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 // SPDX-License-Identifier: MIT
 // Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
  
 #pragma once
  
 #ifndef CK_CODE_GEN_RTC
 #include <ostream>
 #endif
  
 #include "ck/utility/integral_constant.hpp"
 #include "ck/utility/type.hpp"
 #include "ck/utility/functional.hpp"
 #include "ck/utility/math.hpp"
  
 namespace ck {
  
 template <index_t, index_t, index_t>
 struct static_for;
  
 template <index_t...>
 struct Sequence;
  
 template <typename Seq, index_t I>
 struct sequence_split;
  
 template <typename>
 struct sequence_reverse;
  
 template <typename>
 struct sequence_map_inverse;
  
 template <typename>
 struct is_valid_sequence_map;
  
 template <index_t I, index_t... Is>
 __host__ __device__ constexpr auto sequence_pop_front(Sequence<I, Is...>);
  
 template <typename Seq>
 __host__ __device__ constexpr auto sequence_pop_back(Seq);
  
 template <index_t... Is>
 struct Sequence
 {
     using Type      = Sequence;
     using data_type = index_t;
  
     static constexpr index_t mSize = sizeof...(Is);
  
     __host__ __device__ static constexpr auto Size() { return Number<mSize>{}; }
  
     __host__ __device__ static constexpr auto GetSize() { return Size(); }
  
     __host__ __device__ static constexpr index_t At(index_t I)
     {
         // the last dummy element is to prevent compiler complain about empty array, when mSize = 0
         const index_t mData[mSize + 1] = {Is..., 0};
         return mData[I];
     }
  
     template <index_t I>
     __host__ __device__ static constexpr auto At(Number<I>)
     {
         static_assert(I < mSize, "wrong! I too large");
  
         return Number<At(I)>{};
     }
  
     template <index_t I>
     __host__ __device__ static constexpr auto Get(Number<I>)
     {
         return At(Number<I>{});
     }
  
     template <typename I>
     __host__ __device__ constexpr auto operator[](I i) const
     {
         return At(i);
     }
  
     template <index_t... IRs>
     __host__ __device__ static constexpr auto ReorderGivenNew2Old(Sequence<IRs...> /*new2old*/)
     {
         static_assert(sizeof...(Is) == sizeof...(IRs),
                       "wrong! reorder map should have the same size as Sequence to be rerodered");
  
         static_assert(is_valid_sequence_map<Sequence<IRs...>>::value, "wrong! invalid reorder map");
  
         return Sequence<Type::At(Number<IRs>{})...>{};
     }
  
     // MapOld2New is Sequence<...>
     template <typename MapOld2New>
     __host__ __device__ static constexpr auto ReorderGivenOld2New(MapOld2New)
     {
         static_assert(MapOld2New::Size() == Size(),
                       "wrong! reorder map should have the same size as Sequence to be rerodered");
  
         static_assert(is_valid_sequence_map<MapOld2New>::value, "wrong! invalid reorder map");
  
         return ReorderGivenNew2Old(typename sequence_map_inverse<MapOld2New>::type{});
     }
  
     __host__ __device__ static constexpr auto Reverse()
     {
         return typename sequence_reverse<Type>::type{};
     }
  
     __host__ __device__ static constexpr auto Front()
     {
         static_assert(mSize > 0, "wrong!");
         return At(Number<0>{});
     }
  
     __host__ __device__ static constexpr auto Back()
     {
         static_assert(mSize > 0, "wrong!");
         return At(Number<mSize - 1>{});
     }
  
     __host__ __device__ static constexpr auto PopFront() { return sequence_pop_front(Type{}); }
  
     __host__ __device__ static constexpr auto PopBack() { return sequence_pop_back(Type{}); }
  
     template <index_t... Xs>
     __host__ __device__ static constexpr auto PushFront(Sequence<Xs...>)
     {
         return Sequence<Xs..., Is...>{};
     }
  
     template <index_t... Xs>
     __host__ __device__ static constexpr auto PushFront(Number<Xs>...)
     {
         return Sequence<Xs..., Is...>{};
     }
  
     template <index_t... Xs>
     __host__ __device__ static constexpr auto PushBack(Sequence<Xs...>)
     {
         return Sequence<Is..., Xs...>{};
     }
  
     template <index_t... Xs>
     __host__ __device__ static constexpr auto PushBack(Number<Xs>...)
     {
         return Sequence<Is..., Xs...>{};
     }
  
     template <index_t... Ns>
     __host__ __device__ static constexpr auto Extract(Number<Ns>...)
     {
         return Sequence<Type::At(Number<Ns>{})...>{};
     }
  
     template <index_t... Ns>
     __host__ __device__ static constexpr auto Extract(Sequence<Ns...>)
     {
         return Sequence<Type::At(Number<Ns>{})...>{};
     }
  
     template <index_t I, index_t X>
     __host__ __device__ static constexpr auto Modify(Number<I>, Number<X>)
     {
         static_assert(I < Size(), "wrong!");
  
         using seq_split          = sequence_split<Type, I>;
         constexpr auto seq_left  = typename seq_split::left_type{};
         constexpr auto seq_right = typename seq_split::right_type{}.PopFront();
  
         return seq_left.PushBack(Number<X>{}).PushBack(seq_right);
     }
  
     template <typename F>
     __host__ __device__ static constexpr auto Transform(F f)
     {
         return Sequence<f(Is)...>{};
     }
  
     __host__ __device__ static void Print()
     {
         printf("{");
         printf("size %d, ", index_t{Size()});
         static_for<0, Size(), 1>{}([&](auto i) { printf("%d ", At(i).value); });
         printf("}");
     }
 };
  
 // merge sequence
 template <typename Seq, typename... Seqs>
 struct sequence_merge
 {
     using type = typename sequence_merge<Seq, typename sequence_merge<Seqs...>::type>::type;
 };
  
 template <index_t... Xs, index_t... Ys>
 struct sequence_merge<Sequence<Xs...>, Sequence<Ys...>>
 {
     using type = Sequence<Xs..., Ys...>;
 };
  
 template <typename Seq>
 struct sequence_merge<Seq>
 {
     using type = Seq;
 };
  
 // generate sequence
 template <index_t NSize, typename F>
 struct sequence_gen
 {
     template <index_t IBegin, index_t NRemain, typename G>
     struct sequence_gen_impl
     {
         static constexpr index_t NRemainLeft  = NRemain / 2;
         static constexpr index_t NRemainRight = NRemain - NRemainLeft;
         static constexpr index_t IMiddle      = IBegin + NRemainLeft;
  
         using type = typename sequence_merge<
             typename sequence_gen_impl<IBegin, NRemainLeft, G>::type,
             typename sequence_gen_impl<IMiddle, NRemainRight, G>::type>::type;
     };
  
     template <index_t I, typename G>
     struct sequence_gen_impl<I, 1, G>
     {
         static constexpr index_t Is = G{}(Number<I>{});
         using type                  = Sequence<Is>;
     };
  
     template <index_t I, typename G>
     struct sequence_gen_impl<I, 0, G>
     {
         using type = Sequence<>;
     };
  
     using type = typename sequence_gen_impl<0, NSize, F>::type;
 };
  
 // arithmetic sequence
 template <index_t IBegin, index_t IEnd, index_t Increment>
 struct arithmetic_sequence_gen
 {
     struct F
     {
         __host__ __device__ constexpr index_t operator()(index_t i) const
         {
             return i * Increment + IBegin;
         }
     };
  
     using type0 = typename sequence_gen<(IEnd - IBegin) / Increment, F>::type;
     using type1 = Sequence<>;
  
     static constexpr bool kHasContent =
         (Increment > 0 && IBegin < IEnd) || (Increment < 0 && IBegin > IEnd);
  
     using type = typename conditional<kHasContent, type0, type1>::type;
 };
  
 // uniform sequence
 template <index_t NSize, index_t I>
 struct uniform_sequence_gen
 {
     struct F
     {
         __host__ __device__ constexpr index_t operator()(index_t) const { return I; }
     };
  
     using type = typename sequence_gen<NSize, F>::type;
 };
  
 // reverse inclusive scan (with init) sequence
 template <typename, typename, index_t>
 struct sequence_reverse_inclusive_scan;
  
 template <index_t I, index_t... Is, typename Reduce, index_t Init>
 struct sequence_reverse_inclusive_scan<Sequence<I, Is...>, Reduce, Init>
 {
     using old_scan = typename sequence_reverse_inclusive_scan<Sequence<Is...>, Reduce, Init>::type;
  
     static constexpr index_t new_reduce = Reduce{}(I, old_scan{}.Front());
  
     using type = typename sequence_merge<Sequence<new_reduce>, old_scan>::type;
 };
  
 template <index_t I, typename Reduce, index_t Init>
 struct sequence_reverse_inclusive_scan<Sequence<I>, Reduce, Init>
 {
     using type = Sequence<Reduce{}(I, Init)>;
 };
  
 template <typename Reduce, index_t Init>
 struct sequence_reverse_inclusive_scan<Sequence<>, Reduce, Init>
 {
     using type = Sequence<>;
 };
  
 // split sequence
 template <typename Seq, index_t I>
 struct sequence_split
 {
     static constexpr index_t NSize = Seq{}.Size();
  
     using range0 = typename arithmetic_sequence_gen<0, I, 1>::type;
     using range1 = typename arithmetic_sequence_gen<I, NSize, 1>::type;
  
     using left_type  = decltype(Seq::Extract(range0{}));
     using right_type = decltype(Seq::Extract(range1{}));
 };
  
 // reverse sequence
 template <typename Seq>
 struct sequence_reverse
 {
     static constexpr index_t NSize = Seq{}.Size();
  
     using seq_split = sequence_split<Seq, NSize / 2>;
     using type      = typename sequence_merge<
         typename sequence_reverse<typename seq_split::right_type>::type,
         typename sequence_reverse<typename seq_split::left_type>::type>::type;
 };
  
 template <index_t I>
 struct sequence_reverse<Sequence<I>>
 {
     using type = Sequence<I>;
 };
  
 template <index_t I0, index_t I1>
 struct sequence_reverse<Sequence<I0, I1>>
 {
     using type = Sequence<I1, I0>;
 };
  
 #if 1
 template <typename Reduce, typename Seq, typename... Seqs>
 struct sequence_reduce
 {
     using type = typename sequence_reduce<Reduce,
                                           Seq,
                                           typename sequence_reduce<Reduce, Seqs...>::type>::type;
 };
  
 template <typename Reduce, index_t... Xs, index_t... Ys>
 struct sequence_reduce<Reduce, Sequence<Xs...>, Sequence<Ys...>>
 {
     using type = Sequence<Reduce{}(Xs, Ys)...>;
 };
  
 template <typename Reduce, typename Seq>
 struct sequence_reduce<Reduce, Seq>
 {
     using type = Seq;
 };
 #endif
  
 template <typename Values, typename Ids, typename Compare>
 struct sequence_sort_impl
 {
     template <typename LeftValues,
               typename LeftIds,
               typename RightValues,
               typename RightIds,
               typename MergedValues,
               typename MergedIds,
               typename Comp>
     struct sorted_sequence_merge_impl
     {
         static constexpr bool choose_left = LeftValues::Front() < RightValues::Front();
  
         static constexpr index_t chosen_value =
             choose_left ? LeftValues::Front() : RightValues::Front();
         static constexpr index_t chosen_id = choose_left ? LeftIds::Front() : RightIds::Front();
  
         using new_merged_values = decltype(MergedValues::PushBack(Number<chosen_value>{}));
         using new_merged_ids    = decltype(MergedIds::PushBack(Number<chosen_id>{}));
  
         using new_left_values =
             typename conditional<choose_left, decltype(LeftValues::PopFront()), LeftValues>::type;
         using new_left_ids =
             typename conditional<choose_left, decltype(LeftIds::PopFront()), LeftIds>::type;
  
         using new_right_values =
             typename conditional<choose_left, RightValues, decltype(RightValues::PopFront())>::type;
         using new_right_ids =
             typename conditional<choose_left, RightIds, decltype(RightIds::PopFront())>::type;
  
         using merge = sorted_sequence_merge_impl<new_left_values,
                                                  new_left_ids,
                                                  new_right_values,
                                                  new_right_ids,
                                                  new_merged_values,
                                                  new_merged_ids,
                                                  Comp>;
         // this is output
         using merged_values = typename merge::merged_values;
         using merged_ids    = typename merge::merged_ids;
     };
  
     template <typename LeftValues,
               typename LeftIds,
               typename MergedValues,
               typename MergedIds,
               typename Comp>
     struct sorted_sequence_merge_impl<LeftValues,
                                       LeftIds,
                                       Sequence<>,
                                       Sequence<>,
                                       MergedValues,
                                       MergedIds,
                                       Comp>
     {
         using merged_values = typename sequence_merge<MergedValues, LeftValues>::type;
         using merged_ids    = typename sequence_merge<MergedIds, LeftIds>::type;
     };
  
     template <typename RightValues,
               typename RightIds,
               typename MergedValues,
               typename MergedIds,
               typename Comp>
     struct sorted_sequence_merge_impl<Sequence<>,
                                       Sequence<>,
                                       RightValues,
                                       RightIds,
                                       MergedValues,
                                       MergedIds,
                                       Comp>
     {
         using merged_values = typename sequence_merge<MergedValues, RightValues>::type;
         using merged_ids    = typename sequence_merge<MergedIds, RightIds>::type;
     };
  
     template <typename LeftValues,
               typename LeftIds,
               typename RightValues,
               typename RightIds,
               typename Comp>
     struct sorted_sequence_merge
     {
         using merge = sorted_sequence_merge_impl<LeftValues,
                                                  LeftIds,
                                                  RightValues,
                                                  RightIds,
                                                  Sequence<>,
                                                  Sequence<>,
                                                  Comp>;
  
         using merged_values = typename merge::merged_values;
         using merged_ids    = typename merge::merged_ids;
     };
  
     static constexpr index_t nsize = Values::Size();
  
     using split_unsorted_values = sequence_split<Values, nsize / 2>;
     using split_unsorted_ids    = sequence_split<Ids, nsize / 2>;
  
     using left_unsorted_values = typename split_unsorted_values::left_type;
     using left_unsorted_ids    = typename split_unsorted_ids::left_type;
     using left_sort          = sequence_sort_impl<left_unsorted_values, left_unsorted_ids, Compare>;
     using left_sorted_values = typename left_sort::sorted_values;
     using left_sorted_ids    = typename left_sort::sorted_ids;
  
     using right_unsorted_values = typename split_unsorted_values::right_type;
     using right_unsorted_ids    = typename split_unsorted_ids::right_type;
     using right_sort = sequence_sort_impl<right_unsorted_values, right_unsorted_ids, Compare>;
     using right_sorted_values = typename right_sort::sorted_values;
     using right_sorted_ids    = typename right_sort::sorted_ids;
  
     using merged_sorted = sorted_sequence_merge<left_sorted_values,
                                                 left_sorted_ids,
                                                 right_sorted_values,
                                                 right_sorted_ids,
                                                 Compare>;
  
     using sorted_values = typename merged_sorted::merged_values;
     using sorted_ids    = typename merged_sorted::merged_ids;
 };
  
 template <index_t ValueX, index_t ValueY, index_t IdX, index_t IdY, typename Compare>
 struct sequence_sort_impl<Sequence<ValueX, ValueY>, Sequence<IdX, IdY>, Compare>
 {
     static constexpr bool choose_x = Compare{}(ValueX, ValueY);
  
     using sorted_values =
         typename conditional<choose_x, Sequence<ValueX, ValueY>, Sequence<ValueY, ValueX>>::type;
     using sorted_ids = typename conditional<choose_x, Sequence<IdX, IdY>, Sequence<IdY, IdX>>::type;
 };
  
 template <index_t Value, index_t Id, typename Compare>
 struct sequence_sort_impl<Sequence<Value>, Sequence<Id>, Compare>
 {
     using sorted_values = Sequence<Value>;
     using sorted_ids    = Sequence<Id>;
 };
  
 template <typename Compare>
 struct sequence_sort_impl<Sequence<>, Sequence<>, Compare>
 {
     using sorted_values = Sequence<>;
     using sorted_ids    = Sequence<>;
 };
  
 template <typename Values, typename Compare>
 struct sequence_sort
 {
     using unsorted_ids = typename arithmetic_sequence_gen<0, Values::Size(), 1>::type;
     using sort         = sequence_sort_impl<Values, unsorted_ids, Compare>;
  
     // this is output
     using type                = typename sort::sorted_values;
     using sorted2unsorted_map = typename sort::sorted_ids;
 };
  
 template <typename Values, typename Less, typename Equal>
 struct sequence_unique_sort
 {
     template <typename RemainValues,
               typename RemainIds,
               typename UniquifiedValues,
               typename UniquifiedIds,
               typename Eq>
     struct sorted_sequence_uniquify_impl
     {
         static constexpr index_t current_value = RemainValues::Front();
         static constexpr index_t current_id    = RemainIds::Front();
  
         static constexpr bool is_unique_value = (current_value != UniquifiedValues::Back());
  
         using new_remain_values = decltype(RemainValues::PopFront());
         using new_remain_ids    = decltype(RemainIds::PopFront());
  
         using new_uniquified_values =
             typename conditional<is_unique_value,
                                  decltype(UniquifiedValues::PushBack(Number<current_value>{})),
                                  UniquifiedValues>::type;
  
         using new_uniquified_ids =
             typename conditional<is_unique_value,
                                  decltype(UniquifiedIds::PushBack(Number<current_id>{})),
                                  UniquifiedIds>::type;
  
         using uniquify = sorted_sequence_uniquify_impl<new_remain_values,
                                                        new_remain_ids,
                                                        new_uniquified_values,
                                                        new_uniquified_ids,
                                                        Eq>;
  
         // this is output
         using uniquified_values = typename uniquify::uniquified_values;
         using uniquified_ids    = typename uniquify::uniquified_ids;
     };
  
     template <typename UniquifiedValues, typename UniquifiedIds, typename Eq>
     struct sorted_sequence_uniquify_impl<Sequence<>,
                                          Sequence<>,
                                          UniquifiedValues,
                                          UniquifiedIds,
                                          Eq>
     {
         using uniquified_values = UniquifiedValues;
         using uniquified_ids    = UniquifiedIds;
     };
  
     template <typename SortedValues, typename SortedIds, typename Eq>
     struct sorted_sequence_uniquify
     {
         using uniquify = sorted_sequence_uniquify_impl<decltype(SortedValues::PopFront()),
                                                        decltype(SortedIds::PopFront()),
                                                        Sequence<SortedValues::Front()>,
                                                        Sequence<SortedIds::Front()>,
                                                        Eq>;
  
         using uniquified_values = typename uniquify::uniquified_values;
         using uniquified_ids    = typename uniquify::uniquified_ids;
     };
  
     using sort          = sequence_sort<Values, Less>;
     using sorted_values = typename sort::type;
     using sorted_ids    = typename sort::sorted2unsorted_map;
  
     using uniquify = sorted_sequence_uniquify<sorted_values, sorted_ids, Equal>;
  
     // this is output
     using type                = typename uniquify::uniquified_values;
     using sorted2unsorted_map = typename uniquify::uniquified_ids;
 };
  
 template <typename SeqMap>
 struct is_valid_sequence_map : is_same<typename arithmetic_sequence_gen<0, SeqMap::Size(), 1>::type,
                                        typename sequence_sort<SeqMap, math::less<index_t>>::type>
 {
 };
  
 template <typename SeqMap>
 struct sequence_map_inverse
 {
     template <typename X2Y, typename WorkingY2X, index_t XBegin, index_t XRemain>
     struct sequence_map_inverse_impl
     {
         static constexpr auto new_y2x =
             WorkingY2X::Modify(X2Y::At(Number<XBegin>{}), Number<XBegin>{});
  
         using type =
             typename sequence_map_inverse_impl<X2Y, decltype(new_y2x), XBegin + 1, XRemain - 1>::
                 type;
     };
  
     template <typename X2Y, typename WorkingY2X, index_t XBegin>
     struct sequence_map_inverse_impl<X2Y, WorkingY2X, XBegin, 0>
     {
         using type = WorkingY2X;
     };
  
     using type =
         typename sequence_map_inverse_impl<SeqMap,
                                            typename uniform_sequence_gen<SeqMap::Size(), 0>::type,
                                            0,
                                            SeqMap::Size()>::type;
 };
  
 template <index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr bool operator==(Sequence<Xs...>, Sequence<Ys...>)
 {
     return ((Xs == Ys) && ...);
 }
  
 template <index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr auto operator+(Sequence<Xs...>, Sequence<Ys...>)
 {
     static_assert(sizeof...(Xs) == sizeof...(Ys), "wrong! inconsistent size");
  
     return Sequence<(Xs + Ys)...>{};
 }
  
 template <index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr auto operator-(Sequence<Xs...>, Sequence<Ys...>)
 {
     static_assert(sizeof...(Xs) == sizeof...(Ys), "wrong! inconsistent size");
  
     return Sequence<(Xs - Ys)...>{};
 }
  
 template <index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr auto operator*(Sequence<Xs...>, Sequence<Ys...>)
 {
     static_assert(sizeof...(Xs) == sizeof...(Ys), "wrong! inconsistent size");
  
     return Sequence<(Xs * Ys)...>{};
 }
  
 template <index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr auto operator/(Sequence<Xs...>, Sequence<Ys...>)
 {
     static_assert(sizeof...(Xs) == sizeof...(Ys), "wrong! inconsistent size");
  
     return Sequence<(Xs / Ys)...>{};
 }
  
 template <index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr auto operator%(Sequence<Xs...>, Sequence<Ys...>)
 {
     static_assert(sizeof...(Xs) == sizeof...(Ys), "wrong! inconsistent size");
  
     return Sequence<(Xs % Ys)...>{};
 }
  
 template <index_t... Xs, index_t Y>
 __host__ __device__ constexpr auto operator+(Sequence<Xs...>, Number<Y>)
 {
     return Sequence<(Xs + Y)...>{};
 }
  
 template <index_t... Xs, index_t Y>
 __host__ __device__ constexpr auto operator-(Sequence<Xs...>, Number<Y>)
 {
     return Sequence<(Xs - Y)...>{};
 }
  
 template <index_t... Xs, index_t Y>
 __host__ __device__ constexpr auto operator*(Sequence<Xs...>, Number<Y>)
 {
     return Sequence<(Xs * Y)...>{};
 }
  
 template <index_t... Xs, index_t Y>
 __host__ __device__ constexpr auto operator/(Sequence<Xs...>, Number<Y>)
 {
     return Sequence<(Xs / Y)...>{};
 }
  
 template <index_t... Xs, index_t Y>
 __host__ __device__ constexpr auto operator%(Sequence<Xs...>, Number<Y>)
 {
     return Sequence<(Xs % Y)...>{};
 }
  
 template <index_t Y, index_t... Xs>
 __host__ __device__ constexpr auto operator+(Number<Y>, Sequence<Xs...>)
 {
     return Sequence<(Y + Xs)...>{};
 }
  
 template <index_t Y, index_t... Xs>
 __host__ __device__ constexpr auto operator-(Number<Y>, Sequence<Xs...>)
 {
     return Sequence<(Y - Xs)...>{};
 }
  
 template <index_t Y, index_t... Xs>
 __host__ __device__ constexpr auto operator*(Number<Y>, Sequence<Xs...>)
 {
     return Sequence<(Y * Xs)...>{};
 }
  
 template <index_t Y, index_t... Xs>
 __host__ __device__ constexpr auto operator/(Number<Y>, Sequence<Xs...>)
 {
     return Sequence<(Y / Xs)...>{};
 }
  
 template <index_t Y, index_t... Xs>
 __host__ __device__ constexpr auto operator%(Number<Y>, Sequence<Xs...>)
 {
     return Sequence<(Y % Xs)...>{};
 }
  
 template <index_t I, index_t... Is>
 __host__ __device__ constexpr auto sequence_pop_front(Sequence<I, Is...>)
 {
     return Sequence<Is...>{};
 }
  
 template <typename Seq>
 __host__ __device__ constexpr auto sequence_pop_back(Seq)
 {
     static_assert(Seq::Size() > 0, "wrong! cannot pop an empty Sequence!");
     return sequence_pop_front(Seq::Reverse()).Reverse();
 }
  
 template <typename... Seqs>
 __host__ __device__ constexpr auto merge_sequences(Seqs...)
 {
     return typename sequence_merge<Seqs...>::type{};
 }
  
 template <typename F, index_t... Xs>
 __host__ __device__ constexpr auto transform_sequences(F f, Sequence<Xs...>)
 {
     return Sequence<f(Xs)...>{};
 }
  
 template <typename F, index_t... Xs, index_t... Ys>
 __host__ __device__ constexpr auto transform_sequences(F f, Sequence<Xs...>, Sequence<Ys...>)
 {
     static_assert(Sequence<Xs...>::mSize == Sequence<Ys...>::mSize, "Dim not the same");
  
     return Sequence<f(Xs, Ys)...>{};
 }
  
 template <typename F, index_t... Xs, index_t... Ys, index_t... Zs>
 __host__ __device__ constexpr auto
 transform_sequences(F f, Sequence<Xs...>, Sequence<Ys...>, Sequence<Zs...>)
 {
     static_assert(Sequence<Xs...>::mSize == Sequence<Ys...>::mSize &&
                       Sequence<Xs...>::mSize == Sequence<Zs...>::mSize,
                   "Dim not the same");
  
     return Sequence<f(Xs, Ys, Zs)...>{};
 }
  
 template <typename Seq, typename Reduce, index_t Init>
 __host__ __device__ constexpr auto reverse_inclusive_scan_sequence(Seq, Reduce, Number<Init>)
 {
     return typename sequence_reverse_inclusive_scan<Seq, Reduce, Init>::type{};
 }
  
 template <typename Seq, typename Reduce, index_t Init>
 __host__ __device__ constexpr auto reverse_exclusive_scan_sequence(Seq, Reduce, Number<Init>)
 {
     return reverse_inclusive_scan_sequence(Seq::PopFront(), Reduce{}, Number<Init>{})
         .PushBack(Number<Init>{});
 }
  
 template <typename Seq, typename Reduce, index_t Init>
 __host__ __device__ constexpr auto inclusive_scan_sequence(Seq, Reduce, Number<Init>)
 {
     return reverse_inclusive_scan_sequence(Seq{}.Reverse(), Reduce{}, Number<Init>{}).Reverse();
 }
  
 template <typename Seq, index_t... Is>
 __host__ __device__ constexpr auto pick_sequence_elements_by_ids(Seq, Sequence<Is...> /* ids */)
 {
     return Sequence<Seq::At(Number<Is>{})...>{};
 }
  
 #if 1
 namespace detail {
 template <typename WorkSeq, typename RemainSeq, typename RemainMask>
 struct pick_sequence_elements_by_mask_impl
 {
     using new_work_seq = typename conditional<RemainMask::Front(),
                                               decltype(WorkSeq::PushBack(RemainSeq::Front())),
                                               WorkSeq>::type;
  
     using type =
         typename pick_sequence_elements_by_mask_impl<new_work_seq,
                                                      decltype(RemainSeq::PopFront()),
                                                      decltype(RemainMask::PopFront())>::type;
 };
  
 template <typename WorkSeq>
 struct pick_sequence_elements_by_mask_impl<WorkSeq, Sequence<>, Sequence<>>
 {
     using type = WorkSeq;
 };
  
 } // namespace detail
  
 template <typename Seq, typename Mask>
 __host__ __device__ constexpr auto pick_sequence_elements_by_mask(Seq, Mask)
 {
     static_assert(Seq::Size() == Mask::Size(), "wrong!");
  
     return typename detail::pick_sequence_elements_by_mask_impl<Sequence<>, Seq, Mask>::type{};
 }
  
 namespace detail {
 template <typename WorkSeq, typename RemainValues, typename RemainIds>
 struct modify_sequence_elements_by_ids_impl
 {
     using new_work_seq = decltype(WorkSeq::Modify(RemainIds::Front(), RemainValues::Front()));
  
     using type =
         typename modify_sequence_elements_by_ids_impl<new_work_seq,
                                                       decltype(RemainValues::PopFront()),
                                                       decltype(RemainIds::PopFront())>::type;
 };
  
 template <typename WorkSeq>
 struct modify_sequence_elements_by_ids_impl<WorkSeq, Sequence<>, Sequence<>>
 {
     using type = WorkSeq;
 };
 } // namespace detail
  
 template <typename Seq, typename Values, typename Ids>
 __host__ __device__ constexpr auto modify_sequence_elements_by_ids(Seq, Values, Ids)
 {
     static_assert(Values::Size() == Ids::Size() && Seq::Size() >= Values::Size(), "wrong!");
  
     return typename detail::modify_sequence_elements_by_ids_impl<Seq, Values, Ids>::type{};
 }
 #endif
  
 template <typename Seq, typename Reduce, index_t Init>
 __host__ __device__ constexpr index_t
 reduce_on_sequence(Seq, Reduce f, Number<Init> /*initial_value*/)
 {
     index_t result = Init;
  
     for(index_t i = 0; i < Seq::Size(); ++i)
     {
         result = f(result, Seq::At(i));
     }
  
     return result;
 }
  
 // TODO: a generic any_of for any container
 template <typename Seq, typename F>
 __host__ __device__ constexpr bool sequence_any_of(Seq, F f)
 {
     bool flag = false;
  
     for(index_t i = 0; i < Seq::Size(); ++i)
     {
         flag = flag || f(Seq::At(i));
     }
  
     return flag;
 }
  
 // TODO: a generic all_of for any container
 template <typename Seq, typename F>
 __host__ __device__ constexpr bool sequence_all_of(Seq, F f)
 {
     bool flag = true;
  
     for(index_t i = 0; i < Seq::Size(); ++i)
     {
         flag = flag && f(Seq::At(i));
     }
  
     return flag;
 }
  
 template <typename Sx, typename Sy>
 using sequence_merge_t = typename sequence_merge<Sx, Sy>::type;
  
 template <index_t NSize, index_t I>
 using uniform_sequence_gen_t = typename uniform_sequence_gen<NSize, I>::type;
  
 } // namespace ck
  
 #ifndef CK_CODE_GEN_RTC
 template <ck::index_t... Is>
 std::ostream& operator<<(std::ostream& os, const ck::Sequence<Is...>)
 {
     using S = ck::Sequence<Is...>;
     os << "{";
     ck::static_for<0, S::Size() - ck::Number<1>{}, 1>{}(
         [&](auto i) { os << S::At(i).value << ", "; });
     os << S::At(S::Size() - ck::Number<1>{}).value << "}";
     return os;
 }
 #endif