Eigen boolean matrix plus

Question

I would like to do the boolean matrix plus. How could I do it in Eigen? My following example only gives a scalar +.

#include "Eigen/Dense"
#include <iostream>

using namespace std;
using namespace Eigen;


int main()
{
   Eigen::Matrix<bool, 4, 4> m;
   m << 0,1,1,1,
    1,0,1,0,
    1,1,0,0,
    1,1,1,0;
   cout << m + m;  //should be logical_and here
}

How could I use the logical_and here?

score 1 · Accepted Answer · edited May 23 '17 at 12:24

1

Eigen does not seem to provide specific functions to work on boolean matrices. However you can use the fact that booleans are converted to 0 (false) and 1 (true) reliably (see bool to int conversion). Noting that 0=0*0=0*1=1*0 and 1*1=1 it is obvious that multiplication of the booleans as integers is the same (up to type) as logical and. Therefore the following should work:

#include "Eigen/Dense"
#include <iostream>

using namespace std;
using namespace Eigen;


int main()
{
   Eigen::Matrix<bool, 4, 4> m;
   m << 0,1,1,1,
    1,0,1,0,
    1,1,0,0,
    1,1,1,0;
   Eigen::Matrix<bool, 4, 4> result = m.cwiseProduct(m);
   cout << result;
}

edited May 23 '17 at 12:24

Community

1
1

answered Feb 10 '17 at 02:18

Jonathan von Schroeder

1,683
11
14

Maybe one more question, how to do the boolean matrix multiplication? – wei wang Feb 10 '17 at 05:23
What do you mean by multiplication. The logical AND is the 'multiplication' in the Boolean Algebra. Are you asking about the logical OR? – Jonathan von Schroeder Feb 10 '17 at 05:26
I mean the standard matrix multiplication over two boolean matrices. The + is OR and * is AND. – wei wang Feb 10 '17 at 05:28
Then you seem to have a weird definition of + and * that is pretty non-standard. - Anyways I'll think about how to do OR when I have some time. – Jonathan von Schroeder Feb 10 '17 at 05:31
`(m+m).unaryExpr([](const int x) { return min(1,x); })` using e.g. `min` from `` should do what you want because `1+1=2>1`, `1=0+1=1+0` and `0+0=0<1`. – Jonathan von Schroeder Feb 10 '17 at 05:45

Eigen boolean matrix plus

1 Answers1