[ITK] [ITK-users] Is this a bug ?

[Cyril Mory]

Hello, ITK users,

I've encountered a behavior with vnl_matrix, and I'm wondering whether 
it is a bug or a feature. The following code outputs differents results:

#include <iostream>
#include <vnl_vector.h>
#include <vnl_matrix.h>

int main()
{
   vnl_matrix<double> matrix(2, 2);
   matrix.put(0, 0, 4);
   matrix.put(0, 1, 3);
   matrix.put(1, 0, 2);
   matrix.put(1, 1, 1);

   // Display the matrix
   std::cout << "Matrix" << std::endl;
   std::cout << matrix << std::endl;

   // Display the first row of the matrix,
   vnl_vector<double> matrixRow;
   matrixRow = matrix.get_row(0);
   std::cout << "First row, stored in a vnl_vector" << std::endl;
   std::cout << matrixRow << std::endl;

   double* matrixRowData = matrix.get_row(0).data_block();
   std::cout << "First row, stored in a double*" << std::endl;
   std::cout << matrixRowData[0] << " " << matrixRowData[1] << std::endl;

   double* matrixRowDataFromVector = matrixRow.data_block();
   std::cout << "First row, stored in a double* after passing through a 
vnl_vector" << std::endl;
   std::cout << matrixRowDataFromVector[0] << " " << 
matrixRowDataFromVector[1] << std::endl;

   return EXIT_SUCCESS;
}

Output :

Matrix

4 3

2 1

First row, stored in a vnl_vector

4 3

First row, stored in a double*

0 3

First row, stored in a double* after passing through a vnl_vector

4 3



It was compiled with the following CMakeLists.txt:


cmake_minimum_required(VERSION 2.8)

project(IsThisAvnlBug)

find_package(ITK REQUIRED)
include(${ITK_USE_FILE})

add_executable(IsThisAvnlBug MACOSX_BUNDLE IsThisAvnlBug.cxx)
target_link_libraries(IsThisAvnlBug ${ITK_LIBRARIES})

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