threadblock_swizzle.h

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/*! \file
    \brief Implements several possible threadblock-swizzling functions mapping blockIdx to 
      GEMM problems.
*/

#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/layout/matrix.h"
#include "cutlass/platform/platform.h"
#include "cutlass/gemm/gemm.h"
#include "cutlass/conv/conv2d_problem_size.h"
#include "cutlass/conv/conv3d_problem_size.h"
#include "cutlass/gemm/threadblock/index_remat.h"
#include "cutlass/gemm/threadblock/threadblock_swizzle_streamk.h"

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

namespace cutlass {
namespace gemm {
namespace threadblock {

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

/// Threadblock swizzling function for GEMMs
template <int N = 1>
struct GemmIdentityThreadblockSwizzle {

  CUTLASS_HOST_DEVICE
  GemmIdentityThreadblockSwizzle() { }

  /// Returns the shape of the problem in units of logical tiles
  /// *Gemm* problem size: gemm(M, N, K)
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    GemmCoord problem_size,
    GemmCoord tile_size,
    int split_k_slices) {

    return GemmCoord(
      (problem_size.m() + tile_size.m() - 1) / tile_size.m(),
      (problem_size.n() + tile_size.n() - 1) / tile_size.n(),
      split_k_slices);
  }

  /// Returns the shape of the problem in units of logical tiles
  /// *ImplicitGemm* Conv2d problem size: conv_operator(NPQK, NHWC, KRSC)
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    cutlass::conv::Operator conv_operator,
    cutlass::conv::Conv2dProblemSize const &problem_size,
    GemmCoord tile_size,
    int split_k_slices) {

    gemm::GemmCoord implicit_gemm_problem_size = 
    cutlass::conv::implicit_gemm_problem_size(conv_operator, problem_size);

    return get_tiled_shape(
      implicit_gemm_problem_size, tile_size, split_k_slices);
  }

  /// Returns the shape of the problem in units of logical tiles
  /// *ImplicitGemm* Conv3d problem size: conv_operator(NZPQK, NDHWC, KTRSC)
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    cutlass::conv::Operator conv_operator,
    cutlass::conv::Conv3dProblemSize const &problem_size,
    GemmCoord tile_size,
    int split_k_slices) {

    gemm::GemmCoord implicit_gemm_problem_size = 
    cutlass::conv::implicit_gemm_problem_size(conv_operator, problem_size);

    return get_tiled_shape(
      implicit_gemm_problem_size, tile_size, split_k_slices);
  }

  /// Computes CUDA grid dimensions given a size in units of logical tiles
  CUTLASS_HOST_DEVICE
  static dim3 get_grid_shape(GemmCoord tiled_shape) {
    int tile = 1 << get_log_tile(tiled_shape);
    return dim3(tiled_shape.m() * tile, (tiled_shape.n() + tile - 1) / tile, tiled_shape.k());
  }

  /// Calculates optimal swizzle width
  CUTLASS_HOST_DEVICE
  static int get_log_tile(GemmCoord tiled_shape) {
    auto n = tiled_shape.n();
    // Thresholds picked so that it doesn't cause too many no-op CTAs
    if (N >= 8 && n >= 6)
      return 3;
    else if (N >= 4 && n >= 3)
      return 2;
    else if (N >= 2 && n >= 2)
      return 1;
    else
      return 0;
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(int log_tile) {
    int block_idx_x = RematerializeBlockIdxX();
    int block_idx_y = RematerializeBlockIdxY();
    int block_idx_z = RematerializeBlockIdxZ();

    return GemmCoord{(block_idx_x >> log_tile),  //
                     (block_idx_y << log_tile) + ((block_idx_x) & ((1 << (log_tile)) - 1)),
                     block_idx_z};
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(GemmCoord tiled_shape) {

    int const kTile = N;
    int block_idx_x = RematerializeBlockIdxX();
    int block_idx_y = RematerializeBlockIdxY();

    if ((tiled_shape.m() < kTile) || (tiled_shape.n() < kTile))
      return GemmCoord{block_idx_x, block_idx_y, RematerializeBlockIdxZ()};

    return GemmCoord{
      (block_idx_x / kTile),
      (block_idx_y * kTile) + (block_idx_x % kTile),
      RematerializeBlockIdxZ()
    };
  }
};

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

/// Threadblock swizzling function for GEMMs
struct GemmHorizontalThreadblockSwizzle {

  CUTLASS_HOST_DEVICE
  GemmHorizontalThreadblockSwizzle() { }

  /// Returns the shape of the problem in units of logical tiles
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    GemmCoord problem_size,
    GemmCoord tile_size,
    int split_k_slices) {

    return GemmCoord(
      (problem_size.m() + tile_size.m() - 1) / tile_size.m(),
      (problem_size.n() + tile_size.n() - 1) / tile_size.n(),
      split_k_slices);
  }

  /// Computes CUDA grid dimensions given a size in units of logical tiles
  CUTLASS_HOST_DEVICE
  static dim3 get_grid_shape(GemmCoord tiled_shape) {
    return dim3(tiled_shape.n(), tiled_shape.m(), tiled_shape.k());
  }

  /// Calculates optimal swizzle width
  CUTLASS_HOST_DEVICE
  static int get_log_tile(GemmCoord tiled_shape) {
    return 0;
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(GemmCoord tiled_shape) {
    return GemmCoord{
      RematerializeBlockIdxY(),
      RematerializeBlockIdxX(),
      RematerializeBlockIdxZ()
    };
  }
};

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

/// Threadblock swizzling function for batched GEMMs
struct GemmBatchedIdentityThreadblockSwizzle {

  /// Returns the shape of the problem in units of logical tiles
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    GemmCoord problem_size,
    GemmCoord tile_size,
    int batch_count) {

    return GemmCoord(
      (problem_size.m() + tile_size.m() - 1) / tile_size.m(),
      (problem_size.n() + tile_size.n() - 1) / tile_size.n(),
      batch_count % (1 << 16));
  }

  /// Computes CUDA grid dimensions given a size in units of logical tiles
  CUTLASS_HOST_DEVICE
  static dim3 get_grid_shape(GemmCoord tiled_shape) {
    return dim3(tiled_shape.m(), tiled_shape.n(), tiled_shape.k());
  }

  /// Calculates optimal swizzle width
  CUTLASS_HOST_DEVICE
  static int get_log_tile(GemmCoord tiled_shape) {
    return 0;
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(GemmCoord tiled_shape) {
    return GemmCoord{
      RematerializeBlockIdxX(),
      RematerializeBlockIdxY(),
      RematerializeBlockIdxZ()
    };
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(int log_tile) {
    int block_idx_x = RematerializeBlockIdxX();
    int block_idx_y = RematerializeBlockIdxY();
    int block_idx_z = RematerializeBlockIdxZ();

    return GemmCoord{(block_idx_x >> log_tile),  //
                     (block_idx_y << log_tile) + ((block_idx_x) & ((1 << (log_tile)) - 1)),
                     block_idx_z};
  }

  /// Gets the batch index
  CUTLASS_DEVICE
  static int get_batch_idx() {
    return RematerializeBlockIdxZ();
  }
};

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

/// Threadblock swizzling function for split-K GEMMs
template <int N = 1>
struct GemmSplitKIdentityThreadblockSwizzle {

  int const kTile = N;

  /// Returns the shape of the problem in units of logical tiles
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    GemmCoord problem_size,
    GemmCoord tile_size,
    int partitions) {

    return GemmCoord(
      (problem_size.m() + tile_size.m() - 1) / tile_size.m(),
      (problem_size.n() + tile_size.n() - 1) / tile_size.n(),
      partitions);
  }

  /// Calculates optimal swizzle width
  CUTLASS_HOST_DEVICE
  static int get_log_tile(GemmCoord tiled_shape) {
    auto n = tiled_shape.n();
    // Thresholds picked so that it doesn't cause too many no-op CTAs
    if (N >= 8 && n >= 6)
      return 3;
    else if (N >= 4 && n >= 3)
      return 2;
    else if (N >= 2 && n >= 2)
      return 1;
    else
      return 0;
  }

  /// Computes CUDA grid dimensions given a size in units of logical tiles
  CUTLASS_HOST_DEVICE
  static dim3 get_grid_shape(GemmCoord tiled_shape) {
    int tile = 1 << get_log_tile(tiled_shape);
    return dim3(tiled_shape.m() * tile, (tiled_shape.n() + tile - 1) / tile, tiled_shape.k());
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(int log_tile) {
    int block_idx_x = RematerializeBlockIdxX();
    int block_idx_y = RematerializeBlockIdxY();
    int block_idx_z = RematerializeBlockIdxZ();

    return GemmCoord{(block_idx_x >> log_tile),  //
                     (block_idx_y << log_tile) + ((block_idx_x) & ((1 << (log_tile)) - 1)),
                     block_idx_z};
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(GemmCoord tiled_shape) {

    int const kTile = N;
    int block_idx_x = RematerializeBlockIdxX();
    int block_idx_y = RematerializeBlockIdxY();

    if ((tiled_shape.m() < kTile) || (tiled_shape.n() < kTile))
      return GemmCoord{block_idx_x, block_idx_y, RematerializeBlockIdxZ()};

    return GemmCoord{
      (block_idx_x / kTile),
      (block_idx_y * kTile) + (block_idx_x % kTile),
      RematerializeBlockIdxZ()
    };
  }
};

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

/// Threadblock swizzling function for split-K GEMMs
struct GemmSplitKHorizontalThreadblockSwizzle {

  /// Returns the shape of the problem in units of logical tiles
  CUTLASS_HOST_DEVICE
  static GemmCoord get_tiled_shape(
    GemmCoord problem_size,
    GemmCoord tile_size,
    int partitions) {

    return GemmCoord(
      (problem_size.m() + tile_size.m() - 1) / tile_size.m(),
      (problem_size.n() + tile_size.n() - 1) / tile_size.n(),
      partitions);
  }

  /// Computes CUDA grid dimensions given a size in units of logical tiles
  CUTLASS_HOST_DEVICE
  static dim3 get_grid_shape(GemmCoord tiled_shape) {
    return dim3(tiled_shape.n(), tiled_shape.m(), tiled_shape.k());
  }

  /// Calculates optimal swizzle width
  CUTLASS_HOST_DEVICE
  static int get_log_tile(GemmCoord tiled_shape) {
    return 0;
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(int log_tile) {
    return GemmCoord{
      RematerializeBlockIdxY(),
      RematerializeBlockIdxX(),
      RematerializeBlockIdxZ()
    };
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static GemmCoord get_tile_offset(GemmCoord tiled_shape) {
    return GemmCoord{
      RematerializeBlockIdxY(),
      RematerializeBlockIdxX(),
      RematerializeBlockIdxZ()
    };
  }
};

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

/// Threadblock swizzling function for batched GEMVs
struct GemvBatchedStridedThreadblockDefaultSwizzle {

  /// Returns the shape of the problem in units of logical tiles
  CUTLASS_HOST_DEVICE
  static BatchedGemmCoord get_tiled_shape(
    BatchedGemmCoord problem_size,
    BatchedGemmCoord tile_size) {

    return BatchedGemmCoord(
      1, // M is always 1
      (problem_size.n() + tile_size.n() - 1) / tile_size.n(),
      (problem_size.k() + tile_size.k() - 1) / tile_size.k(),
      (problem_size.batch() + tile_size.batch() - 1) / tile_size.batch());
  }

  /// Computes CUDA grid dimensions given a size in units of logical tiles
  CUTLASS_HOST_DEVICE
  static dim3 get_grid_shape(BatchedGemmCoord tiled_shape) {
    return dim3(tiled_shape.n(), tiled_shape.batch(), tiled_shape.k());
  }

  /// Calculates optimal swizzle width
  CUTLASS_HOST_DEVICE
  static int get_log_tile(GemmCoord tiled_shape) {
    return 0;
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static BatchedGemmCoord get_tile_offset(int log_tile) {
    return BatchedGemmCoord{
      0, // M is always 1
      RematerializeBlockIdxX(),
      RematerializeBlockIdxZ(),
      RematerializeBlockIdxY(),
    };
  }

  /// Obtains the threadblock offset (in units of threadblock-scoped tiles)
  CUTLASS_DEVICE
  static BatchedGemmCoord get_tile_offset() {
    return BatchedGemmCoord{
      0, // M is always 1
      RematerializeBlockIdxX(),
      RematerializeBlockIdxZ(),
      RematerializeBlockIdxY(),
    };
  }

  /// Gets the batch tile index
  CUTLASS_DEVICE
  static int get_batch_tile_idx() {
    return RematerializeBlockIdxY();
  }

  /// Gets the absolute batch index
  CUTLASS_DEVICE
  static int get_batch_idx() {
    return RematerializeBlockDimY()*RematerializeBlockIdxY() + RematerializeThreadIdxY();
  }
};

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

} // namespace threadblock
} // namespace gemm
} // namespace cutlass