888 lines
22 KiB
C
888 lines
22 KiB
C
#include <u.h>
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#include <libc.h>
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#include <sat.h>
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#include "impl.h"
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/* the solver follows Algorithm C from Knuth's The Art of Computer Programming, Vol. 4, Fascicle 6 */
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#define verbosestate 0
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#define verboseforcing 0
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#define verboseconflict 0
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#define paranoia 0
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#define sanity(s) if(paranoia) satsanity(s)
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void
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sataddtrail(SATSolve *s, int l)
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{
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s->trail[s->ntrail++] = l;
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s->lit[l].val = 1;
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s->lit[NOT(l)].val = 0;
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s->var[VAR(l)].lvl = s->lvl;
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s->agility -= s->agility >> 13;
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if(((s->var[VAR(l)].flags ^ l) & 1) != 0)
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s->agility += 1<<19;
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if(verbosestate) satprintstate(s);
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}
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/* compute watchlists from scratch */
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static void
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rewatch(SATSolve *s)
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{
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SATLit *l;
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SATClause *c;
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int i, j, x;
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for(l = s->lit; l < s->lit + 2*s->nvar; l++)
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l->watch = nil;
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for(c = s->cl; c != nil; c = c->next)
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for(i = 0; i < 2; i++){
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if(s->lit[c->l[i]].val == 0)
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for(j = 2; j < c->n; j++)
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if(s->lit[c->l[j]].val != 0){
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x = c->l[i], c->l[i] = c->l[j], c->l[j] = x;
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break;
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}
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c->watch[i] = s->lit[c->l[i]].watch;
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s->lit[c->l[i]].watch = c;
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}
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}
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/* jump back to decision level d */
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void
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satbackjump(SATSolve *s, int d)
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{
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int l;
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SATVar *v;
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if(s->lvl == d) return;
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while(s->ntrail > s->decbd[d + 1]){
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l = s->trail[--s->ntrail];
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v = &s->var[VAR(l)];
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if((v->flags & VARUSER) != 0){ /* don't delete user assignments */
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s->ntrail++;
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break;
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}
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s->lit[l].val = -1;
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s->lit[NOT(l)].val = -1;
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v->flags = v->flags & ~1 | l & 1;
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v->lvl = -1;
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v->reason = nil;
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v->isbinreason = 0;
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if(v->heaploc < 0)
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satheapput(s, v);
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}
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s->lvl = d;
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if(s->forptr > s->ntrail) s->forptr = s->ntrail;
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if(s->binptr > s->ntrail) s->binptr = s->ntrail;
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if(verbosestate) satprintstate(s);
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}
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static void
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solvinit(SATSolve *s)
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{
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satdebuginit(s);
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satheapreset(s);
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s->decbd = satrealloc(s, s->decbd, (s->nvar + 1) * sizeof(int));
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s->decbd[0] = 0;
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s->trail = satrealloc(s, s->trail, sizeof(int) * s->nvar);
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s->fullrlits = satrealloc(s, s->fullrlits, sizeof(int) * s->nvar);
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s->lvlstamp = satrealloc(s, s->lvlstamp, sizeof(int) * s->nvar);
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memset(s->lvlstamp, 0, sizeof(int) * s->nvar);
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if(s->cflclalloc == 0){
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s->cflcl = satrealloc(s, s->cflcl, CFLCLALLOC * sizeof(int));
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s->cflclalloc = CFLCLALLOC;
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}
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rewatch(s);
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s->conflicts = 0;
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s->nextpurge = s->purgeΔ;
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s->purgeival = s->purgeΔ;
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s->nextflush = 1;
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s->flushu = 1;
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s->flushv = 1;
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s->flushθ = s->flushψ;
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s->agility = 0;
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satbackjump(s, 0);
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s->forptr = 0;
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s->binptr = 0;
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}
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void
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satcleanup(SATSolve *s, int all)
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{
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SATBlock *b, *bn;
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if(all){
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*s->lastp[0] = nil;
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s->learncl = nil;
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s->lastp[1] = &s->learncl;
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s->ncl = s->ncl0;
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}
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for(b = s->bl[1].next; b != &s->bl[1]; b = bn){
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bn = b->next;
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if(b->last != nil && !all) continue;
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b->next->prev = b->prev;
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b->prev->next = b->next;
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free(b);
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}
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s->lastbl = s->bl[1].prev;
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free(s->fullrlits);
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s->fullrlits = nil;
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free(s->lvlstamp);
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s->lvlstamp = nil;
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free(s->cflcl);
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s->cflcl = nil;
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s->cflclalloc = 0;
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}
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static void
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stampoverflow(SATSolve *s)
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{
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int i;
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for(i = 0; i < s->nvar; i++){
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s->var[i].stamp = 0;
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s->lvlstamp[i] = 0;
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}
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s->stamp = -2;
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}
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/* "bump" the variable, i.e. increase its activity score. reduce all score when one exceeds MAXACTIVITY (1e100) */
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static void
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varbump(SATSolve *s, SATVar *v)
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{
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v->activity += s->Δactivity;
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satreheap(s, v);
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if(v->activity < MAXACTIVITY) return;
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for(v = s->var; v < s->var + s->nvar; v++)
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if(v->activity != 0){
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v->activity /= MAXACTIVITY;
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if(v->activity < ε)
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v->activity = ε;
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}
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s->Δactivity /= MAXACTIVITY;
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}
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/* ditto for clauses */
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static void
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clausebump(SATSolve *s, SATClause *c)
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{
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c->activity += s->Δclactivity;
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if(c->activity < MAXACTIVITY) return;
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for(c = s->cl; c != nil; c = c->next)
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if(c->activity != 0){
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c->activity /= MAXACTIVITY;
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if(c->activity < ε)
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c->activity = ε;
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}
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s->Δclactivity /= MAXACTIVITY;
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}
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/* pick a literal. normally we pick the variable with highest activity from the heap. sometimes we goof and pick a random one. */
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static void
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decision(SATSolve *s)
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{
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SATVar *v;
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s->decbd[++s->lvl] = s->ntrail;
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if((uint)s->randfn(s->randaux) < s->goofprob){
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v = s->heap[satnrand(s, s->nheap)];
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if(v->lvl < 0)
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goto gotv;
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}
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do
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v = satheaptake(s);
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while(v->lvl >= 0);
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gotv:
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sataddtrail(s, 2 * (v - s->var) + (v->flags & VARPHASE));
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}
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/* go through the watchlist of a literal that just turned out false. */
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/* full == 1 records the first conflict and goes on rather than aborting immediately */
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static SATClause *
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forcing(SATSolve *s, int l, int full)
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{
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SATClause **cp, *rc, *c, *xp;
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int v0;
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int x, j;
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cp = &s->lit[l].watch;
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rc = nil;
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if(verboseforcing) print("forcing literal %d\n", signf(l));
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while(c = *cp, c != nil){
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if(l == c->l[0]){
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/* this swap implies that the reason r for a literal l always has r->l[0]==l */
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x = c->l[1], c->l[1] = c->l[0], c->l[0] = x;
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xp = c->watch[1], c->watch[1] = c->watch[0], c->watch[0] = xp;
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}
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assert(c->l[1] == l);
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v0 = s->lit[c->l[0]].val;
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if(v0 > 0) /* the clause is true anyway */
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goto next;
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for(j = 2; j < c->n; j++)
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if(s->lit[c->l[j]].val != 0){
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/* found another literal to watch for this clause */
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if(verboseforcing) print("moving clause %+Γ onto watchlist %d\n", c, signf(c->l[j]));
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*cp = c->watch[1];
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x = c->l[j], c->l[j] = c->l[1], c->l[1] = x;
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c->watch[1] = s->lit[x].watch;
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s->lit[x].watch = c;
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goto cont;
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}
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if(v0 == 0){
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/* conflict */
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if(!full) return c;
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if(rc == nil) rc = c;
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goto next;
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}
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if(verboseforcing) print("inferring %d using clause %+Γ\n", signf(c->l[0]), c);
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sataddtrail(s, c->l[0]);
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s->var[VAR(c->l[0])].reason = c;
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next:
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cp = &c->watch[1];
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cont: ;
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}
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return rc;
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}
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/* forcing() for binary implications */
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static uvlong
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binforcing(SATSolve *s, int l, int full)
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{
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SATLit *lp;
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int i, m;
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uvlong rc;
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lp = &s->lit[l];
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rc = 0;
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if(verboseforcing && lp->nbimp > 0) print("forcing literal %d (binary)\n", signf(l));
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for(i = 0; i < lp->nbimp; i++){
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m = lp->bimp[i];
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switch(s->lit[m].val){
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case -1:
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if(verboseforcing) print("inferring %d using binary clause (%d) ∨ %d\n", signf(m), -signf(l), signf(m));
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sataddtrail(s, m);
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s->var[VAR(m)].binreason = NOT(l);
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s->var[VAR(m)].isbinreason = 1;
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break;
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case 0:
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if(verboseforcing) print("conflict (%d) ∨ (%d)\n", -signf(l), signf(m));
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if(rc == 0) rc = (uvlong)NOT(l) << 32 | (uint)m;
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if(!full) return rc;
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break;
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}
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}
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return rc;
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}
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/* check if we can discard the previously learned clause because the current one subsumes it */
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static int
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checkdiscard(SATSolve *s)
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{
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SATClause *c;
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SATVar *v;
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int q, j;
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if(s->lastp[1] == &s->learncl) return 0;
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c = (SATClause*) ((uchar*) s->lastp[1] - (uchar*) &((SATClause*)0)->next);
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if(s->lit[c->l[0]].val >= 0) return 0; /* clause is a reason, hands off */
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q = s->ncflcl;
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for(j = c->n - 1; q > 0 && j >= q; j--){
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v = &s->var[VAR(c->l[j])];
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/* check if literal is in the current clause */
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if(c->l[j] == s->cflcl[0] || (uint)v->lvl <= s->cfllvl && v->stamp == s->stamp)
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q--;
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}
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return q == 0;
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}
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/* add the clause we just learned to our collection */
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static SATClause *
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learn(SATSolve *s, int notriv)
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{
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SATClause *r;
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int i, l, triv;
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/* clauses that are too complicated are not worth it. learn the trivial clause (all decisions negated) instead */
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if(triv = !notriv && s->ncflcl > s->lvl + s->trivlim){
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assert(s->lvl + 1 <= s->cflclalloc);
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for(i = 1; i <= s->lvl; i++)
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s->cflcl[i] = NOT(s->trail[s->decbd[s->lvl + 1 - i]]);
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s->ncflcl = s->lvl + 1;
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}
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if(s->ncflcl == 1) /* unit clauses are handled by putting them on the trail in conflict() */
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return nil;
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if(!triv && checkdiscard(s))
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r = satreplclause(s, s->ncflcl);
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else
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r = satnewclause(s, s->ncflcl, 1);
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r->n = s->ncflcl;
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memcpy(r->l, s->cflcl, s->ncflcl * sizeof(int));
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for(i = 0; i < 2; i++){
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l = r->l[i];
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r->watch[i] = s->lit[l].watch;
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s->lit[l].watch = r;
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}
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return r;
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}
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/* recursive procedure to determine if a literal is redundant.
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* to avoid repeated work, each known redundant literal is stamped with stamp+1
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* and each known nonredundant literal is stamped with stamp+2.
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*/
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static int
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redundant(SATSolve *s, int l)
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{
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SATVar *v, *w;
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SATClause *c;
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int i, r;
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v = &s->var[VAR(l)];
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if(v->isbinreason){
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/* stupid special case code */
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r = v->binreason;
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w = &s->var[VAR(r)];
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if(w->lvl != 0){
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if(w->stamp == s->stamp + 2)
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return 0;
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if(w->stamp < s->stamp && (s->lvlstamp[w->lvl] < s->stamp || !redundant(s, r))){
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w->stamp = s->stamp + 2;
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return 0;
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}
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}
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v->stamp = s->stamp + 1;
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return 1;
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}
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if(v->reason == nil) return 0; /* decision literals are never redundant */
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c = v->reason;
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for(i = 0; i < c->n; i++){
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if(c->l[i] == NOT(l)) continue;
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w = &s->var[VAR(c->l[i])];
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if(w->lvl == 0)
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continue; /* literals at level 0 are redundant */
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if(w->stamp == s->stamp + 2)
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return 0;
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/* if the literal is not in the clause or known redundant, check if it is redundant */
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/* we can skip the check if the level is not stamped: */
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/* if there are no literals at the same level in the clause, it must be nonredundant */
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if(w->stamp < s->stamp && (s->lvlstamp[w->lvl] < s->stamp || !redundant(s, c->l[i]))){
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w->stamp = s->stamp + 2;
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return 0;
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}
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}
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v->stamp = s->stamp + 1;
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return 1;
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}
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/* "blitting" a literal means to either add it to the conflict clause
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* (if v->lvl < s->lvl) or to increment the counter of literals to be
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* resolved, plus some bookkeeping. */
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static void
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blit(SATSolve *s, int l)
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{
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SATVar *v;
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int p;
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v = &s->var[VAR(l)];
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if(v->stamp == s->stamp) return;
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v->stamp = s->stamp;
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p = v->lvl;
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if(p == 0) return;
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if(verboseconflict) print("stamp %d %s (ctr=%d)\n", signf(l), p == s->lvl ? "and increment" : "and collect", s->cflctr);
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varbump(s, v);
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if(p == s->lvl){
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s->cflctr++;
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return;
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}
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if(s->ncflcl >= s->cflclalloc){
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s->cflcl = satrealloc(s, s->cflcl, (s->cflclalloc + CFLCLALLOC) * sizeof(int));
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s->cflclalloc += CFLCLALLOC;
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}
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s->cflcl[s->ncflcl++] = l;
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if(p > s->cfllvl) s->cfllvl = p;
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/* lvlstamp[p] == stamp if there is exactly one literal and ==stamp+1 if there is more than one literal on level p */
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if(s->lvlstamp[p] <= s->stamp)
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s->lvlstamp[p] = s->stamp + (s->lvlstamp[p] == s->stamp);
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}
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/* to resolve a conflict, we start with the conflict clause and use
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* resolution (a ∨ b and ¬a ∨ c imply b ∨ c) with the reasons for the
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* literals to remove all but one literal at the current level. this
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* gives a new "learned" clause with all literals false and we jump back
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* to the second-highest level in it. at this point, the clause implies
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* the one remaining literal and we can continue.
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* to do this quickly, rather than explicitly apply resolution, we keep a
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* counter of literals at the highest level (unresolved literals) and an
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* array with all other literals (which will become the learned clause). */
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static void
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conflict(SATSolve *s, SATClause *c, uvlong bin, int full)
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{
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int i, j, l, p, *nl, found;
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SATVar *v;
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SATClause *r;
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if(verboseconflict) satprintstate(s);
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/* choose a new unique stamp value */
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if(s->stamp >= (uint)-3)
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stampoverflow(s);
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s->stamp += 3;
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s->ncflcl = 1;
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s->cflctr = 0;
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s->cfllvl = 0;
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/* we start by blitting each literal in the conflict clause */
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if(c != nil){
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clausebump(s, c);
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for(i = 0; i < c->n; i++)
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blit(s, c->l[i]);
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/* if there is only one literal l at the current level, we should have inferred ¬l at a lower level (bug). */
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if(s->cflctr <= 1){
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satprintstate(s);
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print("conflict clause %+Γ\n", c);
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assert(s->cflctr > 1);
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}
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}else{
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blit(s, bin);
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blit(s, bin>>32);
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if(s->cflctr <= 1){
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satprintstate(s);
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print("binary conflict clause %d ∨ %d\n", (int)(bin>>32), (int)bin);
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assert(s->cflctr > 1);
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}
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}
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/* now we go backwards through the trail, decrementing the unresolved literal counter at each stamped literal */
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/* and blitting the literals in their reason */
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for(i = s->ntrail; --i >= 0; ){
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v = &s->var[VAR(s->trail[i])];
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if(v->stamp != s->stamp) continue;
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if(verboseconflict) print("trail literal %d\n", signf(s->trail[i]));
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if(--s->cflctr == 0) break;
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if(v->isbinreason)
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blit(s, v->binreason);
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else if((r = v->reason) != nil){
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clausebump(s, r);
|
||
for(j = 0; j < r->n; j++)
|
||
blit(s, r->l[j]);
|
||
}
|
||
}
|
||
/* i should point to the one remaining literal at the current level */
|
||
assert(i >= 0);
|
||
nl = s->cflcl;
|
||
nl[0] = NOT(s->trail[i]);
|
||
found = 0;
|
||
/* delete redundant literals. note we must watch a literal at cfllvl, so put it in l[1]. */
|
||
for(i = 1, j = 1; i < s->ncflcl; i++){
|
||
l = nl[i];
|
||
p = s->var[VAR(nl[i])].lvl;
|
||
/* lvlstamp[p] != s->stamp + 1 => only one literal at level p => must be nonredundant */
|
||
if(s->lvlstamp[p] != s->stamp + 1 || !redundant(s, l))
|
||
if(found || p < s->cfllvl)
|
||
nl[j++] = nl[i];
|
||
else{
|
||
/* watch this literal */
|
||
l = nl[i], nl[j++] = nl[1], nl[1] = l;
|
||
found = 1;
|
||
}
|
||
}
|
||
s->ncflcl = j;
|
||
if(!full){
|
||
/* normal mode: jump back and add to trail right away */
|
||
satbackjump(s, s->cfllvl);
|
||
sataddtrail(s, nl[0]);
|
||
}else{
|
||
/* purging: record minimum cfllvl and literals at that level */
|
||
if(s->cfllvl < s->fullrlvl){
|
||
s->fullrlvl = s->cfllvl;
|
||
s->nfullrlits = 0;
|
||
}
|
||
s->fullrlits[s->nfullrlits++] = nl[0];
|
||
}
|
||
r = learn(s, full);
|
||
if(!full && r != nil)
|
||
s->var[VAR(nl[0])].reason = r;
|
||
if(verboseconflict)
|
||
if(r != nil)
|
||
print("learned %+Γ\n", r);
|
||
else
|
||
print("learned %d\n", signf(nl[0]));
|
||
s->Δactivity *= s->varρ;
|
||
s->Δclactivity *= s->clauseρ;
|
||
s->conflicts++;
|
||
}
|
||
|
||
/* to purge, we need a fullrun that assigns values to all variables.
|
||
* during this we record the first conflict at each level, to be resolved
|
||
* later. otherwise this is just a copy of the main loop which never
|
||
* purges or flushes. */
|
||
static int
|
||
fullrun(SATSolve *s)
|
||
{
|
||
int l;
|
||
uvlong b;
|
||
SATClause *c;
|
||
|
||
while(s->ntrail < s->nvar){
|
||
decision(s);
|
||
re:
|
||
while(s->binptr < s->ntrail){
|
||
l = s->trail[s->binptr++];
|
||
b = binforcing(s, l, 1);
|
||
if(b != 0){
|
||
if(s->lvl == 0){
|
||
s->unsat = 1;
|
||
return -1;
|
||
}
|
||
if(s->nfullrcfl == 0 || s->lvl > CFLLVL(s->fullrcfl[s->nfullrcfl-1])){
|
||
s->fullrcfl = satrealloc(s, s->fullrcfl, sizeof(SATConflict) * (s->nfullrcfl + 1));
|
||
s->fullrcfl[s->nfullrcfl].lvl = 1<<31 | s->lvl;
|
||
s->fullrcfl[s->nfullrcfl++].b = b;
|
||
}
|
||
}
|
||
sanity(s);
|
||
}
|
||
while(s->forptr < s->ntrail){
|
||
l = s->trail[s->forptr++];
|
||
c = forcing(s, NOT(l), 1);
|
||
if(c != nil){
|
||
if(s->lvl == 0){
|
||
s->unsat = 1;
|
||
return -1;
|
||
}
|
||
if(s->nfullrcfl == 0 || s->lvl > CFLLVL(s->fullrcfl[s->nfullrcfl-1])){
|
||
s->fullrcfl = satrealloc(s, s->fullrcfl, sizeof(SATConflict) * (s->nfullrcfl + 1));
|
||
s->fullrcfl[s->nfullrcfl].lvl = s->lvl;
|
||
s->fullrcfl[s->nfullrcfl++].c = c;
|
||
}
|
||
}
|
||
}
|
||
if(s->binptr < s->ntrail) goto re;
|
||
}
|
||
return 0;
|
||
}
|
||
|
||
/* assign range scores to all clauses.
|
||
* p == number of levels that have positive literals in the clause.
|
||
* r == number of levels that have literals in the clause.
|
||
* range == min(floor(16 * (p + α (r - p))), 255) with magic constant α. */
|
||
static void
|
||
ranges(SATSolve *s)
|
||
{
|
||
SATClause *c;
|
||
int p, r, k, l, v;
|
||
uint ci;
|
||
|
||
ci = 2;
|
||
memset(s->lvlstamp, 0, sizeof(int) * s->nvar);
|
||
memset(s->rangecnt, 0, sizeof(s->rangecnt));
|
||
for(c = s->learncl; c != nil; c = c->next, ci += 2){
|
||
if(!s->var[VAR(c->l[0])].binreason && s->var[VAR(c->l[0])].reason == c){
|
||
c->range = 0;
|
||
s->rangecnt[0]++;
|
||
continue;
|
||
}
|
||
p = 0;
|
||
r = 0;
|
||
for(k = 0; k < c->n; k++){
|
||
l = c->l[k];
|
||
v = s->var[VAR(l)].lvl;
|
||
if(v == 0){
|
||
if(s->lit[l].val == 1){
|
||
c->range = 256;
|
||
goto next;
|
||
}
|
||
}else{
|
||
if(s->lvlstamp[v] < ci){
|
||
s->lvlstamp[v] = ci;
|
||
r++;
|
||
}
|
||
if(s->lvlstamp[v] == ci && s->lit[l].val == 1){
|
||
s->lvlstamp[v] = ci + 1;
|
||
p++;
|
||
}
|
||
}
|
||
}
|
||
r = 16 * (p + s->purgeα * (r - p));
|
||
if(r > 255) r = 255;
|
||
c->range = r;
|
||
s->rangecnt[r]++;
|
||
next: ;
|
||
}
|
||
}
|
||
|
||
/* resolve conflicts found during fullrun() */
|
||
static void
|
||
fullrconflicts(SATSolve *s)
|
||
{
|
||
SATConflict *cfl;
|
||
int i;
|
||
|
||
s->fullrlvl = s->lvl;
|
||
s->nfullrlits = 0;
|
||
for(cfl = &s->fullrcfl[s->nfullrcfl - 1]; cfl >= s->fullrcfl; cfl--){
|
||
satbackjump(s, CFLLVL(*cfl));
|
||
if(cfl->lvl < 0)
|
||
conflict(s, nil, cfl->b, 1);
|
||
else
|
||
conflict(s, cfl->c, 0, 1);
|
||
}
|
||
satbackjump(s, 0);
|
||
if(s->fullrlvl == 0)
|
||
for(i = 0; i < s->nfullrlits; i++)
|
||
sataddtrail(s, s->fullrlits[i]);
|
||
free(s->fullrcfl);
|
||
s->fullrcfl = nil;
|
||
}
|
||
|
||
/* note that nil > *, this simplifies the algorithm by having nil "bubble" to the top */
|
||
static int
|
||
actgt(SATClause *a, SATClause *b)
|
||
{
|
||
if(b == nil) return 0;
|
||
if(a == nil) return 1;
|
||
return a->activity > b->activity || a->activity == b->activity && a > b;
|
||
}
|
||
|
||
/* select n clauses to keep
|
||
* first we find the upper limit j on the range score
|
||
* to get the exact number, we move htot clauses from j to j+1
|
||
* to this end, we put them in a max-heap of size htot, sorted by activity,
|
||
* continually replacing the largest element if we find a less active clause.
|
||
* the heap starts out filled with nil and the nil are replaced during the first
|
||
* htot iterations. */
|
||
#define LEFT(i) (2*(i)+1)
|
||
#define RIGHT(i) (2*(i)+2)
|
||
static int
|
||
judgement(SATSolve *s, int n)
|
||
{
|
||
int cnt, i, j, htot, m;
|
||
SATClause *c, **h, *z;
|
||
|
||
cnt = 0;
|
||
for(j = 0; j < 256; j++){
|
||
cnt += s->rangecnt[j];
|
||
if(cnt >= n) break;
|
||
}
|
||
if(j == 256) return j;
|
||
if(cnt > n){
|
||
htot = cnt - n;
|
||
h = satrealloc(s, nil, sizeof(SATClause *) * htot);
|
||
memset(h, 0, sizeof(SATClause *) * htot);
|
||
for(c = s->learncl; c != nil; c = c->next){
|
||
if(c->range != j || actgt(c, h[0])) continue;
|
||
h[0] = c;
|
||
m = 0;
|
||
for(;;){
|
||
i = m;
|
||
if(LEFT(i) < htot && actgt(h[LEFT(i)], h[m])) m = LEFT(i);
|
||
if(RIGHT(i) < htot && actgt(h[RIGHT(i)], h[m])) m = RIGHT(i);
|
||
if(i == m) break;
|
||
z = h[i], h[i] = h[m], h[m] = z;
|
||
}
|
||
}
|
||
for(i = 0; i < htot; i++)
|
||
if(h[i] != nil)
|
||
h[i]->range = j + 1;
|
||
free(h);
|
||
}
|
||
return j;
|
||
}
|
||
|
||
/* during purging we remove permanently false literals from learned clauses.
|
||
* returns 1 if the clause can be deleted entirely. */
|
||
static int
|
||
cleanupclause(SATSolve *s, SATClause *c)
|
||
{
|
||
int i, k;
|
||
|
||
for(i = 0; i < c->n; i++)
|
||
if(s->lit[c->l[i]].val == 0)
|
||
break;
|
||
if(i == c->n) return 0;
|
||
for(k = i; i < c->n; i++)
|
||
if(s->lit[c->l[i]].val != 0)
|
||
c->l[k++] = c->l[i];
|
||
c->n = k;
|
||
if(k > 1) return 0;
|
||
if(k == 0)
|
||
s->unsat = 1;
|
||
else if(s->lit[c->l[0]].val < 0)
|
||
sataddtrail(s, c->l[0]);
|
||
return 1;
|
||
}
|
||
|
||
/* delete clauses by overwriting them. don't delete empty blocks; we're going to fill them up soon enough again. */
|
||
static void
|
||
execution(SATSolve *s, int j)
|
||
{
|
||
SATClause *c, *n, **cp, *p;
|
||
SATBlock *b;
|
||
SATVar *v0;
|
||
int f, sz;
|
||
|
||
b = s->bl[1].next;
|
||
p = (SATClause*) b->data;
|
||
s->ncl = s->ncl0;
|
||
cp = &s->learncl;
|
||
for(c = p; c != nil; c = n){
|
||
n = c->next;
|
||
if(c->range > j || cleanupclause(s, c))
|
||
continue;
|
||
sz = sizeof(SATClause) + (c->n - 1) * sizeof(int);
|
||
f = (uchar*)b + SATBLOCKSZ - (uchar*)p;
|
||
if(f < sz){
|
||
memset(p, 0, f);
|
||
b = b->next;
|
||
assert(b != &s->bl[1]);
|
||
p = (SATClause *) b->data;
|
||
}
|
||
b->last = p;
|
||
/* update reason field of the first variable (if applicable) */
|
||
v0 = &s->var[VAR(c->l[0])];
|
||
if(!v0->isbinreason && v0->reason == c)
|
||
v0->reason = p;
|
||
memmove(p, c, sz);
|
||
*cp = p;
|
||
cp = &p->next;
|
||
p = (void*)((uintptr)p + sz + CLAUSEALIGN - 1 & -CLAUSEALIGN);
|
||
b->end = p;
|
||
s->ncl++;
|
||
}
|
||
*cp = nil;
|
||
*s->lastp[0] = s->learncl;
|
||
s->lastp[1] = cp;
|
||
s->lastbl = b;
|
||
f = (uchar*)b + SATBLOCKSZ - (uchar*)p;
|
||
memset(p, 0, f);
|
||
for(b = b->next; b != &s->bl[1]; b = b->next){
|
||
b->last = nil;
|
||
b->end = b->data;
|
||
}
|
||
}
|
||
|
||
static void
|
||
thepurge(SATSolve *s)
|
||
{
|
||
int nkeep, i, j;
|
||
SATVar *v;
|
||
|
||
s->purgeival += s->purgeδ;
|
||
s->nextpurge = s->conflicts + s->purgeival;
|
||
nkeep = (s->ncl - s->ncl0) / 2;
|
||
for(i = 0; i < s->ntrail; i++){
|
||
v = &s->var[VAR(s->trail[i])];
|
||
if(!v->isbinreason && v->reason != nil)
|
||
nkeep++;
|
||
}
|
||
if(nkeep <= 0) return; /* shouldn't happen */
|
||
s->nfullrcfl = 0;
|
||
if(fullrun(s) < 0){ /* accidentally determined UNSAT during fullrun() */
|
||
free(s->fullrcfl);
|
||
s->fullrcfl = nil;
|
||
return;
|
||
}
|
||
ranges(s);
|
||
fullrconflicts(s);
|
||
j = judgement(s, nkeep);
|
||
execution(s, j);
|
||
rewatch(s);
|
||
}
|
||
|
||
/* to avoid getting stuck, flushing backs up the trail to remove low activity variables.
|
||
* don't worry about throwing out high activity ones, they'll get readded quickly. */
|
||
static void
|
||
theflush(SATSolve *s)
|
||
{
|
||
double actk;
|
||
int dd, l;
|
||
|
||
/* "reluctant doubling" wizardry to determine when to flush */
|
||
if((s->flushu & -s->flushu) == s->flushv){
|
||
s->flushu++;
|
||
s->flushv = 1;
|
||
s->flushθ = s->flushψ;
|
||
}else{
|
||
s->flushv *= 2;
|
||
s->flushθ += s->flushθ >> 4;
|
||
}
|
||
s->nextflush = s->conflicts + s->flushv;
|
||
if(s->agility > s->flushθ) return; /* don't flush when we're too busy */
|
||
/* clean up the heap so that a free variable is at the top */
|
||
while(s->nheap > 0 && s->heap[0]->lvl >= 0)
|
||
satheaptake(s);
|
||
if(s->nheap == 0) return; /* shouldn't happen */
|
||
actk = s->heap[0]->activity;
|
||
for(dd = 0; dd < s->lvl; dd++){
|
||
l = s->trail[s->decbd[dd+1]];
|
||
if(s->var[VAR(l)].activity < actk)
|
||
break;
|
||
}
|
||
satbackjump(s, dd);
|
||
}
|
||
|
||
int
|
||
satsolve(SATSolve *s)
|
||
{
|
||
int l;
|
||
SATClause *c;
|
||
uvlong b;
|
||
|
||
if(s == nil) return 1;
|
||
if(s->scratched) return -1;
|
||
if(s->nvar == 0) return 1;
|
||
solvinit(s);
|
||
|
||
while(!s->unsat){
|
||
re:
|
||
while(s->binptr < s->ntrail){
|
||
l = s->trail[s->binptr++];
|
||
b = binforcing(s, l, 0);
|
||
sanity(s);
|
||
if(b != 0){
|
||
if(s->lvl == 0) goto unsat;
|
||
conflict(s, nil, b, 0);
|
||
sanity(s);
|
||
}
|
||
}
|
||
while(s->forptr < s->ntrail){
|
||
l = s->trail[s->forptr++];
|
||
c = forcing(s, NOT(l), 0);
|
||
sanity(s);
|
||
if(c != nil){
|
||
if(s->lvl == 0) goto unsat;
|
||
conflict(s, c, 0, 0);
|
||
sanity(s);
|
||
}
|
||
}
|
||
if(s->binptr < s->ntrail) goto re;
|
||
if(s->ntrail == s->nvar) goto out;
|
||
if(s->conflicts >= s->nextpurge)
|
||
thepurge(s);
|
||
else if(s->conflicts >= s->nextflush)
|
||
theflush(s);
|
||
else
|
||
decision(s);
|
||
}
|
||
unsat:
|
||
s->unsat = 1;
|
||
out:
|
||
satcleanup(s, 0);
|
||
return !s->unsat;
|
||
}
|
||
|
||
void
|
||
satreset(SATSolve *s)
|
||
{
|
||
int i;
|
||
|
||
if(s == nil || s->decbd == nil) return;
|
||
satbackjump(s, -1);
|
||
s->lvl = 0;
|
||
for(i = 0; i < s->nvar; i++){
|
||
s->var[i].activity = 0;
|
||
s->var[i].flags |= VARPHASE;
|
||
}
|
||
satcleanup(s, 1);
|
||
s->Δactivity = 1;
|
||
s->Δclactivity = 1;
|
||
}
|