[eigen] Possible bug in vector-matrix multiplication?

[Manoj Rajagopalan <rmanoj@xxxxxxxxx>]

Hi eigen developers,

   The following test program and output performs w=v*M; where w and v are Nx1 
column vectors and M is NxN matrix. This statement, IMHO, should result in a 
compile-time error since the product isn't defined. Instead, the effect seems 
to be w = M.col(0) \kron v  where \kron denotes tensor product: w is resized 
to be (N^2)x1 column vector.

  This brings me to another question: is there some way to disable automatic 
right-side resizing during an assignment? This would help to trap bugs such 
as the above. The automatic resizing is not always desirable.

Thanks,
Manoj 

----------- Sample program and result --------------


#include <Eigen/Core>
#include <iostream>

using namespace Eigen;
using namespace std;

int main(void)
{
        typedef Matrix<double,Dynamic,1> dvector;
        typedef Matrix<double,Dynamic,Dynamic> dge_matrix;
        int const N = 5;
        dvector v(N);
        for(int i=0;i<N;++i) v[i] = double(i+1);
        dge_matrix M(N,N);
        for(int j=0; j<N; ++j)
                for(int i=0; i<N; ++i)
                        M(i,j) = double(10*(i+1)+(j+1));
        dvector w(N);
        w = v*M;
        cout << "v' = " << v.transpose() << endl;
        cout << "M =\n" << M << endl;
        cout << "w' = " << w.transpose() << endl;
        return 0;
}



v' = 1 2 3 4 5
M =
11 12 13 14 15
21 22 23 24 25
31 32 33 34 35
41 42 43 44 45
51 52 53 54 55
w' =  11  22  33  44  55  21  42  63  84 105  31  62  93 124 155  41  82 123 
164 205  51 102 153 204 255