diff --git a/atpg b/atpg
index 6c33244..fcca67d 100755
Binary files a/atpg and b/atpg differ
diff --git a/circuit.cpp b/circuit.cpp
index aa9ef8b..8dea274 100644
--- a/circuit.cpp
+++ b/circuit.cpp
@@ -27,4 +27,57 @@ void Circuit::cal_topo_index() {
             }
         }
     }
+}
+
+int Circuit::cal_gate_value(const Gate* &gate) {
+    int res;
+
+    switch(gate->type) {
+        case Gate::NOT:
+            res = !gate->inputs[0]->value;
+            break;
+        case Gate::BUF:
+            res = gate->inputs[0]->value;
+            break;
+        case Gate::AND:
+            res = gate->inputs[0]->value;
+            for(int i=1; i<gate->inputs.size(); i++) {
+                res &= gate->inputs[i]->value;
+            }
+            break;
+        case Gate::NAND:
+            res = gate->inputs[0]->value;
+            for(int i=1; i<gate->inputs.size(); i++) {
+                res &= gate->inputs[i]->value;
+            }
+            res = !res;
+            break;
+        case Gate::OR:
+            res = gate->inputs[0]->value;
+            for(int i=1; i<gate->inputs.size(); i++) {
+                res |= gate->inputs[i]->value;
+            }
+            break;
+        case Gate::NOR:
+            res = gate->inputs[0]->value;
+            for(int i=1; i<gate->inputs.size(); i++) {
+                res |= gate->inputs[i]->value;
+            }
+            res = !res;
+            break;
+        case Gate::XOR:
+            res = gate->inputs[0]->value;
+            for(int i=1; i<gate->inputs.size(); i++) {
+                res ^= gate->inputs[i]->value;
+            }
+            break;
+        case Gate::XNOR:
+            res = gate->inputs[0]->value;
+            for(int i=1; i<gate->inputs.size(); i++) {
+                res ^= gate->inputs[i]->value;
+            }
+            res = !res;
+            break;
+    }
+    return res;
 }
\ No newline at end of file
diff --git a/circuit.h b/circuit.h
index a893714..64d4ff7 100644
--- a/circuit.h
+++ b/circuit.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include <string>
 #include <vector>
 #include <unordered_map>
@@ -6,8 +8,8 @@ class Gate {
 public:
     int topo;
     std::string name;
-    enum { AND, NAND, OR, NOR, XOR, XNOR, NOT, BUF, INPUT, OUTPUT } type;
-    enum { VAL_ZERO, VAL_ONE, VAL_X } value;
+    enum Type { AND, NAND, OR, NOR, XOR, XNOR, NOT, BUF, INPUT, OUTPUT } type;
+    int value;
     std::vector<Gate*> outputs;
     std::vector<Gate*> inputs;
 };
@@ -19,6 +21,7 @@ std::vector<Gate*> POs;
 std::vector<Gate*> gates;
 std::unordered_map<std::string, Gate*> name2gate;
 void parse_from_file(const char *filename);
+int cal_gate_value(const Gate* &gate);
 void cal_topo_index();
-void cal_headlines();
+
 };
\ No newline at end of file
diff --git a/ls.cpp b/ls.cpp
new file mode 100644
index 0000000..0471d53
--- /dev/null
+++ b/ls.cpp
@@ -0,0 +1,35 @@
+#include "ls.h"
+
+
+std::vector<int> local_search(Circuit* circuit) {
+
+    // local search vector
+    std::vector<Gate*> vec;
+
+    init_vector(circuit, &vec);
+
+    init_circuit(circuit);
+    
+    printf("local search!\n");
+
+    return std::vector<int>();
+}
+
+
+void init_circuit(Circuit* circuit) {
+    for(auto pi : circuit->PIs) {
+        pi->value = rand() % 2;
+    }
+}
+
+void init_vector(Circuit* circuit, std::vector<Gate*> *vec) {
+    for(auto pi : circuit->PIs) {
+        vec->push_back(pi);
+    }
+    for(auto gate : circuit->gates) {
+        // fanout stem
+        if(gate->outputs.size() >= 2) {
+            vec->push_back(gate);
+        }
+    }
+}
\ No newline at end of file
diff --git a/ls.h b/ls.h
new file mode 100644
index 0000000..270c45c
--- /dev/null
+++ b/ls.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "circuit.h"
+
+std::vector<int> local_search(Circuit* circuit);
+
+// private
+void init_circuit(Circuit* circuit);
+void init_vector(Circuit* circuit, std::vector<Gate*> *vec);
\ No newline at end of file
diff --git a/main.cpp b/main.cpp
index e1c8ad7..9954451 100644
--- a/main.cpp
+++ b/main.cpp
@@ -2,8 +2,8 @@
 #include <cstdlib>
 #include <assert.h>
 
-
 #include "circuit.h"
+#include "ls.h"
 
 int main(int args, char* argv[]) {
 
@@ -21,11 +21,22 @@ int main(int args, char* argv[]) {
     printf("PO:\t%ld\n", circuit.POs.size());
     printf("Gates:\t%ld\n", circuit.name2gate.size());
 
+    int cnt = 0;
+    for(auto& gate: circuit.gates) {
+        if(gate->outputs.size() > 2) {
+            cnt++;
+        }
+    }
+    printf("Stem:\t%d\n", cnt);
+
     printf("cal topo index ...\n");
     circuit.cal_topo_index();
     for(Gate* gate : circuit.gates) {
         assert(gate->topo > 0);
     }
 
+    srand(19260817);
+    local_search(&circuit);
+
     return 0;
 }
\ No newline at end of file
diff --git a/parser.cpp b/parser.cpp
index fe276e7..83f8f89 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -73,7 +73,6 @@ void Circuit::parse_from_file(const char *filename) {
 
             Gate* gate = new Gate();
             gate->name = tokens[0];
-            gate->value = Gate::VAL_X;
 
             for(auto &in : ins) {
                 if(!name2gate.count(in)) {
@@ -109,10 +108,9 @@ void Circuit::parse_from_file(const char *filename) {
             Gate* gate = new Gate();
             gate->name = tokens[2];
             gate->type = Gate::INPUT;
-            gate->value = Gate::VAL_X;
 
             name2gate.insert(std::make_pair(gate->name, gate));
-            gates.push_back(gate);
+            // gates.push_back(gate);
             PIs.push_back(gate);
         } 
         // gate