1. 分析函数所涉及seen[v]使用
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传播实例：求解过程演示_10.48.640112774.cn中的一段输出
1 decisions: 25; decision var: -2
2 the size of trail is 28. : 1 -6 -27 -2 -22 -23 -20 -13 -10 -28 25 29 14 7 -3 18 -4 16 17 -9
5 24 11 12 -8 21 -15 26
3 the size of trail_lim is 2 : 1 3
4 the implied lit is : -22
5 the implied clause is: [-22 2 27 ]
6 the implied lit is : -23
7 the implied clause is: [-23 22 6 ]
8 the implied lit is : -20
9 the implied clause is: [-20 23 -1 ]
10 the implied lit is : -13
11 the implied clause is: [-13 20 2 ]
12 the implied lit is : -10
13 the implied clause is: [-10 20 6 ]
14 the implied lit is : -28
15 the implied clause is: [-28 13 20 ]
16 the implied lit is : 25
17 the implied clause is: [25 10 2 ]
18 the implied lit is : 29
19 the implied clause is: [29 28 27 ]
20 the implied lit is : 14
21 the implied clause is: [14 28 27 ]
22 the implied lit is : 7
23 the implied clause is: [7 -25 ]
24 the implied lit is : -3
25 the implied clause is: [-3 -25 ]
26 the implied lit is : 18
27 the implied clause is: [18 -25 2 ]
28 the implied lit is : -4
29 the implied clause is: [-4 -14 -29 ]
30 the implied lit is : 16
31 the implied clause is: [16 -14 -1 ]
32 the implied lit is : 17
33 the implied clause is: [17 -14 10 ]
34 the implied lit is : -9
35 the implied clause is: [-9 -14 10 ]
36 the implied lit is : 5
37 the implied clause is: [5 -7 28 ]
38 the implied lit is : 24
39 the implied clause is: [24 -7 13 ]
40 the implied lit is : 11
41 the implied clause is: [11 -7 22 ]
42 the implied lit is : 12
43 the implied clause is: [12 -7 23 ]
44 the implied lit is : -8
45 the implied clause is: [-8 -7 9 ]
46 the implied lit is : 21
47 the implied clause is: [21 3 -1 ]
48 the implied lit is : -15
49 the implied clause is: [-15 3 28 ]
50 the implied lit is : 26
51 the implied clause is: [26 -18 -29 ]
52
53 the conflict index of trail is : 16
54 the conflict liter is : -4
55 the tow clauses get confliction each other-----
56 the conflict reason clause is: [-4 -14 -29 ]
57 the confl clause is: [-21 4 -14 ]
58
59 the learnt clause is : [ 2 6 ]
60
61 backtrack_level:1
62
63 decisions: 26; decision var: 2
64 the size of trail is 16. : 1 -6 -27 2 -29 -7 28 -23 -25 19 10 -26 -18 -20 -14 24
65 the size of trail_lim is 1 : 1
66 the implied lit is : -29
67 the implied clause is: [-29 -2 6 ]
68 the implied lit is : -7
69 the implied clause is: [-7 -2 -1 ]
70 the implied lit is : 28
71 the implied clause is: [28 29 27 ]
72 the implied lit is : -23
73 the implied clause is: [7 -23 ]
74 the implied lit is : -25
75 the implied clause is: [7 -25 ]
76 the implied lit is : 19
77 the implied clause is: [7 19 ]
78 the implied lit is : 10
79 the implied clause is: [10 7 -2 ]
80 the implied lit is : -26
81 the implied clause is: [-26 -28 23 ]
82 the implied lit is : -18
83 the implied clause is: [-18 23 -2 ]
84 the implied lit is : -20
85 the implied clause is: [-20 23 -1 ]
86 the implied lit is : -14
87 the implied clause is: [-14 23 29 ]
88 the implied lit is : 24
89 the implied clause is: [24 -10 29 ]
90
91 the conflict index of trail is : 10
92 the conflict liter is : 10
93 the tow clauses get confliction each other-----
94 the conflict reason clause is: [10 7 -2 ]
95 the confl clause is: [20 -10 6 ]
96
97 the learnt clause is : [ 6 ]
98
99 backtrack_level:0
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上述传播遇到冲突之后进行冲突分析代码如下：
1 void Solver::analyze(CRef confl, vec<Lit>& out_learnt, int& out_btlevel, int& out_lbd)
2 {
3 int pathC = 0;
4 Lit p = lit_Undef;
5
6 // Generate conflict clause:
7 out_learnt.push(); // (leave room for the asserting literal)
8 int index = trail.size() - 1;
9 int nDecisionLevel = level(var(ca[confl][0]));
10 assert(nDecisionLevel == level(var(ca[confl][0])));
11
12 do{
13 assert(confl != CRef_Undef); // (otherwise should be UIP)
14 Clause& c = ca[confl];
15
16 // For binary clauses, we don't rearrange literals in propagate(),
17 // so check and make sure the first is an implied lit.
18 if (p != lit_Undef && c.size() == 2 && value(c[0]) == l_False){
19 assert(value(c[1]) == l_True);
20 Lit tmp = c[0];
21 c[0] = c[1], c[1] = tmp; }
22
23 for (int j = (p == lit_Undef) ? 0 : 1; j < c.size(); j++){
24 Lit q = c[j];
25
26 if (!seen[var(q)] && level(var(q)) > 0){
27 if (VSIDS){
28 varBumpActivity(var(q), .5);
29 add_tmp.push(q); //收集参与冲突的文字
30 }else
31 conflicted[var(q)]++;
32 seen[var(q)] = 1;
33 if (level(var(q)) >= nDecisionLevel){
34 pathC++;
35 }else
36 out_learnt.push(q);
37 }
38 }
39
40 // Select next clause to look at:
41 do {
42 while (!seen[var(trail[index--])]);
43 p = trail[index+1];
44 } while (level(var(p)) < nDecisionLevel);
45
46 confl = reason(var(p));
47 seen[var(p)] = 0;
48 pathC--;
49
50 }while (pathC > 0);
51 out_learnt[0] = ~p;
52
53
54 out_learnt.copyTo(analyze_toclear);
55
56 // Simplify conflict clause:
57
58 // Try further minimization?
59
60 // Recompute LBD if minimized.
61
62 // Find correct backtrack level:
63
64 for (int j = 0; j < analyze_toclear.size(); j++) seen[var(analyze_toclear[j])] = 0;
65 // ('seen[]' is now cleared)
66 }
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演示学习子句生成过程如下，注意seen[v]可见性。
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2. 冲突支配路径长度计算中所涉及seen[v]使用
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// pathCs[k] is the number of variables assigned at level k,
// it is initialized to 0 at the begining and reset to 0 after the function execution
bool Solver::collectFirstUIP(CRef confl){
involved_lits.clear();
int max_level=1;
Clause& c = ca[confl];
int minLevel = decisionLevel();
for(int i=0; i<c.size(); i++) {
Var v = var(c[i]);
// assert(!seen[v]);
if (level(v)>0) {
seen[v] = 1;
var_iLevel_tmp[v] = 1;
pathCs[level(v)]++;
if (minLevel>level(v)) {
minLevel=level(v);
assert(minLevel>0);
}
// varBumpActivity(v);
}
}
int limit=trail_lim[minLevel-1];
for(int i=trail.size()-1; i>=limit; i--) {
Lit p=trail[i]; Var v=var(p);
if (seen[v]) {
int currentDecLevel=level(v);
// if (currentDecLevel==decisionLevel())
// varBumpActivity(v);
seen[v]=0;
if (--pathCs[currentDecLevel]!=0) {
Clause& rc=ca[reason(v)];
int reasonVarLevel = var_iLevel_tmp[v] + 1;
if(reasonVarLevel>max_level) max_level = reasonVarLevel;
if (rc.size()==2 && value(rc[0])==l_False) {
// Special case for binary clauses
// The first one has to be SAT
assert(value(rc[1]) != l_False);
Lit tmp = rc[0];
rc[0] = rc[1], rc[1] = tmp;
}
for (int j = 1; j < rc.size(); j++){
Lit q = rc[j]; Var v1=var(q);
if (level(v1) > 0) {
if (minLevel>level(v1)) {
minLevel=level(v1);
limit=trail_lim[minLevel-1]; assert(minLevel>0);
}
if (seen[v1]) {
if (var_iLevel_tmp[v1]<reasonVarLevel)
var_iLevel_tmp[v1]=reasonVarLevel;
}
else {
var_iLevel_tmp[v1]=reasonVarLevel;
// varBumpActivity(v1);
seen[v1] = 1;
pathCs[level(v1)]++;
}
}
}
}
involved_lits.push(p);
}
}
double inc = var_iLevel_inc;
.....
}
代码运行完毕，seen[v]回复到不可见。
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