docs: public static DMatrixRMaj rref(DMatrixRMaj A , int numUnknowns, DMatrixRMaj reduced ) {
          if( reduced == null ) {
              reduced = new DMatrixRMaj(A.numRows,A.numCols);
          }
          reduced.reshape(A.numRows,A.numCols);
  
          if( numUnknowns <= 0 )
              numUnknowns = Math.min(A.numCols,A.numRows);
  
          ReducedRowEchelonForm_F64<DMatrixRMaj> alg = new RrefGaussJordanRowPivot_DDRM();
          alg.setTolerance(elementMaxAbs(A)* UtilEjml.EPS*Math.max(A.numRows,A.numCols));
  
          reduced.set(A);
          alg.reduce(reduced, numUnknowns);
  
          return reduced;
      }