diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 217af06..dd29134 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -27,6 +27,7 @@ set(KLOTSKI_CORE_SRC
         group/internal/group.cc
         group/internal/group_pro.cc
         group/internal/group_cases.cc
+        group/internal/group_cases_pro.cc
 
         ranges/internal/spawn.cc
         ranges/internal/ranges.cc
diff --git a/src/core/group/group.h b/src/core/group/group.h
index 93360d8..8369e77 100644
--- a/src/core/group/group.h
+++ b/src/core/group/group.h
@@ -272,6 +272,23 @@ public:
     static std::vector<codec::RawCode> extend(codec::RawCode raw_code, uint32_t reserve = 0);
 };
 
+class GroupCasesPro {
+public:
+    struct CaseInfo {
+        GroupPro group;
+        uint32_t case_id;
+    };
+
+    // TODO: allow cal Group directly
+
+    static void build();
+
+    static codec::CommonCode fast_parse(CaseInfo info);
+
+    static CaseInfo fast_obtain(codec::ShortCode short_code);
+
+};
+
 class GroupCases {
 public:
     // TODO: rename as Info and changed as class
diff --git a/src/core/group/internal/group_cases_pro.cc b/src/core/group/internal/group_cases_pro.cc
new file mode 100644
index 0000000..2d7bd61
--- /dev/null
+++ b/src/core/group/internal/group_cases_pro.cc
@@ -0,0 +1,121 @@
+#include <iostream>
+
+#include "group/group.h"
+
+using klotski::codec::ShortCode;
+using klotski::codec::CommonCode;
+
+using klotski::cases::GroupPro;
+using klotski::cases::GroupUnion;
+using klotski::cases::RangesUnion;
+using klotski::cases::GroupCasesPro;
+
+using klotski::cases::ALL_GROUP_NUM;
+using klotski::cases::TYPE_ID_LIMIT;
+using klotski::cases::ALL_CASES_NUM_;
+
+struct case_info_t {
+    uint32_t pattern_id : 10;
+    uint32_t toward_id : 2;
+    uint32_t case_id  : 20;
+};
+
+static_assert(sizeof(case_info_t) == 4);
+
+// TODO: we need multi-thread support (Executor)
+
+static std::vector<std::vector<RangesUnion>> *ru_data = nullptr;
+static std::vector<case_info_t> *rev_data = nullptr;
+
+std::vector<std::vector<RangesUnion>> build_ranges_unions() {
+    std::vector<std::vector<RangesUnion>> unions;
+    unions.reserve(ALL_GROUP_NUM);
+
+    // TODO: add white list for single-group unions
+
+    for (uint32_t type_id = 0; type_id < TYPE_ID_LIMIT; ++type_id) {
+        auto group_union = GroupUnion::unsafe_create(type_id);
+        for (uint32_t pattern_id = 0; pattern_id < group_union.pattern_num(); ++pattern_id) {
+            std::vector<GroupPro> groups;
+            for (auto group : group_union.groups_pro()) {
+                if (group.pattern_id() == pattern_id) {
+                    groups.emplace_back(group);
+                }
+            }
+
+            std::vector<RangesUnion> tmp {4};
+            for (auto group : groups) {
+                tmp[group.mirror_toward()] = group.cases();
+            }
+            unions.emplace_back(tmp);
+        }
+    }
+    return unions;
+}
+
+static std::vector<case_info_t> build_tmp_data() {
+    std::vector<case_info_t> data;
+    data.resize(ALL_CASES_NUM_);
+    ShortCode::speed_up(true);
+
+    for (uint32_t type_id = 0; type_id < TYPE_ID_LIMIT; ++type_id) {
+        auto group_union = GroupUnion::unsafe_create(type_id);
+        for (auto group : group_union.groups_pro()) {
+            uint32_t pattern_id = group.pattern_id();
+            uint32_t toward_id = group.mirror_toward();
+
+            // TODO: batch mirror base on pattern
+            auto codes = group.cases().codes();
+            for (uint32_t case_id = 0; case_id < codes.size(); ++case_id) {
+                auto short_code = codes[case_id].to_short_code();
+                data[short_code.unwrap()] = case_info_t {
+                    .pattern_id = pattern_id,
+                    .toward_id = toward_id,
+                    .case_id = case_id,
+                };
+            }
+        }
+    }
+    return data;
+}
+
+void GroupCasesPro::build() {
+    static auto data_1 = build_ranges_unions();
+    static auto data_2 = build_tmp_data();
+    ru_data = &data_1;
+    rev_data = &data_2;
+}
+
+CommonCode GroupCasesPro::fast_parse(CaseInfo info) {
+
+    auto flat_id = PATTERN_OFFSET[info.group.type_id()] + info.group.pattern_id();
+
+    auto &cases = (*ru_data)[flat_id][info.group.mirror_toward()];
+    // TODO: make offset table for perf
+
+    uint64_t head = 0;
+
+    for (;;) {
+        if (info.case_id >= cases[head].size()) {
+            info.case_id -= cases[head].size();
+            ++head;
+        } else {
+            break;
+        }
+    }
+
+    auto range = cases[head][info.case_id];
+    return CommonCode::unsafe_create(head << 32 | range);
+}
+
+GroupCasesPro::CaseInfo GroupCasesPro::fast_obtain(codec::ShortCode short_code) {
+    uint16_t type_id = GroupUnion::from_short_code(short_code).unwrap(); // NOTE: need to convert as CommonCode
+    uint16_t pattern_id = (*rev_data)[short_code.unwrap()].pattern_id;
+    uint16_t toward_id = (*rev_data)[short_code.unwrap()].toward_id;
+    auto case_id = (*rev_data)[short_code.unwrap()].case_id;
+
+    return CaseInfo {
+        .group = GroupPro::unsafe_create(type_id, pattern_id, toward_id),
+        .case_id = case_id,
+    };
+}
diff --git a/src/core/main.cc b/src/core/main.cc
index fbf5365..5b9137e 100644
--- a/src/core/main.cc
+++ b/src/core/main.cc
@@ -30,6 +30,7 @@ using klotski::cases::Group;
 using klotski::cases::GroupPro;
 using klotski::cases::GroupCases;
 using klotski::cases::GroupUnion;
+using klotski::cases::GroupCasesPro;
 
 using klotski::cases::TYPE_ID_LIMIT;
 using klotski::cases::ALL_CASES_NUM_;
@@ -43,22 +44,30 @@ int main() {
 
     const auto start = std::chrono::system_clock::now();
 
-    ShortCode::speed_up(true);
-
-    std::unordered_set<RawCode> data_r;
-    std::unordered_set<ShortCode> data_s;
-    std::unordered_set<CommonCode> data_c;
-    data_r.reserve(ALL_CASES_NUM_);
-    data_s.reserve(ALL_CASES_NUM_);
-    data_c.reserve(ALL_CASES_NUM_);
-    for (auto code : AllCases::instance().fetch().codes()) {
-        data_c.emplace(code);
-        data_r.emplace(code.to_raw_code());
-        data_s.emplace(code.to_short_code());
-    }
-    std::cout << data_r.size() << std::endl;
-    std::cout << data_s.size() << std::endl;
-    std::cout << data_c.size() << std::endl;
+//    ShortCode::speed_up(true);
+//
+//    std::unordered_set<RawCode> data_r;
+//    std::unordered_set<ShortCode> data_s;
+//    std::unordered_set<CommonCode> data_c;
+//    data_r.reserve(ALL_CASES_NUM_);
+//    data_s.reserve(ALL_CASES_NUM_);
+//    data_c.reserve(ALL_CASES_NUM_);
+//    for (auto code : AllCases::instance().fetch().codes()) {
+//        data_c.emplace(code);
+//        data_r.emplace(code.to_raw_code());
+//        data_s.emplace(code.to_short_code());
+//    }
+//    std::cout << data_r.size() << std::endl;
+//    std::cout << data_s.size() << std::endl;
+//    std::cout << data_c.size() << std::endl;
+
+    GroupCasesPro::build();
+
+    auto kk = GroupCasesPro::fast_obtain(CommonCode::unsafe_create(0x1A9BF0C00).to_short_code());
+    std::cout << std::format("{}-{}-{}-{}", kk.group.type_id(), kk.group.pattern_id(), kk.group.mirror_toward(), kk.case_id) << std::endl;
+
+    auto code = GroupCasesPro::fast_parse(kk);
+    std::cout << code << std::endl;
 
 //    const auto common_code = CommonCode::unsafe_create(0x1A9BF0C00);
 //    const auto group = Group::from_common_code(common_code);