cutlass/examples/88_hopper_fmha/kernel/fmha_tile_scheduler.hpp

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#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/fast_math.h"
#include "cutlass/kernel_hardware_info.h"

namespace cutlass::fmha::kernel {

////////////////////////////////////////////////////////////////////////////////

struct IndividualTileScheduler {

  struct Params {
    dim3 grid;
  };

  bool valid_ = true;

  CUTLASS_DEVICE
  IndividualTileScheduler(Params const&) {}

  template<class ProblemSize, class ClusterShape, class TileShape>
  static Params to_underlying_arguments(
      ProblemSize const& problem_size, KernelHardwareInfo hw_info,
      ClusterShape const& cluster_shape, TileShape const& tile_shape)
  {
    using namespace cute;
    dim3 grid(round_up(ceil_div(size<2>(problem_size), size<0>(tile_shape)), size<0>(cluster_shape)), size<0>(problem_size), size<1>(problem_size));
    return Params{ grid };
  }

  static dim3 get_grid_shape(Params const& params) {
    return params.grid;
  }

  CUTLASS_DEVICE
  bool is_valid() {
    return valid_;
  }

  CUTLASS_DEVICE
  auto get_block_coord() {
    using namespace cute;
    return make_coord(blockIdx.x, _0{}, make_coord(blockIdx.y, blockIdx.z));
  }

  CUTLASS_DEVICE
  IndividualTileScheduler& operator++() {
    valid_ = false;
    return *this;
  }
};

////////////////////////////////////////////////////////////////////////////////

struct PersistentTileScheduler {

  struct Params {
    int num_blocks;
    FastDivmod divmod_m_block;
    FastDivmod divmod_b;
    FastDivmod divmod_h;

    KernelHardwareInfo hw_info;
  };

  int block_idx = 0;
  Params params;

  CUTLASS_DEVICE
  PersistentTileScheduler(Params const& params) : block_idx(blockIdx.x), params(params) {}

  template<class ProblemSize, class ClusterShape, class TileShape>
  static Params to_underlying_arguments(
      ProblemSize const& problem_size, KernelHardwareInfo hw_info,
      ClusterShape const& cluster_shape, TileShape const& tile_shape)
  {
    using namespace cute;
    // Get SM count if needed, otherwise use user supplied SM count
    int sm_count = hw_info.sm_count;
    if (sm_count <= 0) {
      CUTLASS_TRACE_HOST("  WARNING: Arguments do not include a valid SM count.\n"
          "  For optimal performance, populate the arguments KernelHardwareInfo struct with the SM count.");
      sm_count = KernelHardwareInfo::query_device_multiprocessor_count(hw_info.device_id);
    }

    CUTLASS_TRACE_HOST("to_underlying_arguments(): Setting persistent grid SM count to " << sm_count);
    hw_info.sm_count = sm_count;

    int num_m_blocks = cutlass::round_up(ceil_div(size<2>(problem_size), size<0>(tile_shape)), size<0>(cluster_shape));
    int num_blocks = num_m_blocks * size<0>(problem_size) * size<1>(problem_size);

    return Params {
      num_blocks,
      { num_m_blocks}, { size<0>(problem_size) }, { size<1>(problem_size) },
      hw_info
    };
  }

  static dim3 get_grid_shape(Params const& params) {
    dim3 grid(std::min(params.num_blocks, params.hw_info.sm_count), 1, 1);
    return grid;
  }

  CUTLASS_DEVICE
  bool is_valid() {
    return block_idx < params.num_blocks;
  }

  CUTLASS_DEVICE
  auto get_block_coord() {
    using namespace cute;
    int block_decode = block_idx;
    int m_block, bidb, bidh;
    params.divmod_m_block(block_decode, m_block, block_decode);
    params.divmod_b(block_decode, bidb, block_decode);
    params.divmod_h(block_decode, bidh, block_decode);
    return make_coord(m_block, _0{}, make_coord(bidb, bidh));
  }

  CUTLASS_DEVICE
  PersistentTileScheduler& operator++() {
    block_idx += gridDim.x;
    return *this;
  }
};

////////////////////////////////////////////////////////////////////////////////

template<typename Base>
struct TileSchedulerBwdAdapter {

  using Params = typename Base::Params;

  Base base_;

  CUTLASS_DEVICE
  TileSchedulerBwdAdapter(Params const& params) : base_(params) {}

  template<class ProblemSize, class ClusterShape, class TileShape>
  static Params to_underlying_arguments(
      ProblemSize const& problem_size, KernelHardwareInfo hw_info,
      ClusterShape const& cluster_shape, TileShape const& tile_shape)
  {
    using namespace cute;
    return Base::to_underlying_arguments(select<0,1,3,2,4>(problem_size), hw_info, select<1,0,2>(cluster_shape), select<1,0,2>(tile_shape));
  }

  static dim3 get_grid_shape(Params const& params) {
    return Base::get_grid_shape(params);
  }

  CUTLASS_DEVICE
  bool is_valid() {
    return base_.is_valid();
  }

  CUTLASS_DEVICE
  auto get_block_coord() {
    using namespace cute;
    return select<1,0,2>(base_.get_block_coord());
  }

  CUTLASS_DEVICE
  TileSchedulerBwdAdapter& operator++() {
    ++base_;
    return *this;
  }
};

////////////////////////////////////////////////////////////////////////////////

}  // namespace cutlass::fmha::kernel