TROWMAX

Instruction Diagram

Introduction

Reduces each row by taking the maximum value across columns.

Mathematical Semantics

Assume R = src.GetValidRow() and C = src.GetValidCol(). For 0 <= i < R:

$$\mathrm{dst}_{i,0} = \max_{0 \le j < C} \mathrm{src}_{i,j}$$

Assembly Syntax

Synchronous form:

%dst = trowmax %src : !pto.tile<...> -> !pto.tile<...>

Reduction may introduce an internal temporary tile; the C++ built-in API requires an explicit tmp operand.

AS Level 1 (SSA)

%dst = pto.trowmax %src, %tmp : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>

AS Level 2 (DPS)

pto.trowmax ins(%src, %tmp : !pto.tile_buf<...>, !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)

C++ Built-in APIs

Declared in include/pto/common/pto_instr.hpp:

The public include header is <pto/pto-inst.hpp>, and the internal declaration is located in pto/common/pto_instr.hpp.

template <typename TileDataOut, typename TileDataIn, typename TileDataTmp, typename... WaitEvents>
PTO_INST RecordEvent TROWMAX(TileDataOut &dst, TileDataIn &src, TileDataTmp &tmp, WaitEvents &... events);

Constraints

General Constraints or Checks

• dst and src must both be TileType::Vec.
• src must use the standard ND layout: row-major and non-fractal (BLayout::RowMajor, SLayout::NoneBox).
• dst must use one of the following two non-fractal layouts:
  • ND layout (BLayout::RowMajor, SLayout::NoneBox), or
  • DN layout with the number of columns strictly equal to 1 (BLayout::ColMajor, SLayout::NoneBox, Cols == 1).
• dst and src must have the same element type.
• Runtime valid region checks:
  • src.GetValidRow() != 0
  • src.GetValidCol() != 0
  • src.GetValidRow() == dst.GetValidRow()
• The built-in API signature requires explicitly passing the tmp operand.

Implementation Check for Atlas A2/A3 Training Products/Atlas A2/A3 Inference Products

• Supported element types (Atlas A2/A3 training products/Atlas A2/A3 inference products): half, float, int32_t, int16_t.
• Supported element types (Ascend 950PR/Ascend 950DT): half, float, int32_t, int16_t, int8_t, uint8_t.
• The implementation accepts both ND output and DN output with Cols == 1.
• Runtime checks follow the shared row reduction check path:
  • src.GetValidRow() != 0
  • src.GetValidCol() != 0
  • src.GetValidRow() == dst.GetValidRow()

Temporary Space

Atlas A2/A3 Training Products/Atlas A2/A3 Inference Products

tmp is used as the scratch storage for row maximum value reduction.

• For integer types (int32_t, int16_t): tmp is used as a per-row accumulator buffer (1 block). For each row, tmp is initialized to the minimum representable value, and then the blocks of src are accumulated through vmax. The final maximum value is read from tmp in scalar mode.
  • tmp size: at least 1 row and BLOCK_BYTE_SIZE / sizeof(T) columns (8 for int32_t, 16 for int16_t).
• For floating-point types (float, half): tmp is used for binary tree reduction through vcmax/vcgmax.
  • Safe default settings: set tmp to the same shape as src.

Ascend 950PR/Ascend 950DT

tmp is accepted by the API but not used by the Ascend 950PR/Ascend 950DT implementation. The Ascend 950PR/Ascend 950DT backend uses vector-register-based reduction (the vcmax instruction) and does not require temporary tile storage. tmp is retained in the C++ built-in API signature only for API compatibility with Atlas A2/A3 training products/Atlas A2/A3 inference products.

Examples

Automatic

#include <pto/pto-inst.hpp>

using namespace pto;

void example_auto() {
  using SrcT = Tile<TileType::Vec, float, 16, 16>;
  using DstT = Tile<TileType::Vec, float, 16, 1, BLayout::ColMajor>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TROWMAX(dst, src, tmp);
}

Manual

#include <pto/pto-inst.hpp>

using namespace pto;

void example_manual() {
  using SrcT = Tile<TileType::Vec, float, 16, 16>;
  using DstT = Tile<TileType::Vec, float, 16, 1, BLayout::ColMajor>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TASSIGN(src, 0x1000);
  TASSIGN(dst, 0x2000);
  TASSIGN(tmp, 0x3000);
  TROWMAX(dst, src, tmp);
}

ASM Examples

Automatic Mode

# Automatic mode: the compiler/runtime is responsible for resource placement and scheduling.
%dst = pto.trowmax %src, %tmp : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>

Manual Mode

# Manual mode: explicitly bind resources first, then issue the instruction.
# Optional (when the instruction contains tile operands):
# pto.tassign %arg0, @tile(0x1000)
# pto.tassign %arg1, @tile(0x2000)
%dst = pto.trowmax %src, %tmp : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>

PTO Assembly Form

%dst = trowmax %src : !pto.tile<...> -> !pto.tile<...>
# AS Level 2 (DPS)
pto.trowmax ins(%src, %tmp : !pto.tile_buf<...>, !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)