);
    SET_ONPATH(common);
 
    if (DISTTWO(common)) {      /* 2nd path might be empty */
        nodelist_t endPath = {0};
        for (n = LEAFTWO(common); n != common; n = TPARENT(n)) {
            LIST_APPEND(&endPath, n);
            SET_ONPATH(n);
        }
        reverseAppend(&beginPath, &endPath);
    }
 
    return beginPath;
}
 
static void dfs(Agraph_t * g, Agnode_t * n, Agraph_t * tree)
{
    Agedge_t *e;
    Agnode_t *neighbor;
 
    SET_VISITED(n);
    for (e = agfstedge(g, n); e; e = agnxtedge(g, e, n)) {
        neighbor = aghead(e);
        if (neighbor == n)
            neighbor = agtail(e);
 
        if (!VISITED(neighbor)) {
            /* add the edge to the dfs tree */
            agsubedge(tree,e,1);
            TPARENT(neighbor) = n;
            dfs(g, neighbor, tree);
        }
    }
}
 
static Agraph_t *spanning_tree(Agraph_t *g, circ_state *state) {
    Agnode_t *n;
    Agraph_t *tree;
    agxbuf gname = {0};
 
    agxbprint(&gname, "_span_%d", state->spanningTreeCount++);
    tree = agsubg(g, agxbuse(&gname), 1);
    agxbfree(&gname);
    agbindrec(tree, "Agraphinfo_t", sizeof(Agraphinfo_t), true);        //node custom data
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        agsubnode(tree,n,1);
        DISTONE(n) = 0;
        DISTTWO(n) = 0;
        UNSET_VISITED(n);
    }
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (!VISITED(n)) {
            TPARENT(n) = NULL;
            dfs(g, n, tree);
        }
    }
 
    return tree;
}
 
static void block_graph(Agraph_t * g, block_t * sn)
{
    Agnode_t *n;
    Agedge_t *e;
    Agraph_t *subg = sn->sub_graph;
 
    for (n = agfstnode(subg); n; n = agnxtnode(subg, n)) {
        for (e = agfstout(g, n); e; e = agnxtout(g, e)) {
            if (BLOCK(aghead(e)) == sn)
                agsubedge(subg,e,1);
        }
    }
}
 
static int count_all_crossings(nodelist_t * list, Agraph_t * subg)
{
    edgelist *openEdgeList = init_edgelist();
    Agnode_t *n;
    Agedge_t *e;
    int crossings = 0;
    int order = 1;
 
    for (n = agfstnode(subg); n; n = agnxtnode(subg, n)) {
        for (e = agfstout(subg, n); e; e = agnxtout(subg, e)) {
            EDGEORDER(e) = 0;
        }
    }
 
    for (size_t item = 0; item < LIST_SIZE(list); ++item) {
        n = LIST_GET(list, item);
 
        for (e = agfstedge(subg, n); e; e = agnxtedge(subg, e, n)) {
            if (EDGEORDER(e) > 0) {
                edgelistitem *eitem;
                Agedge_t *ep;
 
                for (eitem = dtfirst(openEdgeList); eitem;
                     eitem = dtnext(openEdgeList, eitem)) {
                    ep = eitem->edge;
                    if (EDGEORDER(ep) > EDGEORDER(e)) {
                        if (aghead(ep) != n && agtail(ep) != n)
                            crossings++;
                    }
                }
                remove_edge(openEdgeList, e);
            }
        }
 
        for (e = agfstedge(subg, n); e; e = agnxtedge(subg, e, n)) {
            if (EDGEORDER(e) == 0) {
                EDGEORDER(e) = order;
                add_edge(openEdgeList, e);
            }
        }
        order++;
    }
 
    free_edgelist(openEdgeList);
    return crossings;
}
 
#define CROSS_ITER 10
 
/* Attempt to reduce edge crossings by moving nodes.
 * Original crossing count is in cnt; final count is returned there.
 * list is the original list; return the best list found.
 */
static nodelist_t reduce(nodelist_t list, Agraph_t *subg, int *cnt) {
    Agnode_t *curnode;
    Agedge_t *e;
    Agnode_t *neighbor;
    int crossings, j, newCrossings;
 
    crossings = *cnt;
    for (curnode = agfstnode(subg); curnode;
         curnode = agnxtnode(subg, curnode)) {
        /*  move curnode next to its neighbors */
        for (e = agfstedge(subg, curnode); e;
             e = agnxtedge(subg, e, curnode)) {
            neighbor = agtail(e);
            if (neighbor == curnode)
                neighbor = aghead(e);
 
            for (j = 0; j < 2; j++) {
                nodelist_t listCopy;
                LIST_COPY(&listCopy, &list);
                insertNodelist(&list, curnode, neighbor, j);
                newCrossings = count_all_crossings(&list, subg);
                if (newCrossings < crossings) {
                    crossings = newCrossings;
                    LIST_FREE(&listCopy);
                    if (crossings == 0) {
                        *cnt = 0;
                        return list;
                    }
                } else {
                    LIST_FREE(&list);
                    list = listCopy;
                }
            }
        }
    }
    *cnt = crossings;
    return list;
}
 
static nodelist_t reduce_edge_crossings(nodelist_t list, Agraph_t *subg) {
    int i, crossings, origCrossings;
 
    crossings = count_all_crossings(&list, subg);
    if (crossings == 0)
        return list;
 
    for (i = 0; i < CROSS_ITER; i++) {
        origCrossings = crossings;
        list = reduce(list, subg, &crossings);
        /* return if no crossings or no improvement */
        if (origCrossings == crossings || crossings == 0)
            return list;
    }
    return list;
}
 
static double largest_nodesize(nodelist_t * list)
{
    double size = 0;
 
    for (size_t item = 0; item < LIST_SIZE(list); ++item) {
        Agnode_t *n = ORIGN(LIST_GET(list, item));
        if (ND_width(n) > size)
            size = ND_width(n);
        if (ND_height(n) > size)
            size = ND_height(n);
    }
    return size;
}
 
static void place_node(Agraph_t * g, Agnode_t * n, nodelist_t * list)
{
    Agedge_t *e;
    bool placed = false;
    nodelist_t neighbors = {0};
 
    for (e = agfstout(g, n); e; e = agnxtout(g, e)) {
        LIST_APPEND(&neighbors, aghead(e));
        SET_NEIGHBOR(aghead(e));
    }
    for (e = agfstin(g, n); e; e = agnxtin(g, e)) {
        LIST_APPEND(&neighbors, agtail(e));
        SET_NEIGHBOR(agtail(e));
    }
 
    /* Look for 2 neighbors consecutive on list */
    if (LIST_SIZE(&neighbors) >= 2) {
        for (size_t one = 0; one < LIST_SIZE(list); ++one) {
            const size_t two = (one + 1) % LIST_SIZE(list);
 
            if (NEIGHBOR(LIST_GET(list, one)) && NEIGHBOR(LIST_GET(list, two))) {
                appendNodelist(list, one + 1, n);
                placed = true;
                break;
            }
        }
    }
 
    /* Find any neighbor on list */
    if (!placed && !LIST_IS_EMPTY(&neighbors)) {
        for (size_t one = 0; one < LIST_SIZE(list); ++one) {
            if (NEIGHBOR(LIST_GET(list, one))) {
                appendNodelist(list, one + 1, n);
                placed = true;
                break;
            }
        }
    }
 
    if (!placed)
        LIST_APPEND(list, n);
 
    for (size_t one = 0; one < LIST_SIZE(&neighbors); ++one)
        UNSET_NEIGHBOR(LIST_GET(&neighbors, one));
    LIST_FREE(&neighbors);
}
 
static void place_residual_nodes(Agraph_t * g, nodelist_t * list)
{
    Agnode_t *n;
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (!ONPATH(n))
            place_node(g, n, list);
    }
}
 
nodelist_t layout_block(Agraph_t *g, block_t *sn, double min_dist,
                        circ_state *state) {
    Agraph_t *copyG, *tree, *subg;
    int k;
    double theta, radius;
 
    subg = sn->sub_graph;
    block_graph(g, sn);         /* add induced edges */
 
    copyG = remove_pair_edges(subg, state);
 
    tree = spanning_tree(copyG, state);
    nodelist_t longest_path = find_longest_path(tree);
    place_residual_nodes(subg, &longest_path);
    /* at this point, longest_path is a list of all nodes in the block */
 
    /* apply crossing reduction algorithms here */
    longest_path = reduce_edge_crossings(longest_path, subg);
 
    size_t N = LIST_SIZE(&longest_path);
    const double largest_node = largest_nodesize(&longest_path);
    /* N*(min_dist+largest_node) is roughly circumference of required circle */
    if (N == 1)
        radius = 0;
    else
        radius = (double)N * (min_dist + largest_node) / (2 * M_PI);
 
    for (size_t item = 0; item < LIST_SIZE(&longest_path); ++item) {
        Agnode_t *n = LIST_GET(&longest_path, item);
        if (ISPARENT(n)) {
            /* QUESTION: Why is only one parent realigned? */
            realignNodelist(&longest_path, item);
            break;
        }
    }
 
    k = 0;
    for (size_t item = 0; item < LIST_SIZE(&longest_path); ++item) {
        Agnode_t *n = LIST_GET(&longest_path, item);
        POSITION(n) = k;
        PSI(n) = 0.0;
        theta = k * (2.0 * M_PI / (double)N);
 
        ND_pos(n)[0] = radius * cos(theta);
        ND_pos(n)[1] = radius * sin(theta);
 
        k++;
    }
 
    if (N == 1)
        sn->radius = largest_node / 2;
    else
        sn->radius = radius;
    sn->rad0 = sn->radius;
 
    /* initialize parent pos */
    sn->parent_pos = -1;
 
    agclose(copyG);
    return longest_path;
}
 
#ifdef DEBUG
void prTree(Agraph_t * g)
{
    Agnode_t *n;
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (TPARENT(n)) {
                        fprintf(stderr, "%s ", agnameof(n));
                        fprintf(stderr, "-> %s\n", agnameof(TPARENT(n)));
                }
    }
}
#endif