docs: private IntIntPair nonZeroPivotSearch(int k) {
  
      int i, j;
      double absValue;
      for(i = k; i < coeff.length; i++) {
        for(j = k; j < coeff[0].length; j++) {
          // compute absolute value of
          // current entry in absValue
          absValue = Math.abs(coeff[row[i]][col[j]]);
  
          // check if absValue is non-zero
          if(absValue > 0) { // found a pivot element
            return new IntIntPair(i, j);
          } // end if
        } // end for j
      } // end for k
      return new IntIntPair(k, k);
    }