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Composable Kernel: /home/docs/checkouts/readthedocs.org/user_builds/advanced-micro-devices-composable-kernel/checkouts/develop/include/ck_tile/ops/softmax/block/block_softmax_2d.hpp Source File

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 // SPDX-License-Identifier: MIT
 // Copyright (c) 2018-2023, Advanced Micro Devices, Inc. All rights reserved.
  
 #pragma once
  
 #include "ck_tile/core.hpp"
 #include "ck_tile/ops/reduce.hpp"
  
 #define _BLOCK_SOFTMAX_USE_UNPACK2 0
  
 namespace ck_tile {
  
 /*
 simple 2d softmax implementation, along row (dim=1)
 requirement:
     1). each row is within a warp
     2). data type must be a dword
 */
 template <typename Problem_, typename Policy_ = void>
 struct BlockSoftmax2D
 {
     using Problem = remove_cvref_t<Problem_>;
     using Policy  = remove_cvref_t<Policy_>;
  
     using DataType = typename Problem::DataType;
  
     template <typename DistributedTensor, index_t dim = 1>
     CK_TILE_DEVICE void
     operator()(const DistributedTensor& x, DistributedTensor& y, number<dim> = {})
     {
         const auto f_max = [](auto e0, auto e1) { return max(e0, e1); };
         const auto f_sum = [](auto e0, auto e1) { return e0 + e1; };
 #if _BLOCK_SOFTMAX_USE_UNPACK2
         const auto f_max3 = [](auto e0, auto e1, auto e2) {
             float rtn;
             asm volatile("v_max3_f32 %0, %1, %2, %3" : "=v"(rtn) : "v"(e0), "v"(e1), "v"(e2));
             return rtn;
         };
         const auto f_sum3 = [](auto e0, auto e1, auto e2) { return e0 + e1 + e2; };
 #endif
  
         // compute row max
         auto reduce_row_max = BlockReduce2D{x, -numeric<DataType>::infinity()};
 #if _BLOCK_SOFTMAX_USE_UNPACK2
         auto row_max = reduce_row_max(f_max3, f_max, sequence<1, 2>{});
 #else
         auto row_max = reduce_row_max(f_max);
 #endif
         sweep_tile<DistributedTensor>([&](auto idx) {
             constexpr auto row_id = make_tuple(idx[number<0>{}]);
             y(idx)                = exp(x[idx] - row_max[row_id]);
         });
  
         // compute row sum
         auto reduce_row_sum = BlockReduce2D<decltype(y)>{y, DataType{0}};
 #if _BLOCK_SOFTMAX_USE_UNPACK2
         auto row_sum = reduce_row_sum(f_sum3, f_sum, sequence<1, 2>{});
 #else
         auto row_sum = reduce_row_sum(f_sum);
 #endif
         // reciprocal
         auto r = make_static_distributed_tensor<DataType>(row_sum.get_tile_distribution());
         sweep_tile(row_sum, [&](auto idx) { r(idx) = DataType{1} / row_sum(idx); });
  
         // scale
         sweep_tile<DistributedTensor>([&](auto idx) {
             constexpr auto row_id = make_tuple(idx[number<0>{}]);
             y(idx)                = y(idx) * r(row_id);
         });
     }
  
     template <typename DistributedTensor, index_t dim = 1>
     CK_TILE_DEVICE decltype(auto) operator()(const DistributedTensor& x, number<dim> = {})
     {
         auto y = DistributedTensor{}; // distributed tensor
         operator()(x, y, number<dim>{});
         return y;
     }
 };
  
 } // namespace ck_tile