code: public static double elementMaxAbs( DMatrix4 a ) {
          double max = Math.abs(a.a1);
          double tmp = Math.abs(a.a2); if( tmp > max ) max = tmp;
          tmp = Math.abs(a.a2); if( tmp > max ) max = tmp;
          tmp = Math.abs(a.a3); if( tmp > max ) max = tmp;
          tmp = Math.abs(a.a4); if( tmp > max ) max = tmp;
  
          return max;
      }
docs: <p>
  Returns the absolute value of the element in the vector that has the largest absolute value.<br>
  <br>
  Max{ |a<sub>i</sub>| } for all i<br>
  </p>
  
  @param a A matrix. Not modified.
  @return The max abs element value of the vector.