diff --git a/src/fast_cal/cal_core.cc b/src/fast_cal/cal_core.cc
index d2e1712..4380aed 100644
--- a/src/fast_cal/cal_core.cc
+++ b/src/fast_cal/cal_core.cc
@@ -37,8 +37,8 @@ void FastCal::new_case(uint64_t code, uint64_t mask) {
 }
 
 /// build total search tree
-void FastCal::build(const RawCode &code) {
-    auto core = init((uint64_t)code);
+void FastCal::build() {
+    auto core = init(root);
     /// start BFS search
     while (!cache.empty()) {
         core.next_cases(cache.front()->code, cache.front()->mask);
@@ -47,8 +47,8 @@ void FastCal::build(const RawCode &code) {
 }
 
 /// found first matched target
-RawCode FastCal::target(const RawCode &code, const match_t &match) {
-    auto core = init((uint64_t)code);
+RawCode FastCal::target(const match_t &match) {
+    auto core = init(root);
     /// start BFS search
     while (!cache.empty()) {
         if (match(cache.front()->code)) {
@@ -60,47 +60,47 @@ RawCode FastCal::target(const RawCode &code, const match_t &match) {
     return FC_NOT_FOUND; // target not found
 }
 
-/// found multi-targets matched in first same layer
-std::vector<RawCode> FastCal::target_multi(const RawCode &code, const match_t &match) {
-    auto core = init((uint64_t)code);
+/// found all of the furthest cases
+std::vector<RawCode> FastCal::furthest() {
+    auto core = init(root);
     auto layer_end = cache.back();
-    std::vector<RawCode> matched; // matched list
+    std::vector<RawCode> layer_cases;
     /// start BFS search
     while (!cache.empty()) {
-        if (match(cache.front()->code)) { // match target
-            matched.emplace_back(cache.front()->code);
-        }
         core.next_cases(cache.front()->code, cache.front()->mask);
+        layer_cases.emplace_back(
+            RawCode::unsafe_create(cache.front()->code) // record layer cases
+        );
         if (cache.front() == layer_end) { // reach layer ending
-            if (!matched.empty()) {
-                return matched; // stop at first matched layer
+            if (cache.size() == 1) {
+                break; // stop loop at last layer
             }
+            layer_cases.clear();
             layer_end = cache.back(); // reset layer ending
         }
         cache.pop();
     }
-    return std::vector<RawCode>{}; // no target found
+    return layer_cases; // release the latest layer cases
 }
 
-/// found all of the furthest cases
-std::vector<RawCode> FastCal::furthest(const RawCode &code) {
-    auto core = init((uint64_t)code);
+/// found multi-targets matched in first same layer
+std::vector<RawCode> FastCal::target_multi(const FastCal::match_t &match) {
+    auto core = init(root);
     auto layer_end = cache.back();
-    std::vector<RawCode> layer_cases;
+    std::vector<RawCode> matched; // matched list
     /// start BFS search
     while (!cache.empty()) {
+        if (match(cache.front()->code)) { // match target
+            matched.emplace_back(cache.front()->code);
+        }
         core.next_cases(cache.front()->code, cache.front()->mask);
-        layer_cases.emplace_back(
-            RawCode::unsafe_create(cache.front()->code) // record layer cases
-        );
         if (cache.front() == layer_end) { // reach layer ending
-            if (cache.size() == 1) {
-                break; // stop loop at last layer
+            if (!matched.empty()) {
+                return matched; // stop at first matched layer
             }
-            layer_cases.clear();
             layer_end = cache.back(); // reset layer ending
         }
         cache.pop();
     }
-    return layer_cases; // release latest layer cases
+    return std::vector<RawCode>{}; // no target found
 }
diff --git a/src/fast_cal/fast_cal.cc b/src/fast_cal/fast_cal.cc
index 9598786..1ea6fd2 100644
--- a/src/fast_cal/fast_cal.cc
+++ b/src/fast_cal/fast_cal.cc
@@ -4,17 +4,25 @@
 #include "fast_cal.h"
 #include "raw_code.h"
 
+FastCal::FastCal(const RawCode &code) {
+    this->root = (uint64_t)code;
+}
+
+void FastCal::set_root(const RawCode &code) {
+    this->root = (uint64_t)code;
+}
+
 /// klotski resolved -> 2x2 block at address 13 (aka 0xD)
 auto resolved = [](uint64_t code) {
     return ((code >> (3 * 0xD)) & 0b111) == B_2x2; // check 2x2 block address
 };
 
-RawCode FastCal::solve(const RawCode &code) {
-    return FastCal::target(code, resolved);
+RawCode FastCal::solve() {
+    return FastCal::target(resolved);
 }
 
-std::vector<RawCode> FastCal::solve_multi(const RawCode &code) {
-    return FastCal::target_multi(code, resolved);
+std::vector<RawCode> FastCal::solve_multi() {
+    return FastCal::target_multi(resolved);
 }
 
 std::vector<RawCode> FastCal::resolve(const RawCode &start) {
@@ -56,17 +64,17 @@ std::vector<RawCode> FastCal::backtrack(const RawCode &code) {
 
 /// static BFS search functions
 std::vector<std::vector<RawCode>> FastCal::to_furthest(const RawCode &start) {
-    auto fc = FastCal();
+    auto fc = FastCal(start);
     std::vector<std::vector<RawCode>> result;
-    for (const auto &furthest : fc.furthest(start)) {
+    for (const auto &furthest : fc.furthest()) {
         result.emplace_back(fc.backtrack(furthest)); // backtrack every furthest cases
     }
     return result;
 }
 
 std::vector<RawCode> FastCal::search(const RawCode &start, const match_t &match) {
-    auto fc = FastCal();
-    auto result = fc.target(start, match);
+    auto fc = FastCal(start);
+    auto result = fc.target(match);
     if (result == FC_NOT_FOUND) {
         return std::vector<RawCode>{}; // target not matched
     }
@@ -74,9 +82,9 @@ std::vector<RawCode> FastCal::search(const RawCode &start, const match_t &match)
 }
 
 std::vector<std::vector<RawCode>> FastCal::search_multi(const RawCode &start, const match_t &match) {
-    auto fc = FastCal();
+    auto fc = FastCal(start);
     std::vector<std::vector<RawCode>> result;
-    for (const auto &target : fc.target_multi(start, match)) {
+    for (const auto &target : fc.target_multi(match)) {
         result.emplace_back(fc.backtrack(target)); // backtrack every target
     }
     return result;
diff --git a/src/fast_cal/fast_cal.h b/src/fast_cal/fast_cal.h
index 1835aed..6967386 100644
--- a/src/fast_cal/fast_cal.h
+++ b/src/fast_cal/fast_cal.h
@@ -15,19 +15,21 @@ class FastCal {
 public:
     typedef std::function<bool(uint64_t)> match_t;
 
+    /// FastCal start case
+    void set_root(const RawCode &code);
+    explicit FastCal(const RawCode &code);
+
     /// backtrack functions
     int step_num(const RawCode &code);
     std::vector<RawCode> backtrack(const RawCode &code);
 
-    // TODO: should we using code as class member
-
     /// BFS search functions
-    void build(const RawCode &code);
-    RawCode solve(const RawCode &code);
-    std::vector<RawCode> furthest(const RawCode &code);
-    std::vector<RawCode> solve_multi(const RawCode &code);
-    RawCode target(const RawCode &code, const match_t &match);
-    std::vector<RawCode> target_multi(const RawCode &code, const match_t &match);
+    void build();
+    RawCode solve();
+    std::vector<RawCode> furthest();
+    std::vector<RawCode> solve_multi();
+    RawCode target(const match_t &match);
+    std::vector<RawCode> target_multi(const match_t &match);
 
     /// static BFS search functions
     static std::vector<RawCode> resolve(const RawCode &start);
@@ -43,6 +45,7 @@ private:
         fast_cal_t *last;
     };
 
+    uint64_t root;
     std::queue<fast_cal_t*> cache;
     std::unordered_map<uint64_t, fast_cal_t> cases;
 
diff --git a/src/main.cc b/src/main.cc
index 71aa55b..9bc5837 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -17,55 +17,50 @@ int main() {
 
     BasicRanges::build();
 
-//    std::vector<RawCode> test_cases;
-//    {
-//        AllCases::build();
-//        std::vector<uint64_t> all_cases;
-//        for (uint64_t head = 0; head < 16; ++head) {
-//            for (const auto &range : AllCases::fetch()[head]) {
-//                all_cases.emplace_back(head << 32 | range);
-//            }
-//        }
-//        for (uint32_t i = 0; i < 1000; ++i) {
-//            test_cases.emplace_back(
-//                RawCode::from_common_code(all_cases.at(i * 29334))
-//            );
-//        }
-//    }
-//    std::cout << "test size -> " << test_cases.size() << std::endl;
+    std::vector<RawCode> test_cases;
+    {
+        AllCases::build();
+        std::vector<uint64_t> all_cases;
+        for (uint64_t head = 0; head < 16; ++head) {
+            for (const auto &range : AllCases::fetch()[head]) {
+                all_cases.emplace_back(head << 32 | range);
+            }
+        }
+        for (uint32_t i = 0; i < 1000; ++i) {
+            test_cases.emplace_back(
+                RawCode::from_common_code(all_cases.at(i * 29334))
+            );
+        }
+    }
+    std::cout << "test size -> " << test_cases.size() << std::endl;
 
 
 //    std::cout << "wait 3s" << std::endl;
 //    sleep(3);
 
-//    std::cout << "start benchmark" << std::endl;
+    std::cout << "start benchmark" << std::endl;
     auto start_time = clock();
 
 //    AllCases::build();
 
 
-//    {
-//        auto fc = FastCal();
-//        for (uint32_t i = 0; i < test_cases.size(); ++i) {
-//            fc.solve(test_cases[i]);
-//            if (i % 1000 == 0) {
-//                std::cout << (i * 100 / test_cases.size()) << "%" << std::endl;
-//            }
-//        }
-//        for (auto code : test_cases) {
-//            fc.solve(code);
-//        }
-//    }
+    {
+        auto fc = FastCal(RawCode::unsafe_create(0));
+        for (auto code : test_cases) {
+            fc.set_root(code);
+            fc.solve();
+        }
+    }
 
 
-    auto a = Analyse();
+//    auto a = Analyse();
 //    a.build((uint64_t)RawCode::from_common_code("1a9bf0c"));
-    auto ret = a.build_until((uint64_t)RawCode::from_common_code("1a9bf0c"), [](uint64_t code) {
-        return ((code >> (3 * 0xD)) & 0b111) == B_2x2;
-    });
-    for (const auto &r : ret) {
-        std::cout << RawCode(r) << std::endl;
-    }
+//    auto ret = a.build_until((uint64_t)RawCode::from_common_code("1a9bf0c"), [](uint64_t code) {
+//        return ((code >> (3 * 0xD)) & 0b111) == B_2x2;
+//    });
+//    for (const auto &r : ret) {
+//        std::cout << RawCode(r) << std::endl;
+//    }
 
 //    auto raw_code = CommonCode("A5D3AF0").to_raw_code().unwrap();
 
@@ -104,11 +99,11 @@ int main() {
 //    std::cout << CommonCode::from_short_code("AXCZN") << std::endl;
 
 
-//    std::cerr << (clock() - start_time) / CLOCKS_PER_SEC << "s" << std::endl;
+    std::cerr << (clock() - start_time) / CLOCKS_PER_SEC << "s" << std::endl;
 //    std::cerr << (clock() - start_time) * 1000 / CLOCKS_PER_SEC << "ms" << std::endl;
-    std::cerr << (clock() - start_time) * 1000000 / CLOCKS_PER_SEC << "us" << std::endl;
+//    std::cerr << (clock() - start_time) * 1000000 / CLOCKS_PER_SEC << "us" << std::endl;
 
-//    std::cout << "complete benchmark" << std::endl;
+    std::cout << "complete benchmark" << std::endl;
 
 //    pause();