test/source/blender/simulation/intern/eigen_utils.h

/* SPDX-FileCopyrightText: Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

#pragma once

/** \file
 * \ingroup sim
 */

#if defined(__GNUC__) && !defined(__clang__)
#  pragma GCC diagnostic push
/* XXX suppress verbose warnings in eigen */
#  pragma GCC diagnostic ignored "-Wlogical-op"
#endif

#include <Eigen/Sparse>
#include <Eigen/src/Core/util/DisableStupidWarnings.h>

#ifdef __GNUC__
#  pragma GCC diagnostic pop
#endif

#include "implicit.h"

using Scalar = float;

/* slightly extended Eigen vector class
 * with conversion to/from plain C float array
 */
class Vector3 : public Eigen::Vector3f {
 public:
  using ctype = float *;

  Vector3() = default;

  Vector3(const ctype &v)
  {
    for (int k = 0; k < 3; k++) {
      coeffRef(k) = v[k];
    }
  }

  Vector3 &operator=(const ctype &v)
  {
    for (int k = 0; k < 3; k++) {
      coeffRef(k) = v[k];
    }
    return *this;
  }

  operator ctype()
  {
    return data();
  }
};

/* slightly extended Eigen matrix class
 * with conversion to/from plain C float array
 */
class Matrix3 : public Eigen::Matrix3f {
 public:
  using ctype = float (*)[3];

  Matrix3() = default;

  Matrix3(const ctype &v)
  {
    for (int k = 0; k < 3; k++) {
      for (int l = 0; l < 3; l++) {
        coeffRef(l, k) = v[k][l];
      }
    }
  }

  Matrix3 &operator=(const ctype &v)
  {
    for (int k = 0; k < 3; k++) {
      for (int l = 0; l < 3; l++) {
        coeffRef(l, k) = v[k][l];
      }
    }
    return *this;
  }

  operator ctype()
  {
    return (ctype)data();
  }
};

using lVector = Eigen::VectorXf;

/* Extension of dense Eigen vectors,
 * providing 3-float block access for blenlib math functions
 */
class lVector3f : public Eigen::VectorXf {
 public:
  using base_t = Eigen::VectorXf;

  lVector3f() = default;

  template<typename T> lVector3f &operator=(T rhs)
  {
    base_t::operator=(rhs);
    return *this;
  }

  float *v3(int vertex)
  {
    return &coeffRef(3 * vertex);
  }

  const float *v3(int vertex) const
  {
    return &coeffRef(3 * vertex);
  }
};

using Triplet = Eigen::Triplet<Scalar>;
using TripletList = std::vector<Triplet>;

using lMatrix = Eigen::SparseMatrix<Scalar>;

/* Constructor type that provides more convenient handling of Eigen triplets
 * for efficient construction of sparse 3x3 block matrices.
 * This should be used for building lMatrix instead of writing to such lMatrix directly (which is
 * very inefficient). After all elements have been defined using the set() method, the actual
 * matrix can be filled using construct().
 */
struct lMatrix3fCtor {
  lMatrix3fCtor() = default;

  void reset()
  {
    m_trips.clear();
  }

  void reserve(int numverts)
  {
    /* reserve for diagonal entries */
    m_trips.reserve(numverts * 9);
  }

  void add(int i, int j, const Matrix3 &m)
  {
    i *= 3;
    j *= 3;
    for (int k = 0; k < 3; k++) {
      for (int l = 0; l < 3; l++) {
        m_trips.emplace_back(i + k, j + l, m.coeff(l, k));
      }
    }
  }

  void sub(int i, int j, const Matrix3 &m)
  {
    i *= 3;
    j *= 3;
    for (int k = 0; k < 3; k++) {
      for (int l = 0; l < 3; l++) {
        m_trips.emplace_back(i + k, j + l, -m.coeff(l, k));
      }
    }
  }

  void construct(lMatrix &m)
  {
    m.setFromTriplets(m_trips.begin(), m_trips.end());
    m_trips.clear();
  }

 private:
  TripletList m_trips;
};

using ConjugateGradient =
    Eigen::ConjugateGradient<lMatrix, Eigen::Lower, Eigen::DiagonalPreconditioner<Scalar>>;

using Eigen::ComputationInfo;

BLI_INLINE void print_lvector(const lVector3f &v)
{
  for (int i = 0; i < v.rows(); i++) {
    if (i > 0 && i % 3 == 0) {
      printf("\n");
    }

    printf("%f,\n", v[i]);
  }
}

BLI_INLINE void print_lmatrix(const lMatrix &m)
{
  for (int j = 0; j < m.rows(); j++) {
    if (j > 0 && j % 3 == 0) {
      printf("\n");
    }

    for (int i = 0; i < m.cols(); i++) {
      if (i > 0 && i % 3 == 0) {
        printf("  ");
      }

      implicit_print_matrix_elem(m.coeff(j, i));
    }
    printf("\n");
  }
}