Development mirror of Jussi Rintanen’s planner Madagascar https://research.ics.aalto.fi/software/sat/madagascar/
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/* 2012 (C) Jussi Rintanen, jrintanen.jr@gmail.com */
/* For every literal l1, identify unit-propagation consequences l2 for which
the derivation involve non-binary clauses. These consequences l1 !-UP l2
are useful for two reasons.
1. It is not necessarily the case that -l2 !-UP -l1, and hence with
the new clause -l1 V l2 we get l2 !-UP l1 as a new consequence.
2. The clause learning algorithm avoids the use of a potentially long
non-binary clauses, sometimes leading to much shorter learned clauses
and much faster learning and unit propagation.
*/
#define noHARDDEBUG
#define noSHOWIT
void shortcutprobe(satinstance sati,int l) {
int i,l2;
PTRINT reason;
#ifdef HARDDEBUG
printf("--------------------------------------------------------------\n");
#endif
for(i=0;i<sati->nOfVars;i++) {
int flag;
flag=0;
if(!varunsetp(sati,i)) {
printf("INCORRECTLY ALREADY SET: %i",i); printTlit(sati,PLIT(i));
flag = 1;
}
assert(flag==0);
}
setUPstacktop(sati,-1); /* Drop the input unit clauses from the stack. */
sati->dlevel = 0;
sati->declevels[0] = 0;
#ifdef HARDDEBUG
printf("Trying ");
printTlit(sati,l);
printf("\n");
#endif
simpleaddtoqueue(sati,l,REASON_DECISION,0);
if(propagate(sati)) {
// Literal cannot be true.
#ifdef SHOWIT
printf("CONTRADICTION WITH ");
printTlit(sati,l);
printf("\n");
#endif
undo_assignments_until_level_NOHEAP(sati,0);
return;
}
// printf("PROPAGATED\n");
for(i=1;i<sati->endunitstack;i++) { // Go through inferred literals.
l2 = sati->unitstack[i];
reason = LITREASON(l2);
#ifdef HARDDEBUG
printf("Checking %i:",i); printTlit(sati,l2);
printf(" REASON: ");
if(reason == REASON_INPUT) printf("INPUT");
else if(reason == REASON_DECISION) printf("DECISION");
else if((reason&1)==0) printf(" LONG CLAUSE");
else printTlit(sati,reason >> 1);
printf("\n");
#endif
if((reason & 3) == 0 && clauselen((int *)reason) > 3) { // Reason is a long clause?
// Store the new binary literal for later use.
if(nofshortcutclauses+1 >= maxshortcutclauses) {
maxshortcutclauses = maxshortcutclauses * 2;
shortcutclauses = (shortcutclause *)realloc(shortcutclauses,
maxshortcutclauses * sizeof(shortcutclause));
}
shortcutclauses[nofshortcutclauses].l1 = NEG(l) % (2 * sati->nOfVarsPerTime);
shortcutclauses[nofshortcutclauses].l2 = l2 % (2 * sati->nOfVarsPerTime);
shortcutclauses[nofshortcutclauses++].tdiff = tvartime(sati,VAR(l2))-tvartime(sati,VAR(l));
#ifdef SHOWIT
printf("INFER CLAUSE: ");
printTlit(sati,shortcutclauses[nofshortcutclauses-1].l1);
printf(" V ");
printlit(shortcutclauses[nofshortcutclauses-1].l2);
printf("@%i (through length %i)\n",shortcutclauses[nofshortcutclauses-1].tdiff,clauselen((int *)reason));
#endif
}
}
undo_assignments_until_level_NOHEAP(sati,0);
for(i=0;i<sati->nOfVars;i++)
if(!varunsetp(sati,i)) {
printf("INCORRECTLY REMAINS SET: %i",i); printTlit(sati,PLIT(i));
assert(1==0);
}
}
void shortcuts(satinstance sati) {
int p;
maxshortcutclauses = 100000;
nofshortcutclauses = 0;
shortcutclauses = (shortcutclause *)malloc(maxshortcutclauses * sizeof(shortcutclause));
for(p=0;p<sati->nOfSVars;p++) {
shortcutprobe(sati,PLIT(varwithtime(sati,p,flagShortCutHorizon)));
shortcutprobe(sati,NLIT(varwithtime(sati,p,flagShortCutHorizon)));
}
#ifdef SHOWIT
printf("INFERRED %i SHORTCUT CLAUSES.\n",nofshortcutclauses);
#endif
}