MatrixBase::diagonalView issue 604

libeigen/eigen!2126

Closes #604

Eigen/src/Core/DiagonalMatrix.h

@@ -372,6 +372,53 @@ bool MatrixBase<Derived>::isDiagonal(const RealScalar& prec) const {
   return true;
 }
 
+/** \returns DiagonalWrapper.
+ *
+ * Example: \include MatrixBase_diagonalView.cpp
+ * Output: \verbinclude MatrixBase_diagonalView.out
+ *
+ * \sa diagonalView()
+ */
+
+/** This is the non-const version of diagonalView() with DiagIndex_ . */
+template <typename Derived>
+template <int DiagIndex_>
+EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<Derived, DiagIndex_>> MatrixBase<Derived>::diagonalView() {
+  typedef Diagonal<Derived, DiagIndex_> DiagType;
+  typedef DiagonalWrapper<DiagType> ReturnType;
+  DiagType diag(this->derived());
+  return ReturnType(diag);
+}
+
+/** This is the const version of diagonalView() with DiagIndex_ . */
+template <typename Derived>
+template <int DiagIndex_>
+EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<const Derived, DiagIndex_>> MatrixBase<Derived>::diagonalView() const {
+  typedef Diagonal<const Derived, DiagIndex_> DiagType;
+  typedef DiagonalWrapper<DiagType> ReturnType;
+  DiagType diag(this->derived());
+  return ReturnType(diag);
+}
+
+/** This is the non-const version of diagonalView() with dynamic index. */
+template <typename Derived>
+EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<Derived, DynamicIndex>> MatrixBase<Derived>::diagonalView(Index index) {
+  typedef Diagonal<Derived, DynamicIndex> DiagType;
+  typedef DiagonalWrapper<DiagType> ReturnType;
+  DiagType diag(this->derived(), index);
+  return ReturnType(diag);
+}
+
+/** This is the const version of diagonalView() with dynamic index. */
+template <typename Derived>
+EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<const Derived, DynamicIndex>> MatrixBase<Derived>::diagonalView(
+    Index index) const {
+  typedef Diagonal<const Derived, DynamicIndex> DiagType;
+  typedef DiagonalWrapper<DiagType> ReturnType;
+  DiagType diag(this->derived(), index);
+  return ReturnType(diag);
+}
+
 namespace internal {
 
 template <>

Eigen/src/Core/MatrixBase.h

@@ -274,6 +274,17 @@ class MatrixBase : public DenseBase<Derived> {
                     const RealScalar& prec = NumTraits<Scalar>::dummy_precision()) const;
   bool isUnitary(const RealScalar& prec = NumTraits<Scalar>::dummy_precision()) const;
 
+  /* diagonalView */
+  template <int DiagIndex_ = 0>
+  EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<Derived, DiagIndex_>> diagonalView();
+
+  template <int DiagIndex_ = 0>
+  EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<const Derived, DiagIndex_>> diagonalView() const;
+
+  EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<Derived, DynamicIndex>> diagonalView(Index index);
+
+  EIGEN_DEVICE_FUNC DiagonalWrapper<Diagonal<const Derived, DynamicIndex>> diagonalView(Index index) const;
+
   /** \returns true if each coefficients of \c *this and \a other are all exactly equal.
    * \warning When using floating point scalar values you probably should rather use a
    *          fuzzy comparison such as isApprox()

doc/snippets/MatrixBase_diagonalView.cpp

@@ -0,0 +1,5 @@
+Matrix3d mat3;
+mat3 << 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7, 8.8, 9.9;
+cout << "Here's the matrix m:" << endl << m << endl;
+cout << "m.diagonal().asDiagonal() returns: " << m.diagonal().asDiagonal() << endl;
+cout << "m.diagonalView() returns: " << m.diagonalView() << endl;

test/CMakeLists.txt

@@ -211,6 +211,7 @@ ei_add_test(product_small)
 ei_add_test(product_large)
 ei_add_test(product_extra)
 ei_add_test(diagonalmatrices)
+ei_add_test(diagonalview)
 ei_add_test(skew_symmetric_matrix3)
 ei_add_test(adjoint)
 ei_add_test(diagonal)

test/diagonalview.cpp

@@ -0,0 +1,55 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// discard stack allocation as that too bypasses malloc
+#define EIGEN_STACK_ALLOCATION_LIMIT 0
+// heap allocation will raise an assert if enabled at runtime
+#define EIGEN_RUNTIME_NO_MALLOC
+
+#include "main.h"
+using namespace std;
+template <typename MatrixType>
+void diagonalview(const MatrixType& m) {
+  enum { Rows = MatrixType::RowsAtCompileTime, Cols = MatrixType::ColsAtCompileTime };
+  Index rows = m.rows();
+  Index cols = m.cols();
+  // create random matrix
+  MatrixType m1 = MatrixType::Random(rows, cols);
+
+  // check equivalence to diagonal(i).asDiagonal() for dynamic indexes
+  VERIFY_IS_APPROX(m1.diagonal(0).asDiagonal().toDenseMatrix(), m1.diagonalView(0).toDenseMatrix());
+  // subdiagonal
+  VERIFY_IS_APPROX(m1.diagonal(-1).asDiagonal().toDenseMatrix(), m1.diagonalView(-1).toDenseMatrix());
+  // superdiagonal
+  VERIFY_IS_APPROX(m1.diagonal(1).asDiagonal().toDenseMatrix(), m1.diagonalView(1).toDenseMatrix());
+
+  // check equivalence to diagonal(i).asDiagonal() for compile time indexes
+  VERIFY_IS_APPROX(m1.diagonal(0).asDiagonal().toDenseMatrix(), m1.template diagonalView<0>().toDenseMatrix());
+  // sub
+  VERIFY_IS_APPROX(m1.diagonal(-1).asDiagonal().toDenseMatrix(), m1.template diagonalView<-1>().toDenseMatrix());
+  // super
+  VERIFY_IS_APPROX(m1.diagonal(1).asDiagonal().toDenseMatrix(), m1.template diagonalView<1>().toDenseMatrix());
+
+  // check const overloads
+  const auto m2(m1);
+  typedef decltype(m1) Type1;
+  typedef decltype(m2) Type2;
+  constexpr bool types_are_same = std::is_same<Type1, Type2>::value;
+  VERIFY(!types_are_same);
+
+  VERIFY_IS_APPROX(m2.diagonal(0).asDiagonal().toDenseMatrix(), m2.diagonalView(0).toDenseMatrix());
+  VERIFY_IS_APPROX(m2.diagonal(1).asDiagonal().toDenseMatrix(), m2.template diagonalView<1>().toDenseMatrix());
+}
+
+EIGEN_DECLARE_TEST(diagonalview) {
+  for (int i = 0; i < g_repeat; i++) {
+    CALL_SUBTEST_1(diagonalview(Matrix<float, 3, 3>()));
+    CALL_SUBTEST_2(diagonalview(Matrix<int, 50, 50>()));
+  }
+}