pto.tcolsum

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

Summary

Reduce each column by summing across rows.

Mechanism

Reduce each column by summing across rows.

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

\[ \mathrm{dst}_{0,j} = \sum_{i=0}^{R-1} \mathrm{src}_{i,j} \]

isBinary selects the implementation path (binary-tree accumulation vs. sequential accumulation).

Syntax

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

Synchronous form:

%dst = tcolsum %src {isBinary = false} : !pto.tile<...> -> !pto.tile<...>

Lowering may introduce internal scratch tiles; the C++ intrinsic requires an explicit tmp operand.

AS Level 1 (SSA)

%dst = pto.tcolsum %src : !pto.tile<...> -> !pto.tile<...>
%dst = pto.tcolsum %src, %tmp {isBinary = false} : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>

AS Level 2 (DPS)

pto.tcolsum ins(%src : !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)
pto.tcolsum ins(%src, %tmp {isBinary = false} : !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... WaitEvents>
PTO_INST RecordEvent TCOLSUM(TileDataOut &dst, TileDataIn &src, WaitEvents &... events);

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

Inputs

  • src is the source tile.
  • dst names the destination tile. The operation iterates over dst's valid region.
  • isBinary (bool): selects the implementation path—binary-tree accumulation (true) or sequential accumulation (false).

Expected Outputs

dst holds the column-wise sum: for each column j, dst[0,j] = sum of all elements in column j 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 be TileType::Vec.

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

  • dst and src must use the same element type.

  • Runtime checks:

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

  • src.GetValidCol() <= tmp row stride measured in src elements

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

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

  • tmp must use the same element type as src and dst.

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
  • isBinary selects the checked backend path:
  • true: binary-tree accumulation using tmp
  • false: sequential accumulation into dst
  • If src.GetValidRow() == 0 or src.GetValidCol() == 0, the implementation returns early.

  • Shared A5 column-reduce checks allow half, float, int8_t, uint8_t, int16_t, uint16_t, int32_t, uint32_t, bfloat16_t.

  • The checked A5 TCOLSUM path still takes tmp only for the binary accumulation path; no extra compile-time tmp type/layout assertions are explicitly enforced in TCOLSUM_IMPL.

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, 1, 16>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TCOLSUM(dst, src, tmp, /*isBinary=*/false);
}

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, 1, 16>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TASSIGN(src, 0x1000);
  TASSIGN(dst, 0x2000);
  TASSIGN(tmp, 0x3000);
  TCOLSUM(dst, src, tmp, /*isBinary=*/false);
}

Auto Mode

# Auto mode: compiler/runtime-managed placement and scheduling.
%dst = pto.tcolsum %src : !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.tcolsum %src : !pto.tile<...> -> !pto.tile<...>

PTO Assembly Form

%dst = tcolsum %src {isBinary = false} : !pto.tile<...> -> !pto.tile<...>
# AS Level 2 (DPS)
pto.tcolsum ins(%src : !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)