sccmap.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
 *************************************************************************/
 
 
/*
 * Written by Stephen North
 * Updated by Emden Gansner
 */
 
/*
 * This is a filter that reads a graph, searches for strongly
 * connected components, and writes each as a separate graph
 * along with a map of the components.
 */
 
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <cgraph/cgraph.h>
#include <cgraph/exit.h>
#include <cgraph/ingraphs.h>
#include <cgraph/stack.h>
#include <cgraph/unreachable.h>
 
#include <getopt.h>
#include "openFile.h"
 
#define INF UINT_MAX
 
typedef struct Agraphinfo_t {
    Agrec_t h;
    Agnode_t *rep;
} Agraphinfo_t;
 
typedef struct Agnodeinfo_t {
    Agrec_t h;
    unsigned int val;
    Agraph_t *scc;
} Agnodeinfo_t;
 
static Agnode_t *getrep(Agraph_t * g)
{
    return ((Agraphinfo_t *)g->base.data)->rep;
}
static void setrep(Agraph_t * g, Agnode_t * rep)
{
    ((Agraphinfo_t *)g->base.data)->rep = rep;
}
static Agraph_t *getscc(Agnode_t * n)
{
    return ((Agnodeinfo_t *)n->base.data)->scc;
}
static void setscc(Agnode_t * n, Agraph_t * scc)
{
    ((Agnodeinfo_t *)n->base.data)->scc = scc;
}
static unsigned getval(Agnode_t *n) {
    return ((Agnodeinfo_t *)n->base.data)->val;
}
static void setval(Agnode_t *n, unsigned v) {
    ((Agnodeinfo_t *)n->base.data)->val = v;
}
 
typedef struct {
    unsigned Comp;
    unsigned ID;
    int N_nodes_in_nontriv_SCC;
} sccstate;
 
static int wantDegenerateComp;
static int Silent;
static int StatsOnly;
static int Verbose;
static char *CmdName;
static char **Files;
static FILE *outfp;             /* output; stdout by default */
 
static void nodeInduce(Agraph_t * g, Agraph_t* map)
{
    Agnode_t *n;
    Agedge_t *e;
    Agraph_t* rootg = agroot (g);
 
    
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        for (e = agfstout(rootg, n); e; e = agnxtout(rootg, e)) {
            if (agsubnode(g, aghead(e), 0))
                agsubedge(g, e, 1);
            else {
                Agraph_t* tscc = getscc(agtail(e));
                Agraph_t* hscc = getscc(aghead(e));
                if (tscc && hscc)
                    agedge(map, getrep(tscc), getrep(hscc), NULL, 1);
            }
        }
    }
}
 
static unsigned visit(Agnode_t *n, Agraph_t *map, gv_stack_t *sp, sccstate *st) {
    unsigned int m, min;
    Agnode_t *t;
    Agraph_t *subg;
    Agedge_t *e;
 
    min = ++st->ID;
    setval(n, min);
    stack_push(sp, n);
 
    for (e = agfstout(n->root, n); e; e = agnxtout(n->root, e)) {
        t = aghead(e);
        if (getval(t) == 0)
            m = visit(t, map, sp, st);
        else
            m = getval(t);
        if (m < min)
            min = m;
    }
 
    if (getval(n) == min) {
        if (!wantDegenerateComp && stack_top(sp) == n) {
            setval(n, INF);
            stack_pop(sp);
        } else {
            char name[32];
            Agraph_t *G = agraphof(n);;
            snprintf(name, sizeof(name), "cluster_%u", st->Comp++);
            subg = agsubg(G, name, 1);
            agbindrec(subg, "scc_graph", sizeof(Agraphinfo_t), true);
            setrep(subg, agnode(map, name, 1));
            do {
                t = stack_pop(sp);
                agsubnode(subg, t, 1);
                setval(t, INF);
                setscc(t, subg);
                st->N_nodes_in_nontriv_SCC++;
            } while (t != n);
            nodeInduce(subg, map);
            if (!StatsOnly)
                agwrite(subg, outfp);
        }
    }
    return min;
}
 
static int label(Agnode_t * n, int nodecnt, int *edgecnt)
{
    Agedge_t *e;
 
    setval(n, 1);
    nodecnt++;
    for (e = agfstedge(n->root, n); e; e = agnxtedge(n->root, e, n)) {
        *edgecnt += 1;
        if (e->node == n)
            e = agopp(e);
        if (!getval(e->node))
            nodecnt = label(e->node, nodecnt, edgecnt);
    }
    return nodecnt;
}
 
static int
countComponents(Agraph_t * g, int *max_degree, float *nontree_frac)
{
    int nc = 0;
    int sum_edges = 0;
    int sum_nontree = 0;
    int deg;
    int n_edges;
    int n_nodes;
    Agnode_t *n;
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (!getval(n)) {
            nc++;
            n_edges = 0;
            n_nodes = label(n, 0, &n_edges);
            sum_edges += n_edges;
            sum_nontree += n_edges - n_nodes + 1;
        }
    }
    if (max_degree) {
        int maxd = 0;
        for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
            deg = agdegree(g, n, 1, 1);
            if (maxd < deg)
                maxd = deg;
            setval(n, 0);
        }
        *max_degree = maxd;
    }
    if (nontree_frac) {
        if (sum_edges > 0)
            *nontree_frac = (float) sum_nontree / (float) sum_edges;
        else
            *nontree_frac = 0.0;
    }
    return nc;
}
 
static void process(Agraph_t * G)
{
    Agnode_t *n;
    Agraph_t *map;
    int nc = 0;
    float nontree_frac = 0;
    int Maxdegree = 0;
    gv_stack_t stack = {0};
    sccstate state;
 
    aginit(G, AGRAPH, "scc_graph", sizeof(Agraphinfo_t), true);
    aginit(G, AGNODE, "scc_node", sizeof(Agnodeinfo_t), true);
    state.Comp = state.ID = 0;
    state.N_nodes_in_nontriv_SCC = 0;
 
    if (Verbose)
        nc = countComponents(G, &Maxdegree, &nontree_frac);
 
    map = agopen("scc_map", Agdirected, (Agdisc_t *) 0);
    for (n = agfstnode(G); n; n = agnxtnode(G, n))
        if (getval(n) == 0)
            visit(n, map, &stack, &state);
    stack_reset(&stack);
    if (!StatsOnly)
        agwrite(map, outfp);
    agclose(map);
 
    if (Verbose)
        fprintf(stderr, "%d %d %d %u %.4f %d %.4f\n",
                agnnodes(G), agnedges(G), nc, state.Comp,
                state.N_nodes_in_nontriv_SCC / (double) agnnodes(G),
                Maxdegree, nontree_frac);
    else if (!Silent)
        fprintf(stderr, "%d nodes, %d edges, %u strong components\n",
                agnnodes(G), agnedges(G), state.Comp);
 
}
 
static char *useString = "Usage: %s [-sdv?] <files>\n\
  -s           - only produce statistics\n\
  -S           - silent\n\
  -d           - allow degenerate components\n\
  -o<outfile>  - write to <outfile> (stdout)\n\
  -v           - verbose\n\
  -?           - print usage\n\
If no files are specified, stdin is used\n";
 
static void usage(int v)
{
    printf(useString, CmdName);
    graphviz_exit(v);
}
 
static void scanArgs(int argc, char **argv)
{
    int c;
 
    CmdName = argv[0];
    opterr = 0;
    while ((c = getopt(argc, argv, ":o:sdvS?")) != EOF) {
        switch (c) {
        case 's':
            StatsOnly = 1;
            break;
        case 'd':
            wantDegenerateComp = 1;
            break;
        case 'o':
            if (outfp != NULL)
                fclose(outfp);
            outfp = openFile(CmdName, optarg, "w");
            break;
        case 'v':
            Verbose = 1;
            Silent = 0;
            break;
        case 'S':
            Verbose = 0;
            Silent = 1;
            break;
        case ':':
            fprintf(stderr, "%s: option -%c missing argument - ignored\n", CmdName, optopt);
            break;
        case '?':
            if (optopt == '\0' || optopt == '?')
                usage(0);
            else {
                fprintf(stderr, "%s: option -%c unrecognized\n",
                        CmdName, optopt);
                usage(1);
            }
            break;
        default:
            UNREACHABLE();
        }
    }
    argv += optind;
    argc -= optind;
 
    if (argc > 0)
        Files = argv;
    if (!outfp)
        outfp = stdout;         /* stdout the default */
}
 
int main(int argc, char **argv)
{
    Agraph_t *g;
    ingraph_state ig;
 
    scanArgs(argc, argv);
    newIngraph(&ig, Files);
 
    while ((g = nextGraph(&ig)) != 0) {
        if (agisdirected(g))
            process(g);
        else
            fprintf(stderr, "Graph %s in %s is undirected - ignored\n",
                    agnameof(g), fileName(&ig));
        agclose(g);
    }
 
    graphviz_exit(0);
}