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composable_kernel/include/ck_tile/ops/reduce/kernel/reduce2d_kernel.hpp

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// Copyright (c) Advanced Micro Devices, Inc., or its affiliates.
// SPDX-License-Identifier: MIT
#pragma once
#include "ck_tile/core.hpp"
#include "ck_tile/ops/common.hpp"
#include "ck_tile/ops/reduce/block/block_reduce.hpp"
#include "ck_tile/ops/reduce/pipeline/reduce2d_default_policy.hpp"
// Reduce2d Kernel:
// =======================================
// This kernel implements a 2D reduction operation that reduces data along the second dimension
// of a matrix. The reduction is performed in multiple hierarchical stages.
namespace ck_tile {
template <typename Problem_, typename Policy_ = Reduce2dDefaultPolicy>
struct Reduce
{
using Problem = ck_tile::remove_cvref_t<Problem_>;
using Policy = ck_tile::remove_cvref_t<Policy_>;
using XDataType = ck_tile::remove_cvref_t<typename Problem::XDataType>;
using ComputeDataType = ck_tile::remove_cvref_t<typename Problem::ComputeDataType>;
using YDataType = ck_tile::remove_cvref_t<typename Problem::YDataType>;
static constexpr index_t kBlockSize = Problem::BlockShape::BlockSize;
CK_TILE_HOST static constexpr auto BlockSize()
{
return is_wave32() ? kBlockSize / 2 : kBlockSize;
}
private:
// Helper function to calculate optimal vector size for input tensor
template <typename InputShape, typename ReduceDims>
static constexpr index_t CalculateInputVectorSize()
{
using S = typename Problem::BlockShape;
constexpr index_t memory_vector_size = 16 / sizeof(XDataType);
constexpr index_t thread_tile_vector_size = S::ThreadTile_N;
// Check if innermost reduce dimension is the last dimension (stride 1).
constexpr auto innermost_reduce_dim = ReduceDims{}.at(number<ReduceDims{}.size() - 1>{});
constexpr bool is_innermost_contiguous = (innermost_reduce_dim == InputShape{}.size() - 1);
// If innermost reduce dimension is not the last dim (not contiguous), limit vectorization
constexpr index_t stride_based_vector_size =
is_innermost_contiguous ? ck_tile::min(memory_vector_size, thread_tile_vector_size) : 1;
return stride_based_vector_size;
}
// Helper function to calculate optimal vector size for output tensor
static constexpr index_t CalculateOutputVectorSize()
{
using S = typename Problem::BlockShape;
constexpr index_t memory_vector_size = 16 / sizeof(YDataType);
constexpr index_t thread_tile_vector_size = S::ThreadTile_M;
constexpr index_t vector_size = ck_tile::min(memory_vector_size, thread_tile_vector_size);
return vector_size;
}
public:
template <typename InputShape, typename InputStrides, typename KeptDim, typename ReduceDims>
CK_TILE_DEVICE void operator()(const XDataType* p_x,
YDataType* p_y,
InputShape input_shape,
InputStrides input_strides,
KeptDim kept_dim,
ReduceDims reduce_dims) const
{
using S = typename Problem::BlockShape;
const auto iM = get_block_id() * S::Block_M;
static_assert(kept_dim.size() + reduce_dims.size() == InputShape::size(),
"Size of kept dimensions + reduced dimensions must equal input tensor rank");
// Extract lengths based on kept and reduced dimensions
const auto kept_lens = [&]() {
return generate_tuple([&](auto I) { return input_shape.at(number<kept_dim.at(I)>{}); },
number<kept_dim.size()>{});
}();
const auto reduce_lens = [&]() {
return generate_tuple(
[&](auto I) { return input_shape.at(number<reduce_dims.at(I)>{}); },
number<reduce_dims.size()>{});
}();
const auto kept_merge_transform = make_merge_transform(kept_lens);
const auto reduce_merge_transform = make_merge_transform(reduce_lens);
auto reduce_func = typename Problem::ReduceOp{};
const XDataType custom_padding_value =
type_convert<XDataType>(reduce_func.template GetIdentityValue<ComputeDataType>());
// Calculate optimal vector size for input tensor
constexpr auto x_tensor_vector_size = CalculateInputVectorSize<InputShape, ReduceDims>();
// Create input tensor view with custom padding value
auto desc = make_naive_tensor_descriptor(
input_shape, input_strides, number<x_tensor_vector_size>{}, number<1>{});
// Create buffer view with custom padding value
auto buffer_view = make_buffer_view<address_space_enum::global>(
p_x, desc.get_element_space_size(), custom_padding_value);
// Create tensor view with custom padding
const auto x_tensor = tensor_view<decltype(buffer_view), decltype(desc)>{buffer_view, desc};
const auto transformed_x_tensor = pad_tensor_view(
transform_tensor_view(x_tensor,
make_tuple(kept_merge_transform, reduce_merge_transform),
make_tuple(kept_dim, reduce_dims),
make_tuple(sequence<0>{}, sequence<1>{})),
make_tuple(number<S::Block_M>{}, number<S::Block_N>{}),
sequence<0, 1>{});
// Calculate strides for output tensor based on its own dimensions
const auto kept_strides = [&]() {
return generate_tuple(
[&](auto I) {
// Calculate stride for dimension I as product of all following dimensions
index_t stride = 1;
static_for<I + 1, kept_dim.size(), 1>{}(
[&](auto J) { stride *= kept_lens.at(number<J>{}); });
return stride;
},
number<kept_dim.size()>{});
}();
// Calculate optimal vector size for output tensor
constexpr auto y_tensor_vector_size = CalculateOutputVectorSize();
const auto y_m = make_naive_tensor_view<address_space_enum::global>(
p_y, kept_lens, kept_strides, number<y_tensor_vector_size>{}, number<1>{});
// Transform output tensor to 1D merged view
// This creates a view compatible with the 2D reduction pattern
const auto y_merged = transform_tensor_view(
y_m,
make_tuple(kept_merge_transform),
make_tuple(typename arithmetic_sequence_gen<0, kept_dim.size(), 1>::type{}),
make_tuple(sequence<0>{}));
auto x_window = make_tile_window(transformed_x_tensor,
make_tuple(number<S::Block_M>{}, number<S::Block_N>{}),
{iM, 0},
Policy::template MakeXBlockTileDistribution<Problem>());
auto y_window = make_tile_window(y_merged, make_tuple(number<S::Block_M>{}), {iM});
__shared__ char smem[Policy::template GetSmemSize<Problem>()];
// Get the merged dimension size from the transformed tensor
const auto merged_reduce_len =
transformed_x_tensor.get_tensor_descriptor().get_lengths().at(number<1>{});
index_t num_n_tile_iteration =
amd_wave_read_first_lane(integer_divide_ceil(merged_reduce_len, S::Block_N));
auto block_reduce2d = Policy::template GetBlockReduce2d<Problem>();
auto block_reduce2d_sync = Policy::template GetBlockReduce2dSync<Problem>();
auto block_reduce2d_cross_warp_sync =
Policy::template GetBlockReduce2dCrossWarpSync<Problem>();
using XTensorType = decltype(load_tile(x_window));
auto y_compute = block_reduce2d.template MakeYBlockTile<XTensorType>();
set_tile(y_compute, reduce_func.template GetIdentityValue<ComputeDataType>());
for(int iN = amd_wave_read_first_lane(0); iN < num_n_tile_iteration; ++iN)
{
const auto x = load_tile(x_window);
block_reduce2d(x, y_compute, reduce_func);
move_tile_window(x_window, {0, S::Block_N});
}
block_reduce2d_sync(y_compute, reduce_func);
block_reduce2d_cross_warp_sync(y_compute, smem, reduce_func);
store_tile(y_window, cast_tile<YDataType>(y_compute));
}
/// @brief Validates if the given arguments are supported by the 2D reduction kernel.
///
/// @param y_continous_dim Size of the continuous dimension of the output tensor.
/// Must be a multiple of ThreadTile_N for proper thread mapping.
///
/// @param input_strides The stride configuration of the input tensor.
/// The last stride must be 1 to ensure contiguous memory access
/// and enable efficient vectorized loads.
///
/// @return true if the arguments are supported, false otherwise.
/// Error messages are logged when CK_TILE_LOGGING is enabled.
///
/// @note Requirements:
/// - y_continous_dim % ThreadTile_N == 0 (for proper thread distribution)
/// - input_strides[-1] == 1 (for contiguous memory access)
template <typename InputStrides>
CK_TILE_HOST static bool IsSupportedArgument(index_t y_continous_dim,
InputStrides input_strides)
{
using S = typename Problem::BlockShape;
if(y_continous_dim % S::ThreadTile_N != 0)
{
if(ck_tile::EnvIsEnabled(CK_TILE_ENV(CK_TILE_LOGGING)))
{
CK_TILE_ERROR("Total reduction size should be a multiple of ThreadTile_N!");
}
return false;
}
if(input_strides.at(number<input_strides.size() - 1>{}) != 1)
{
if(ck_tile::EnvIsEnabled(CK_TILE_ENV(CK_TILE_LOGGING)))
{
CK_TILE_ERROR(
"Input tensor's last stride must be 1 to support correct vector access!");
}
return false;
}
return true;
}
};
} // namespace ck_tile