New Post: How to apply operation over vector from each row/column of a matrix?

 for (int majorItem = 0; majorItem < t.Length; majorItem++)
 {
     for (int i = 0; i < items; i++)
          t[majorItem] += mt[ptr + i * minorStride];

     ptr += majorStride;
 }

For every k in M
     mv = M.GetColumnVector(k);
     mv += v ;