diff --git a/src/klotski_core/ffi/tmain.cc b/src/klotski_core/ffi/tmain.cc
index 221b982..e4150a7 100644
--- a/src/klotski_core/ffi/tmain.cc
+++ b/src/klotski_core/ffi/tmain.cc
@@ -37,6 +37,8 @@ void tmain() {
 
 //    auto start = clock();
 
+    GroupCase::demo();
+
 //    auto ret = GroupCase::encode(CommonCode(0x1A9BF0C00));
 //    auto ret = GroupCase::encode(CommonCode(0x4FEA13400));
 //
diff --git a/src/klotski_core/group/group.h b/src/klotski_core/group/group.h
index e1b1ea9..3787331 100644
--- a/src/klotski_core/group/group.h
+++ b/src/klotski_core/group/group.h
@@ -162,6 +162,8 @@ public:
         uint32_t group_index;
     };
 
+    static void demo();
+
     /// Get the CommonCode using the group info.
     static CommonCode parse(const info_t &info);
 
diff --git a/src/klotski_core/group/group_info.cc b/src/klotski_core/group/group_info.cc
index bc57661..36390c6 100644
--- a/src/klotski_core/group/group_info.cc
+++ b/src/klotski_core/group/group_info.cc
@@ -2,6 +2,8 @@
 #include "group.h"
 #include "type_id.h"
 
+#include <iostream>
+
 namespace klotski {
 
 /// --------------------------------------- Group Type ----------------------------------------
@@ -66,4 +68,56 @@ GroupCase::info_t GroupCase::encode(const CommonCode &common_code) noexcept {
     };
 }
 
+/// ------------------------------------- Group Case Fast -------------------------------------
+
+void GroupCase::demo() {
+    std::cout << "ok" << std::endl;
+
+    // short code -> group_id + group_index
+
+    std::vector<uint32_t> group_info(SHORT_CODE_LIMIT);
+    std::vector<std::vector<ShortCode>> group_data[TYPE_ID_LIMIT];
+
+    ShortCode::speed_up(ShortCode::FAST);
+
+    auto convert = [](const std::vector<RawCode> &raw_codes) -> std::vector<CommonCode> {
+        return {raw_codes.begin(), raw_codes.end()};
+    };
+
+    for (uint32_t type_id = 0; type_id < TYPE_ID_LIMIT; ++type_id) {
+        auto tid = GroupType(type_id);
+
+        group_data[type_id].resize(tid.group_num());
+
+        for (uint32_t group_id = 0; group_id < tid.group_num(); ++group_id) {
+            auto group = Group(tid, group_id);
+
+            auto cases = convert(group.cases());
+            std::sort(cases.begin(), cases.end());
+
+            for (uint32_t group_index = 0; group_index < cases.size(); ++group_index) {
+                auto short_code = cases[group_index].to_short_code();
+                group_info[short_code.unwrap()] = (group_id << 20) | group_index;
+                group_data[type_id][group_id].emplace_back(short_code);
+            }
+        }
+        std::cerr << type_id << std::endl;
+    }
+
+
+    std::cout << group_data[169][1][7472].to_common_code() << std::endl;
+    std::cout << group_data[164][0][30833].to_common_code() << std::endl;
+
+    auto src_1 = CommonCode(0x1A9BF0C00);
+    auto tmp_1 = group_info[src_1.to_short_code().unwrap()];
+    std::cout << GroupType(src_1).unwrap() << "-"
+        << (tmp_1 >> 20) << "-" << (tmp_1 & 0xFFFFF) << std::endl;
+
+    auto src_2 = CommonCode(0x4FEA13400);
+    auto tmp_2 = group_info[src_2.to_short_code().unwrap()];
+    std::cout << GroupType(src_2).unwrap() << "-"
+        << (tmp_2 >> 20) << "-" << (tmp_2 & 0xFFFFF) << std::endl;
+
+}
+
 } // namespace klotski