General 2D Reduction Kernel (#2535)

* General 2D Reduction Kernel

* Move the reduction kernel from the example
* Split the code and add the necessary policy, problem, shape files as
per ck_tile convention
* Add/modify the headers
* Modified the example to work with the 'new' kernel
* Added tests for the kernel
* N-D refernce reduce
* Added support for N-D input with transform to 2D
* Added padding to support various input sized tensors
* Bug fix in the thread buffer constructor
* Some comments to explain the reduce2d block kernel

* comments resolution

* clang-format

* comments resolution

* clang-format

* clang-format

* comments resolution

* clang-format

include/ck_tile/ops/reduce/pipeline/reduce2d_default_policy.hpp

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
+
+#pragma once
+
+#include "ck_tile/core.hpp"
+#include "ck_tile/ops/reduce/block/block_reduce2d_problem.hpp"
+#include "ck_tile/ops/reduce/block/block_reduce2d.hpp"
+
+namespace ck_tile {
+
+struct Reduce2dDefaultPolicy
+{
+    template <typename Problem>
+    CK_TILE_DEVICE static constexpr auto MakeXBlockTileDistribution()
+    {
+        using S = typename Problem::BlockShape;
+        return make_static_tile_distribution(
+            tile_distribution_encoding<
+                sequence<>,
+                tuple<
+                    sequence<S::Repeat_M, S::WarpPerBlock_M, S::ThreadPerWarp_M, S::ThreadTile_M>,
+                    sequence<S::Repeat_N, S::WarpPerBlock_N, S::ThreadPerWarp_N, S::ThreadTile_N>>,
+                tuple<sequence<1, 2>, sequence<1, 2>>,
+                tuple<sequence<1, 1>, sequence<2, 2>>,
+                sequence<1, 1, 2, 2>,
+                sequence<0, 3, 0, 3>>{});
+    }
+
+    template <typename Problem>
+    CK_TILE_HOST_DEVICE static constexpr auto GetBlockReduce2d()
+    {
+        using P_ = BlockReduce2dProblem<typename Problem::XDataType,
+                                        typename Problem::ComputeDataType,
+                                        typename Problem::BlockShape>;
+        return BlockReduce2d<P_>{};
+    }
+
+    template <typename Problem>
+    CK_TILE_HOST_DEVICE static constexpr auto GetBlockReduce2dSync()
+    {
+        using P_ = BlockReduce2dProblem<typename Problem::XDataType,
+                                        typename Problem::ComputeDataType,
+                                        typename Problem::BlockShape>;
+        return BlockReduce2dSync<P_>{};
+    }
+
+    template <typename Problem>
+    CK_TILE_HOST_DEVICE static constexpr auto GetBlockReduce2dCrossWarpSync()
+    {
+        using P_ = BlockReduce2dProblem<typename Problem::XDataType,
+                                        typename Problem::ComputeDataType,
+                                        typename Problem::BlockShape>;
+        return BlockReduce2dCrossWarpSync<P_>{};
+    }
+
+    template <typename Problem>
+    CK_TILE_HOST_DEVICE static constexpr index_t GetSmemSize()
+    {
+        if constexpr(Problem::kNeedCrossWarpSync)
+        {
+            using P_ = BlockReduce2dProblem<typename Problem::XDataType,
+                                            typename Problem::ComputeDataType,
+                                            typename Problem::BlockShape>;
+
+            using block_reduce2d = BlockReduce2d<P_>;
+            using x_block_tile =
+                decltype(make_static_distributed_tensor<typename Problem::XDataType>(
+                    MakeXBlockTileDistribution<Problem>()));
+            using y_block_tile = decltype(block_reduce2d::template MakeYBlockTile<x_block_tile>());
+
+            return GetBlockReduce2dCrossWarpSync<Problem>().template GetSmemSize<y_block_tile>();
+        }
+        else
+        {
+            return 1; // zero size arrays are an extension
+        }
+    }
+};
+} // namespace ck_tile

include/ck_tile/ops/reduce/pipeline/reduce2d_problem.hpp

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
+
+#pragma once
+
+#include "ck_tile/core.hpp"
+
+namespace ck_tile {
+
+template <typename XDataType_,
+          typename ComputeDataType_,
+          typename YDataType_,
+          typename BlockShape_,
+          typename ReduceOp_>
+struct Reduce2dProblem
+{
+    using XDataType       = remove_cvref_t<XDataType_>;
+    using ComputeDataType = remove_cvref_t<ComputeDataType_>;
+    using YDataType       = remove_cvref_t<YDataType_>;
+    using BlockShape      = remove_cvref_t<BlockShape_>;
+    using ReduceOp        = ReduceOp_;
+
+    static constexpr bool kNeedCrossLaneSync = BlockShape::ThreadPerWarp_N > 1;
+    static constexpr bool kNeedCrossWarpSync = BlockShape::WarpPerBlock_N > 1;
+};
+
+} // namespace ck_tile

include/ck_tile/ops/reduce/pipeline/reduce2d_shape.hpp

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
+
+#pragma once
+
+#include "ck_tile/core.hpp"
+
+namespace ck_tile {
+
+template <typename BlockWarps, // num warps along seq<M, N>
+          typename BlockTile,  // block size, seq<M, N>
+          typename WarpTile,   // warp size, seq<M, N>
+          typename ThreadTile> // contiguous pixels(vector size) along seq<M, N>
+struct Reduce2dShape
+{
+    static constexpr index_t Block_M = BlockTile::at(number<0>{});
+    static constexpr index_t Block_N = BlockTile::at(number<1>{});
+
+    static constexpr index_t Warp_M = WarpTile::at(number<0>{});
+    static constexpr index_t Warp_N = WarpTile::at(number<1>{});
+
+    static constexpr index_t ThreadTile_M = ThreadTile::at(number<0>{});
+    static constexpr index_t ThreadTile_N = ThreadTile::at(number<1>{});
+
+    static constexpr index_t WarpPerBlock_M = BlockWarps::at(number<0>{});
+    static constexpr index_t WarpPerBlock_N = BlockWarps::at(number<1>{});
+
+    static constexpr index_t ThreadPerWarp_M = Warp_M / ThreadTile_M;
+    static constexpr index_t ThreadPerWarp_N = Warp_N / ThreadTile_N;
+
+    static constexpr index_t Repeat_M = Block_M / (WarpPerBlock_M * Warp_M);
+    static constexpr index_t Repeat_N = Block_N / (WarpPerBlock_N * Warp_N);
+
+    static constexpr index_t BlockSize =
+        ck_tile::get_warp_size() * reduce_on_sequence(BlockWarps{}, multiplies{}, number<1>{});
+};
+} // namespace ck_tile