Expel Tarjan from his nest
- Nested functions are a gcc-extension and very non-portable. Refactor to eliminate the nesting by passing the "global" variables via a struct from detectSCCs().
This commit is contained in:
Panu Matilainen
parent
8abe568e00
commit
b9168b6735
171
lib/order.c
171
lib/order.c
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@ -305,100 +305,107 @@ static void addQ(tsortInfo p, tsortInfo * qp, tsortInfo * rp,
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}
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}
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typedef struct sccData_s {
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int index; /* DFS node number counter */
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tsortInfo *stack; /* Stack of nodes */
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int stackcnt; /* Stack top counter */
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scc SCCs; /* Array of SCC's found */
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int sccCnt; /* Number of SCC's found */
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} * sccData;
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static void tarjan(sccData sd, tsortInfo tsi) {
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tsortInfo tsi_q;
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relation rel;
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/* use negative index numbers */
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sd->index--;
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/* Set the depth index for p */
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tsi->tsi_SccIdx = sd->index;
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tsi->tsi_SccLowlink = sd->index;
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sd->stack[sd->stackcnt++] = tsi; /* Push p on the stack */
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for (rel=tsi->tsi_relations; rel != NULL; rel=rel->rel_next) {
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/* Consider successors of p */
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tsi_q = rel->rel_suc;
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if (tsi_q->tsi_SccIdx > 0)
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/* Ignore already found SCCs */
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continue;
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if (tsi_q->tsi_SccIdx == 0){
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/* Was successor q not yet visited? */
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tarjan(sd, tsi_q); /* Recurse */
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/* negative index numers: use max as it is closer to 0 */
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tsi->tsi_SccLowlink = (
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tsi->tsi_SccLowlink > tsi_q->tsi_SccLowlink
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? tsi->tsi_SccLowlink : tsi_q->tsi_SccLowlink);
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} else {
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tsi->tsi_SccLowlink = (
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tsi->tsi_SccLowlink > tsi_q->tsi_SccIdx
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? tsi->tsi_SccLowlink : tsi_q->tsi_SccIdx);
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}
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}
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if (tsi->tsi_SccLowlink == tsi->tsi_SccIdx) {
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/* v is the root of an SCC? */
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if (sd->stack[sd->stackcnt-1] == tsi) {
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/* ignore trivial SCCs */
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tsi_q = sd->stack[--sd->stackcnt];
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tsi_q->tsi_SccIdx = 1;
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} else {
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int stackIdx = sd->stackcnt;
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do {
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tsi_q = sd->stack[--stackIdx];
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tsi_q->tsi_SccIdx = sd->sccCnt;
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} while (tsi_q != tsi);
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stackIdx = sd->stackcnt;
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do {
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tsi_q = sd->stack[--stackIdx];
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/* Calculate count for the SCC */
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sd->SCCs[sd->sccCnt].count += tsi_q->tsi_count;
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/* Subtract internal relations */
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for (rel=tsi_q->tsi_relations; rel != NULL;
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rel=rel->rel_next) {
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if (rel->rel_suc != tsi_q &&
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rel->rel_suc->tsi_SccIdx == sd->sccCnt)
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sd->SCCs[sd->sccCnt].count--;
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}
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} while (tsi_q != tsi);
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sd->SCCs[sd->sccCnt].size = sd->stackcnt - stackIdx;
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/* copy members */
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sd->SCCs[sd->sccCnt].members = xcalloc(sd->SCCs[sd->sccCnt].size,
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sizeof(tsortInfo));
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memcpy(sd->SCCs[sd->sccCnt].members, sd->stack + stackIdx,
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sd->SCCs[sd->sccCnt].size * sizeof(tsortInfo));
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sd->stackcnt = stackIdx;
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sd->sccCnt++;
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}
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}
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}
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/* Search for SCCs and return an array last entry has a .size of 0 */
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static scc detectSCCs(tsortInfo orderInfo, int nelem, int debugloops)
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{
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int index = 0; /* DFS node number counter */
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tsortInfo stack[nelem]; /* An empty stack of nodes */
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int stackcnt = 0;
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int sccCnt = 2;
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scc SCCs = xcalloc(nelem+3, sizeof(struct scc_s));
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auto void tarjan(tsortInfo tsi);
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void tarjan(tsortInfo tsi) {
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tsortInfo tsi_q;
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relation rel;
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/* use negative index numbers */
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index--;
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/* Set the depth index for p */
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tsi->tsi_SccIdx = index;
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tsi->tsi_SccLowlink = index;
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stack[stackcnt++] = tsi; /* Push p on the stack */
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for (rel=tsi->tsi_relations; rel != NULL; rel=rel->rel_next) {
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/* Consider successors of p */
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tsi_q = rel->rel_suc;
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if (tsi_q->tsi_SccIdx > 0)
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/* Ignore already found SCCs */
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continue;
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if (tsi_q->tsi_SccIdx == 0){
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/* Was successor q not yet visited? */
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tarjan(tsi_q); /* Recurse */
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/* negative index numers: use max as it is closer to 0 */
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tsi->tsi_SccLowlink = (
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tsi->tsi_SccLowlink > tsi_q->tsi_SccLowlink
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? tsi->tsi_SccLowlink : tsi_q->tsi_SccLowlink);
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} else {
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tsi->tsi_SccLowlink = (
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tsi->tsi_SccLowlink > tsi_q->tsi_SccIdx
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? tsi->tsi_SccLowlink : tsi_q->tsi_SccIdx);
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}
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}
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if (tsi->tsi_SccLowlink == tsi->tsi_SccIdx) {
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/* v is the root of an SCC? */
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if (stack[stackcnt-1] == tsi) {
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/* ignore trivial SCCs */
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tsi_q = stack[--stackcnt];
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tsi_q->tsi_SccIdx = 1;
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} else {
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int stackIdx = stackcnt;
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do {
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tsi_q = stack[--stackIdx];
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tsi_q->tsi_SccIdx = sccCnt;
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} while (tsi_q != tsi);
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stackIdx = stackcnt;
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do {
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tsi_q = stack[--stackIdx];
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/* Calculate count for the SCC */
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SCCs[sccCnt].count += tsi_q->tsi_count;
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/* Subtract internal relations */
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for (rel=tsi_q->tsi_relations; rel != NULL;
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rel=rel->rel_next) {
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if (rel->rel_suc != tsi_q &&
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rel->rel_suc->tsi_SccIdx == sccCnt)
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SCCs[sccCnt].count--;
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}
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} while (tsi_q != tsi);
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SCCs[sccCnt].size = stackcnt - stackIdx;
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/* copy members */
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SCCs[sccCnt].members = xcalloc(SCCs[sccCnt].size,
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sizeof(tsortInfo));
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memcpy(SCCs[sccCnt].members, stack + stackIdx,
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SCCs[sccCnt].size * sizeof(tsortInfo));
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stackcnt = stackIdx;
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sccCnt++;
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}
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}
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}
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/* Set up data structures needed for the tarjan algorithm */
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scc SCCs = xcalloc(nelem+3, sizeof(*SCCs));
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tsortInfo *stack = xcalloc(nelem, sizeof(*stack));
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struct sccData_s sd = { 0, stack, 0, SCCs, 2 };
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for (int i = 0; i < nelem; i++) {
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tsortInfo tsi = &orderInfo[i];
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/* Start a DFS at each node */
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if (tsi->tsi_SccIdx == 0)
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tarjan(tsi);
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tarjan(&sd, tsi);
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}
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SCCs = xrealloc(SCCs, (sccCnt+1)*sizeof(struct scc_s));
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free(stack);
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SCCs = xrealloc(SCCs, (sd.sccCnt+1)*sizeof(struct scc_s));
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/* Debug output */
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if (sccCnt > 2) {
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if (sd.sccCnt > 2) {
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int msglvl = debugloops ? RPMLOG_WARNING : RPMLOG_DEBUG;
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rpmlog(msglvl, "%i Strongly Connected Components\n", sccCnt-2);
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for (int i = 2; i < sccCnt; i++) {
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rpmlog(msglvl, "%i Strongly Connected Components\n", sd.sccCnt-2);
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for (int i = 2; i < sd.sccCnt; i++) {
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rpmlog(msglvl, "SCC #%i: requires %i packages\n",
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i, SCCs[i].count);
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/* loop over members */
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