Commit 16b70566 authored by Timo Teräs's avatar Timo Teräs

solver: additional backjumping scheme

Enabled when all attempts to satisfy a name failed, we know that we
can ignore all decisions until we find a decision affecting the name
we wanted to satisfy.
parent 01d0e4c4
......@@ -40,6 +40,7 @@ struct apk_solver_name_state {
unsigned none_excluded : 1;
unsigned name_touched : 1;
unsigned preferred_chosen : 1;
unsigned backjump_enabled : 1;
};
#endif
......@@ -921,6 +921,7 @@ static solver_result_t push_decision(struct apk_solver_state *ss,
static int next_branch(struct apk_solver_state *ss)
{
unsigned int backup_until = ss->num_decisions;
struct apk_name *backjump_name = NULL;
while (ss->num_decisions > 0) {
struct apk_decision *d = &ss->decisions[ss->num_decisions];
......@@ -928,6 +929,11 @@ static int next_branch(struct apk_solver_state *ss)
undo_decision(ss, d);
/* If we undoed constraints on the backjump name, we
* cannot backjump on it anymore. */
if (backjump_name && !backjump_name->ss.backjump_enabled)
backjump_name = NULL;
#ifdef DEBUG_CHECKS
ASSERT(cmpscore(&d->saved_score, &ss->score) == 0,
"Saved_score "SCORE_FMT" != score "SCORE_FMT,
......@@ -938,20 +944,32 @@ static int next_branch(struct apk_solver_state *ss)
name->name, d->saved_requirers, name->ss.requirers);
#endif
if (backup_until >= ss->num_decisions &&
if ((backjump_name == NULL || backjump_name == d->name) &&
backup_until >= ss->num_decisions &&
d->branching_point == BRANCH_YES) {
d->branching_point = BRANCH_NO;
d->type = (d->type == DECISION_ASSIGN) ? DECISION_EXCLUDE : DECISION_ASSIGN;
return apply_decision(ss, d);
} else {
if (d->branching_point == BRANCH_YES)
} else if (d->branching_point == BRANCH_YES) {
if (backup_until < ss->num_decisions)
dbg_printf("skipping %s, %d < %d\n",
name->name, backup_until, ss->num_decisions);
else if (backjump_name != NULL && backjump_name != d->name)
dbg_printf("backjumping to find new assign candidate for %s\n",
backjump_name->name);
}
/* Back jump to find assign candidate for this name */
if (d->name->ss.backjump_enabled && backjump_name == NULL)
backjump_name = d->name;
/* When undoing the initial "exclude none" decision, check if
* we can backjump. */
if (d->has_package == 0 && !d->found_solution) {
if (backjump_name == d->name) {
d->name->ss.backjump_enabled = 0;
backjump_name = NULL;
}
if (d->backup_until && backup_until > d->backup_until)
backup_until = d->backup_until;
}
......@@ -1022,7 +1040,7 @@ static void apply_constraint(struct apk_solver_state *ss, struct apk_dependency
ps0->conflicts);
changed |= 1;
} else if (requirer_pkg != NULL) {
dbg_printf(PKG_VER_FMT ": inheriting flags and pinning from"PKG_VER_FMT"\n",
dbg_printf(PKG_VER_FMT ": inheriting flags and pinning from "PKG_VER_FMT"\n",
PKG_VER_PRINTF(pkg0),
PKG_VER_PRINTF(requirer_pkg));
changed |= inherit_package_state(ss->db, pkg0, requirer_pkg);
......@@ -1090,6 +1108,7 @@ static void undo_constraint(struct apk_solver_state *ss, struct apk_dependency *
ps0->conflicts--;
else
ps0->unsatisfied--;
pkg0->name->ss.backjump_enabled = 0;
dbg_printf(PKG_VER_FMT ": conflicts-- -> %d\n",
PKG_VER_PRINTF(pkg0),
ps0->conflicts);
......@@ -1132,6 +1151,9 @@ static int reconsider_name(struct apk_solver_state *ss, struct apk_name *name)
SCORE_PRINTF(&ss->best_score));
return push_decision(ss, name, NULL, DECISION_EXCLUDE, BRANCH_NO, FALSE);
}
name->ss.backjump_enabled = 0;
return push_decision(ss, name, NULL, DECISION_EXCLUDE, BRANCH_YES, FALSE);
}
for (i = 0; i < name->providers->num; i++) {
......@@ -1151,17 +1173,23 @@ static int reconsider_name(struct apk_solver_state *ss, struct apk_name *name)
if (!p00->name->ss.locked)
continue;
if (p00->name->ss.chosen.version != &apk_null_blob ||
p00->version != &apk_null_blob)
break;
p00->version != &apk_null_blob) {
dbg_printf("reconsider_name: "PKG_VER_FMT": pruning due to provides (%s) conflict\n",
PKG_VER_PRINTF(pkg0), p00->name->name);
return push_decision(ss, name, pkg0, DECISION_EXCLUDE, BRANCH_NO, FALSE);
}
}
if (j < pkg0->provides->num)
continue;
score_locked = get_topology_score(ss, pkg0, &pkg0_score);
/* viable alternative? */
if (cmpscore2(&ss->score, &pkg0_score, &ss->best_score) >= 0)
if (cmpscore2(&ss->score, &pkg0_score, &ss->best_score) >= 0) {
dbg_printf("reconsider_name: "PKG_VER_FMT": pruning due to score "SCORE_FMT"+"SCORE_FMT">="SCORE_FMT"\n",
PKG_VER_PRINTF(pkg0),
SCORE_PRINTF(&ss->score), SCORE_PRINTF(&pkg0_score),
SCORE_PRINTF(&ss->best_score));
return push_decision(ss, name, pkg0, DECISION_EXCLUDE, BRANCH_NO, FALSE);
}
if (cmpscore(&pkg0_score, &best_score) < 0) {
best_score = pkg0_score;
......@@ -1180,14 +1208,19 @@ static int reconsider_name(struct apk_solver_state *ss, struct apk_name *name)
/* no options left */
if (options == 0) {
name->ss.backjump_enabled = 1;
if (name->ss.none_excluded) {
dbg_printf("reconsider_name: %s: no options pruning branch\n",
name->name);
return SOLVERR_PRUNED;
}
dbg_printf("reconsider_name: %s: no options locking none\n",
name->name);
if (name->ss.none_excluded)
return SOLVERR_PRUNED;
return push_decision(ss, name, NULL, DECISION_ASSIGN, BRANCH_NO, FALSE);
} else if (options == 1 && score_locked && name->ss.none_excluded && name == next_p->pkg->name) {
dbg_printf("reconsider_name: %s: only one choice left with known score, locking.\n",
name->name);
name->ss.backjump_enabled = 1;
return push_decision(ss, name, next_p->pkg, DECISION_ASSIGN, BRANCH_NO, FALSE);
}
......@@ -1258,11 +1291,14 @@ static int expand_branch(struct apk_solver_state *ss)
primary_decision = DECISION_ASSIGN;
else
primary_decision = DECISION_EXCLUDE;
name->ss.backjump_enabled = 0;
return push_decision(ss, name, NULL, primary_decision, BRANCH_YES, FALSE);
}
if (!can_install) {
/* provides with no version; not eglible to auto install */
dbg_printf("expand_branch: "PKG_VER_FMT" not installable. excluding.",
PKG_VER_PRINTF(pkg0));
return push_decision(ss, pkg0->name, pkg0, DECISION_EXCLUDE, BRANCH_NO, TRUE);
}
......@@ -1326,6 +1362,7 @@ static void record_solution(struct apk_solver_state *ss)
unsigned short pinning;
unsigned int repos;
name->ss.backjump_enabled = 0;
d->found_solution = 1;
if (pkg == NULL) {
......
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