code: public static LinearSolverDense<DMatrixRMaj> leastSquares(int numRows , int numCols ) {
          if(numCols < EjmlParameters.SWITCH_BLOCK64_QR )  {
              return new LinearSolverQrHouseCol_DDRM();
          } else {
              if( EjmlParameters.MEMORY == EjmlParameters.MemoryUsage.FASTER )
                  return new LinearSolverQrBlock64_DDRM();
              else
                  return new LinearSolverQrHouseCol_DDRM();
          }
      }
docs: Creates a good general purpose solver for over determined systems and returns the optimal least-squares
  solution.  The A matrix will have dimensions (m,n) where m &ge; n.
  
  @param numRows The number of rows that the decomposition is optimized for.
  @param numCols The number of columns that the decomposition is optimized for.
  @return A new least-squares solver for over determined systems.