eigen_utils.h

// Copyright 2004-present Facebook. All Rights Reserved.

#ifndef CAFFE2_OPERATORS_UTILS_EIGEN_H_
#define CAFFE2_OPERATORS_UTILS_EIGEN_H_

#include "Eigen/Core"
#include "Eigen/Dense"
#include "caffe2/core/logging.h"

namespace caffe2 {

// 1-d array
template <typename T>
using EArrXt = Eigen::Array<T, Eigen::Dynamic, 1>;
using EArrXf = Eigen::ArrayXf;
using EArrXd = Eigen::ArrayXd;
using EArrXi = Eigen::ArrayXi;
using EArrXb = EArrXt<bool>;

// 2-d array, column major
template <typename T>
using EArrXXt = Eigen::Array<T, Eigen::Dynamic, Eigen::Dynamic>;
using EArrXXf = Eigen::ArrayXXf;

// 2-d array, row major
template <typename T>
using ERArrXXt =
    Eigen::Array<T, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
using ERArrXXf = ERArrXXt<float>;

// 1-d vector
template <typename T>
using EVecXt = Eigen::Matrix<T, Eigen::Dynamic, 1>;
using EVecXd = Eigen::VectorXd;
using EVecXf = Eigen::VectorXf;

// 1-d row vector
using ERVecXd = Eigen::RowVectorXd;
using ERVecXf = Eigen::RowVectorXf;

// 2-d matrix, column major
template <typename T>
using EMatXt = Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>;
using EMatXd = Eigen::MatrixXd;
using EMatXf = Eigen::MatrixXf;

// 2-d matrix, row major
template <typename T>
using ERMatXt =
    Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
using ERMatXd = ERMatXt<double>;
using ERMatXf = ERMatXt<float>;

namespace utils {

template <typename T>
Eigen::Map<const EArrXt<T>> AsEArrXt(const std::vector<T>& arr) {
  return {arr.data(), static_cast<int>(arr.size())};
}
template <typename T>
Eigen::Map<EArrXt<T>> AsEArrXt(std::vector<T>& arr) {
  return {arr.data(), static_cast<int>(arr.size())};
}

// return a sub array of 'array' based on indices 'indices'
template <class Derived, class Derived1, class Derived2>
void GetSubArray(
    const Eigen::ArrayBase<Derived>& array,
    const Eigen::ArrayBase<Derived1>& indices,
    Eigen::ArrayBase<Derived2>* out_array) {
  CAFFE_ENFORCE_EQ(array.cols(), 1);
  // using T = typename Derived::Scalar;

  out_array->derived().resize(indices.size());
  for (int i = 0; i < indices.size(); i++) {
    DCHECK_LT(indices[i], array.size());
    (*out_array)[i] = array[indices[i]];
  }
}

// return a sub array of 'array' based on indices 'indices'
template <class Derived, class Derived1>
EArrXt<typename Derived::Scalar> GetSubArray(
    const Eigen::ArrayBase<Derived>& array,
    const Eigen::ArrayBase<Derived1>& indices) {
  using T = typename Derived::Scalar;
  EArrXt<T> ret(indices.size());
  GetSubArray(array, indices, &ret);
  return ret;
}

// return a sub array of 'array' based on indices 'indices'
template <class Derived>
EArrXt<typename Derived::Scalar> GetSubArray(
    const Eigen::ArrayBase<Derived>& array,
    const std::vector<int>& indices) {
  return GetSubArray(array, AsEArrXt(indices));
}

// return 2d sub array of 'array' based on row indices 'row_indices'
template <class Derived, class Derived1, class Derived2>
void GetSubArrayRows(
    const Eigen::ArrayBase<Derived>& array2d,
    const Eigen::ArrayBase<Derived1>& row_indices,
    Eigen::ArrayBase<Derived2>* out_array) {
  out_array->derived().resize(row_indices.size(), array2d.cols());

  for (int i = 0; i < row_indices.size(); i++) {
    DCHECK_LT(row_indices[i], array2d.size());
    out_array->row(i) =
        array2d.row(row_indices[i]).template cast<typename Derived2::Scalar>();
  }
}

// return indices of 1d array for elements evaluated to true
template <class Derived>
std::vector<int> GetArrayIndices(const Eigen::ArrayBase<Derived>& array) {
  std::vector<int> ret;
  for (int i = 0; i < array.size(); i++) {
    if (array[i]) {
      ret.push_back(i);
    }
  }
  return ret;
}

} // namespace utils
} // namespace caffe2

#endif