code: public static void multAdd(DMatrix1Row a , DMatrix1Row b , DMatrix1Row c )
      {
          if( b.numCols == 1 ) {
              MatrixVectorMult_DDRM.multAdd(a, b, c);
          } else {
              if( b.numCols >= EjmlParameters.MULT_COLUMN_SWITCH ) {
                  MatrixMatrixMult_DDRM.multAdd_reorder(a,b,c);
              } else {
                  MatrixMatrixMult_DDRM.multAdd_small(a,b,c);
              }
          }
      }
docs: <p>
  Performs the following operation:<br>
  <br>
  c = c + a * b<br>
  c<sub>ij</sub> = c<sub>ij</sub> + &sum;<sub>k=1:n</sub> { a<sub>ik</sub> * b<sub>kj</sub>}
  </p>
  
  @param a The left matrix in the multiplication operation. Not modified.
  @param b The right matrix in the multiplication operation. Not modified.
  @param c Where the results of the operation are stored. Modified.