llvm/mlir/include/mlir/ExecutionEngine/SparseTensor/COO.h

//===- COO.h - Coordinate-scheme sparse tensor representation ---*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains a coordinate-scheme representation of sparse tensors.
//
//===----------------------------------------------------------------------===//

#ifndef MLIR_EXECUTIONENGINE_SPARSETENSOR_COO_H
#define MLIR_EXECUTIONENGINE_SPARSETENSOR_COO_H

#include <algorithm>
#include <cassert>
#include <cinttypes>
#include <functional>
#include <vector>

namespace mlir {
namespace sparse_tensor {

/// An element of a sparse tensor in coordinate-scheme representation
/// (i.e., a pair of coordinates and value). For example, a rank-1
/// vector element would look like
///   ({i}, a[i])
/// and a rank-5 tensor element would look like
///   ({i,j,k,l,m}, a[i,j,k,l,m])
///
/// The coordinates are represented as a (non-owning) pointer into a
/// shared pool of coordinates, rather than being stored directly in this
/// object. This significantly improves performance because it reduces the
/// per-element memory footprint and centralizes the memory management for
/// coordinates. The only downside is that the coordinates themselves cannot
/// be retrieved without knowing the rank of the tensor to which this element
/// belongs (and that rank is not stored in this object).
template <typename V>
struct Element final { … };

/// Closure object for `operator<` on `Element` with a given rank.
template <typename V>
struct ElementLT final { … };

/// A memory-resident sparse tensor in coordinate-scheme representation
/// (a collection of `Element`s). This data structure is used as an
/// intermediate representation, e.g., for reading sparse tensors from
/// external formats into memory.
template <typename V>
class SparseTensorCOO final { … };

} // namespace sparse_tensor
} // namespace mlir

#endif // MLIR_EXECUTIONENGINE_SPARSETENSOR_COO_H