Many number field functions involve calculations over real/complex fields. Sometimes it may be necessary to increase the precision used internally. On the other hand, since the default precision is quite high, some calculations may be sped up by decreasing it -- at the user's own risk!
Note however that many functions will work automatically with a much larger precision if necessary to guarantee P digits for the user. Generally all functions take care of the necessary precision. Only under rare circumstances will any computation fail because of precision loss.
Set the precision to be used internally for real/complex calculations involving the field F or the order O to be n.The second integer m sets the precision for some unit calculations (this may become obsolete).