diff --git a/atpg b/atpg
index b11a201..f104823 100755
Binary files a/atpg and b/atpg differ
diff --git a/circuit.h b/circuit.h
index e8c48ed..019e7e0 100644
--- a/circuit.h
+++ b/circuit.h
@@ -19,8 +19,6 @@ public:
     bool isPI;
     bool isPO;
 
-    std::unordered_map<Gate*, std::pair<int, int>> sa_by_out;
-
     std::vector<Gate*> pre_stems;
     std::vector<Gate*> suc_stems;
 
@@ -29,6 +27,7 @@ public:
 
     bool is_propagated();
     int cal_value();
+    bool cal_sa(bool x);
 };
 
 class Fault {
diff --git a/gate.cpp b/gate.cpp
index f5be4bd..c12ffe1 100644
--- a/gate.cpp
+++ b/gate.cpp
@@ -6,6 +6,32 @@ bool Gate::is_propagated() {
     return sa[0] || sa[1];
 }
 
+bool Gate::cal_sa(bool x) {
+    if(isPO) {
+        if(x == 0) return value;
+        else return !value;
+    }
+
+    bool sa0 = 0;
+    bool sa1 = 0;
+
+    for(Gate* out : outputs) {
+        if(!out->is_propagated()) continue;
+
+        if(out->cal_value() != out->value) continue;
+
+        this->value = !this->value;
+        bool detect = out->cal_value() != out->value;
+        this->value = !this->value;
+        if(!detect) continue;
+
+        sa0 |= this->value;
+        sa1 |= !this->value;
+    }
+    if(x == 0) return sa0;
+    else return sa1;
+}
+
 int Gate::cal_value() {
     int res;
 
diff --git a/ls.cpp b/ls.cpp
index b34a949..938d250 100644
--- a/ls.cpp
+++ b/ls.cpp
@@ -402,12 +402,32 @@ void Circuit::ls_block_recal(Gate* stem) {
             stem_satisfied[stem->id] = true;
             stem_total_weight -= stem_weight[stem->id];
             stem_total_cnt += 1;
+
+            for(Gate* pre : stem->pre_stems) {
+                if(flip_need_update[pre->id]) continue;
+
+                flip_need_update[pre->id] = true;
+                flip_update_queue.push_back(pre);
+
+                flip_total_weight += flip_weight[pre->id];
+                flip_total_cnt += 1;
+            }
         }
     
         if(stem->cal_value() != stem->value && stem_satisfied[stem->id]) {
             stem_satisfied[stem->id] = false;
             stem_total_weight += stem_weight[stem->id];
             stem_total_cnt -= 1;
+
+            for(Gate* pre : stem->pre_stems) {
+                if(flip_need_update[pre->id]) continue;
+
+                flip_need_update[pre->id] = true;
+                flip_update_queue.push_back(pre);
+
+                flip_total_weight += flip_weight[pre->id];
+                flip_total_cnt += 1;
+            }
         }
     }
 
@@ -417,27 +437,14 @@ void Circuit::ls_block_recal(Gate* stem) {
 
         used[g] = false;
 
-        bool right_value = (g->cal_value() == g->value);
         for(Gate* in : g->inputs) {
-            in->value = !in->value;
-            bool input_detected = (g->cal_value() != g->value);
-            in->value = !in->value;
-                
-            bool sa0 = right_value && input_detected && g->sa[!g->value] && in->value;
-            bool sa1 = right_value && input_detected && g->sa[!g->value] && !in->value;
-
-            in->sa_by_out[g] = std::make_pair(sa0, sa1);
 
             bool old_sa[2];
             old_sa[0] = in->sa[0];
             old_sa[1] = in->sa[1];
 
-            in->sa[0] = in->sa[1] = 0;
-            for(Gate* out : in->outputs) {
-                auto &p = in->sa_by_out[out];
-                in->sa[0] |= p.first;
-                in->sa[1] |= p.second;
-            }
+            in->sa[0] = in->cal_sa(0);
+            in->sa[1] = in->cal_sa(1);
 
             if(in->stem && !in->isPI && (in->sa[0] != old_sa[0] || in->sa[1] != old_sa[1])) {