pto.trowargmin

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

Summary

Get the column index of the minimum element for each row.

Mechanism

Get the column index of the minimum element for each row.

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

\[ \mathrm{dst}_{i,0} = \underset{0 \le j < C}{\operatorname{argmin}} \; \mathrm{src}_{i,j} \]

Syntax

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

Synchronous form:

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

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

IR Level 1 (SSA)

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

IR Level 2 (DPS)

pto.trowargmin 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 TROWARGMIN(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 column index of the row-wise minimum: for each row i, dst[i,0] = argmin of 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 be TileType::Vec.

  • Supported source element types: half, float.

  • Supported destination element types: uint32_t, int32_t.

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

  • dst and src must satisfy the shared row-reduce-index check path used by TRowArgMin.

  • Temporary tile is not used when srcValidCol <= ElementPerRepeat, used when srcValidCol > ElementPerRepeat.

  • tmp tile's rows is the same as src.

  • Simply set tmp tile size the same as src when src is small.

  • tmp tile's stride can be calculated out based on src's validCol using the following formula:

repeats = ceil(validCol / elementPerRepeat)
stride = ceil(repeats * 2 / elementPerBlock) * elementPerBlock + ceil(repeats / elementPerBlock) * elementPerBlock

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
  • Runtime checks follow the shared row-reduce check path:
  • src.GetValidRow() != 0
  • src.GetValidCol() != 0
  • src.GetValidRow() == dst.GetValidRow()

A2A3 implementation checks

  • dst is checked through the shared row-reduce-index path and may use either of these non-fractal layouts:
  • DN layout with one column (BLayout::ColMajor, Cols == 1), or
  • ND layout whose valid column count is 1.

A5 implementation checks

  • In the checked A5 implementation path, tmp is accepted by the interface but not used by TROWARGMIN_IMPL.

About temporary tile tmp for A3

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, uint32_t, 16, 1, BLayout::ColMajor>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TROWARGMIN(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, uint32_t, 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);
  TROWARGMIN(dst, src, tmp);
}

Auto Mode

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

PTO Assembly Form

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