Re: [eigen] Vectorwise dot product feature request

[Johan Pauwels <johan.pauwels@xxxxxxxxxxxxx>]

On 2010-07-07 13:02, Aron Ahmadia wrote:

That looks suspiciously like a transposed multiply to me...

Ugh, exactly. Sorry for the bother. My mind was so set on a collection of independent columns and broadcasting operations, that I forgot the basic matrix multiplication. One might wonder why there even is a ..dot() syntax?

Regards,
Johan

A

On Wed, Jul 7, 2010 at 1:59 PM, Johan Pauwels <johan.pauwels@xxxxxxxxxxxxx> wrote:

Hello all,

Would it be possible to allow a vectorwise dot product as in the example below?

#include <Eigen/Core>

int main()
{
   Eigen::MatrixXf mat = Eigen::MatrixXf::Random(5,2);
   Eigen::VectorXf vec = Eigen::VectorXf::Random(5);
   Eigen::RowVectorXf result(2);

   // this syntax
   result = mat.colwise().dot(vec);
   // instead of this for loop
   for (int i = 0; i < mat.cols(); ++i)
   {
       result[i] = mat.col(i).dot(vec);
   }
}

Regards,
Johan