Added conservativeResize + unit test.

Eigen/src/Core/Matrix.h

@@ -321,6 +321,67 @@ class Matrix
       else resize(other.rows(), other.cols());
     }
 
+    /** Resizes \c *this to a \a rows x \a cols matrix while leaving old values of *this untouched.
+    *
+    * This method is intended for dynamic-size matrices, although it is legal to call it on any
+    * matrix as long as fixed dimensions are left unchanged. If you only want to change the number
+    * of rows and/or of columns, you can use conservativeResize(NoChange_t, int), 
+    * conservativeResize(int, NoChange_t).
+    *
+    * The top-left part of the resized matrix will be the same as the overlapping top-left corner 
+    * of *this. In case values need to be appended to the matrix they will be uninitialized per
+    * default and set to zero when init_with_zero is set to true.
+    */
+    inline void conservativeResize(int rows, int cols, bool init_with_zero = false)
+    {
+      // Note: Here is space for improvement. Basically, for conservativeResize(int,int),
+      // neither RowsAtCompileTime or ColsAtCompileTime must be Dynamic. If only one of the 
+      // dimensions is dynamic, one could use either conservativeResize(int rows, NoChange_t) or
+      // conservativeResize(NoChange_t, int cols). For these methods new static asserts like
+      // EIGEN_STATIC_ASSERT_DYNAMIC_ROWS and EIGEN_STATIC_ASSERT_DYNAMIC_COLS would be good.
+      EIGEN_STATIC_ASSERT_DYNAMIC_SIZE(Matrix)
+      PlainMatrixType tmp = init_with_zero ? PlainMatrixType::Zero(rows, cols) : PlainMatrixType(rows,cols);
+      const int common_rows = std::min(rows, this->rows());
+      const int common_cols = std::min(cols, this->cols());
+      tmp.block(0,0,common_rows,common_cols) = this->block(0,0,common_rows,common_cols);
+      this->derived().swap(tmp);
+    }
+
+    EIGEN_STRONG_INLINE void conservativeResize(int rows, NoChange_t, bool init_with_zero = false)
+    {
+      // Note: see the comment in conservativeResize(int,int,bool)
+      conservativeResize(rows, cols(), init_with_zero);
+    }
+
+    EIGEN_STRONG_INLINE void conservativeResize(NoChange_t, int cols, bool init_with_zero = false)
+    {
+      // Note: see the comment in conservativeResize(int,int,bool)
+      conservativeResize(rows(), cols, init_with_zero);
+    }
+
+    /** Resizes \c *this to a vector of length \a size while retaining old values of *this.
+    *
+    * \only_for_vectors. This method does not work for
+    * partially dynamic matrices when the static dimension is anything other
+    * than 1. For example it will not work with Matrix<double, 2, Dynamic>.
+    *
+    * When values are appended, they will be uninitialized per default and set
+    * to zero when init_with_zero is set to true.
+    */
+    inline void conservativeResize(int size, bool init_with_zero = false)
+    {
+      EIGEN_STATIC_ASSERT_VECTOR_ONLY(Matrix)
+      EIGEN_STATIC_ASSERT_DYNAMIC_SIZE(Matrix)
+
+      if (RowsAtCompileTime == 1 || ColsAtCompileTime == 1)
+      {
+        PlainMatrixType tmp = init_with_zero ? PlainMatrixType::Zero(size) : PlainMatrixType(size);
+        const int common_size = std::min<int>(this->size(),size);
+        tmp.segment(0,common_size) = this->segment(0,common_size);
+        this->derived().swap(tmp);
+      }
+    }
+
     /** Copies the value of the expression \a other into \c *this with automatic resizing.
       *
       * *this might be resized to match the dimensions of \a other. If *this was a null matrix (not already initialized),

Eigen/src/Core/util/StaticAssert.h

@@ -62,6 +62,7 @@
         THIS_METHOD_IS_ONLY_FOR_MATRICES_OF_A_SPECIFIC_SIZE,
         YOU_MADE_A_PROGRAMMING_MISTAKE,
         YOU_CALLED_A_FIXED_SIZE_METHOD_ON_A_DYNAMIC_SIZE_MATRIX_OR_VECTOR,
+        YOU_CALLED_A_DYNAMIC_SIZE_METHOD_ON_A_FIXED_SIZE_MATRIX_OR_VECTOR,
         UNALIGNED_LOAD_AND_STORE_OPERATIONS_UNIMPLEMENTED_ON_ALTIVEC,
         NUMERIC_TYPE_MUST_BE_FLOATING_POINT,
         NUMERIC_TYPE_MUST_BE_REAL,
@@ -114,6 +115,11 @@
   EIGEN_STATIC_ASSERT(TYPE::SizeAtCompileTime!=Eigen::Dynamic, \
                       YOU_CALLED_A_FIXED_SIZE_METHOD_ON_A_DYNAMIC_SIZE_MATRIX_OR_VECTOR)
 
+// static assertion failing if the type \a TYPE is not dynamic-size
+#define EIGEN_STATIC_ASSERT_DYNAMIC_SIZE(TYPE) \
+  EIGEN_STATIC_ASSERT(TYPE::SizeAtCompileTime==Eigen::Dynamic, \
+                      YOU_CALLED_A_DYNAMIC_SIZE_METHOD_ON_A_FIXED_SIZE_MATRIX_OR_VECTOR)
+
 // static assertion failing if the type \a TYPE is not a vector type of the given size
 #define EIGEN_STATIC_ASSERT_VECTOR_SPECIFIC_SIZE(TYPE, SIZE) \
   EIGEN_STATIC_ASSERT(TYPE::IsVectorAtCompileTime && TYPE::SizeAtCompileTime==SIZE, \

test/CMakeLists.txt

@@ -149,6 +149,7 @@ ei_add_test(sparse_solvers " " "${SPARSE_LIBS}")
 ei_add_test(umeyama)
 ei_add_test(householder)
 ei_add_test(swap)
+ei_add_test(conservative_resize)
 
 ei_add_property(EIGEN_TESTING_SUMMARY "CXX:               ${CMAKE_CXX_COMPILER}\n")
 if(CMAKE_COMPILER_IS_GNUCXX)

test/conservative_resize.cpp

@@ -0,0 +1,129 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra. Eigen itself is part of the KDE project.
+//
+// Copyright (C) 2009 Hauke Heibel <hauke.heibel@gmail.com>
+//
+// Eigen is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 3 of the License, or (at your option) any later version.
+//
+// Alternatively, you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or1 FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License or the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License and a copy of the GNU General Public License along with
+// Eigen. If not, see <http://www.gnu.org/licenses/>.
+
+#include "main.h"
+
+#include <Eigen/Core>
+#include <Eigen/Array>
+
+using namespace Eigen;
+
+template <typename Scalar, int Storage>
+void run_matrix_tests()
+{
+  typedef Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic, Storage> MatrixType;
+
+  MatrixType m, n;
+
+  // boundary cases ...
+  m = n = MatrixType::Random(50,50);
+  m.conservativeResize(1,50);
+  VERIFY_IS_APPROX(m, n.block(0,0,1,50));
+
+  m = n = MatrixType::Random(50,50);
+  m.conservativeResize(50,1);
+  VERIFY_IS_APPROX(m, n.block(0,0,50,1));
+
+  m = n = MatrixType::Random(50,50);
+  m.conservativeResize(50,50);
+  VERIFY_IS_APPROX(m, n.block(0,0,50,50));
+
+  // random shrinking ...
+  for (int i=0; i<25; ++i)
+  {
+    const int rows = ei_random<int>(1,50);
+    const int cols = ei_random<int>(1,50);
+    m = n = MatrixType::Random(50,50);
+    m.conservativeResize(rows,cols);
+    VERIFY_IS_APPROX(m, n.block(0,0,rows,cols));
+  }
+
+  // random growing with zeroing ...
+  for (int i=0; i<25; ++i)
+  {
+    const int rows = ei_random<int>(50,75);
+    const int cols = ei_random<int>(50,75);
+    m = n = MatrixType::Random(50,50);
+    m.conservativeResize(rows,cols,true);
+    VERIFY_IS_APPROX(m.block(0,0,n.rows(),n.cols()), n);
+    VERIFY( rows<=50 || m.block(50,0,rows-50,cols).sum() == Scalar(0) );
+    VERIFY( cols<=50 || m.block(0,50,rows,cols-50).sum() == Scalar(0) );
+  }
+}
+
+template <typename Scalar>
+void run_vector_tests()
+{
+  typedef Matrix<Scalar, 1, Eigen::Dynamic> MatrixType;
+
+  MatrixType m, n;
+
+  // boundary cases ...
+  m = n = MatrixType::Random(50);
+  m.conservativeResize(1);
+  VERIFY_IS_APPROX(m, n.segment(0,1));
+
+  m = n = MatrixType::Random(50);
+  m.conservativeResize(50);
+  VERIFY_IS_APPROX(m, n.segment(0,50));
+
+  // random shrinking ...
+  for (int i=0; i<50; ++i)
+  {
+    const int size = ei_random<int>(1,50);
+    m = n = MatrixType::Random(50);
+    m.conservativeResize(size);
+    VERIFY_IS_APPROX(m, n.segment(0,size));
+  }
+
+  // random growing with zeroing ...
+  for (int i=0; i<50; ++i)
+  {
+    const int size = ei_random<int>(50,100);
+    m = n = MatrixType::Random(50);
+    m.conservativeResize(size,true);
+    VERIFY_IS_APPROX(m.segment(0,50), n);
+    VERIFY( size<=50 || m.segment(50,size-50).sum() == Scalar(0) );
+  }
+}
+
+void test_conservative_resize()
+{
+  run_matrix_tests<int, Eigen::RowMajor>();
+  run_matrix_tests<int, Eigen::ColMajor>();
+  run_matrix_tests<float, Eigen::RowMajor>();
+  run_matrix_tests<float, Eigen::ColMajor>();
+  run_matrix_tests<double, Eigen::RowMajor>();
+  run_matrix_tests<double, Eigen::ColMajor>();
+  run_matrix_tests<std::complex<float>, Eigen::RowMajor>();
+  run_matrix_tests<std::complex<float>, Eigen::ColMajor>();
+  run_matrix_tests<std::complex<double>, Eigen::RowMajor>();
+  run_matrix_tests<std::complex<double>, Eigen::ColMajor>();
+
+  run_vector_tests<int>();
+  run_vector_tests<float>();
+  run_vector_tests<double>();
+  run_vector_tests<std::complex<float> >();
+  run_vector_tests<std::complex<double> >();
+}