pto.trowmax

pto.trowmax is part of the Reduce And Expand instruction set.

Summary

Reduce each row by taking the maximum across columns.

Mechanism

Reduce each row by taking the maximum across columns.

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

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

Syntax

Textual spelling is defined by the PTO ISA syntax-and-operands pages.

Synchronous form:

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

Lowering may introduce internal scratch tiles; the C++ intrinsic 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++ Intrinsic

Declared in include/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);

Inputs

  • src is the source tile.
  • tmp is a temporary tile used for intermediate storage.
  • dst names the destination tile. The operation iterates over dst's valid region.

Expected Outputs

dst holds the row-wise maximum: for each row i, dst[i,0] = max of all elements in row i of src.

Side Effects

No architectural side effects beyond producing the destination tile. Does not implicitly fence unrelated traffic.

Constraints

Constraints

General constraints / checks

  • dst and src must both be TileType::Vec.

  • src must use standard ND layout: row-major and non-fractal (BLayout::RowMajor, SLayout::NoneBox).

  • dst must use one of the following non-fractal layouts:

  • ND layout (BLayout::RowMajor, SLayout::NoneBox), or

  • DN layout with exactly one column (BLayout::ColMajor, SLayout::NoneBox, Cols == 1).

  • dst and src must use the same element type.

  • Runtime valid-region checks:

  • src.GetValidRow() != 0
  • src.GetValidCol() != 0

  • src.GetValidRow() == dst.GetValidRow()

  • Supported element types: half, float, int32_t, int16_t.

  • The implementation accepts both ND output and DN output with Cols == 1.

  • Runtime checks follow the shared row-reduce check path:

  • src.GetValidRow() != 0
  • src.GetValidCol() != 0

  • src.GetValidRow() == dst.GetValidRow()

  • The current implementation path passes tmp into the backend call, but this document does not add extra tmp shape/layout constraints beyond what is explicitly enforced by the checked implementation.

Exceptions

Exceptions

  • Illegal operand tuples, unsupported types, invalid layout combinations, or unsupported target-profile modes are rejected by the verifier or by the selected backend instruction set.
  • Programs must not rely on behavior outside the documented legal domain of this operation, even if one backend currently accepts it.

Target-Profile Restrictions

Target-Profile Restrictions
  • The intrinsic signature requires an explicit tmp operand.

A2A3 implementation checks

Examples

Auto

#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);
}

Auto Mode

# Auto mode: compiler/runtime-managed placement and scheduling.
%dst = pto.trowmax %src, %tmp : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>

Manual Mode

# Manual mode: bind resources explicitly before issuing the instruction.
# Optional for 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<...>)