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Ublas :

From: Ott Toomet (otoomet_at_[hidden])
Date: 2005-09-13 07:08:08

Dear list,

I would like to write some functions in c++ which will be called from
R. The matrix data will be passed and returned as double* array. The
problem is to force a matrix to share the same memory as double*
array. Examples in a similar thread

seem not to work for me, the array contents will be copied to matrix
at it's initialisation but later changes are not reflected there any
more. E.g.


#include <boost/numeric/ublas/vector.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/io.hpp>

using namespace boost::numeric::ublas;

int main() {
    double a[] = {-11, -12, -13, -14};
   array_adaptor<double> st (4, a);
   vector<double, array_adaptor<double> > v(4, st);
   unsigned i;
   a[1] = 100;
   std::cout << "before initialisation: v " << v << std::endl;
   for(i = 0; i < 4; ++i)
     v(i) = i + 0.1;
   std::cout << "after " << v << std::endl;
   std::cout << a[1] << std::endl;

results in

  siim_at_hugo:~/tyyq/newmat$ ./aakatse
  before initialisation: v [4](-11,-12,-13,-14)
  after [4](0.1,1.1,2.1,3.1)

Note that a[1] (still equal to 100) is not overwritten by v(1).

Do I miss something?

The compilation was performed by

g++ -c aakatse.c++ -O2 -Wall -Wno-unknown-pragmas -I/usr/include
g++ aakatse.o -O2 -Wall -Wno-unknown-pragmas -L/usr/lib -lm -o aakatse

I have

g++ (GCC) 3.4.3 20050227 (Red Hat 3.4.3-22.1)