Re: Precision too low in bnfisprincipal

[Aurel Page <aurel.page@normalesup.org>]

    Hi Gareth,
    
    You have to use flag=2 or flag=4 in bnfisprincipal, see
    ?bnfisprincipal.
    
    ? \p 20000
    ? bnf = bnfinit(x^2+199,1);
    ? bnfisprincipal(bnf, bnf.gen[1]^9)
      *** bnfisprincipal: Warning: precision too low for generators, not
    given.
    % = [[1]~, []~]
    ? bnfisprincipal(bnf, bnf.gen[1]^9, 2)
    % = [1]~
    ? bnfisprincipal(bnf, bnf.gen[1]^9, 4)
    % = [[1]~, matrix(0,2)]
    
    Best,
    Aurel

On 21/12/2023 08:02, Gareth Ma wrote:

Sorry, I accidentally hit sent. Here is the code and output again:

? \p 20000     
? bnf = bnfinit(x^2 + 199, flag=1);
? bnfisprincipal(bnf, bnf.gen[1] ^ 9)
  *** bnfisprincipal: Warning: precision too low for generators, not given.
%10 = [[1]~, []~]

I can reproduce this on the browser version too. I am not sure what is happening or how to fix it. Should I raise the precision even higher? Is this intended?

Best regards,

Gareth

On 21/12/2023 06:58, Gareth Ma wrote:

Hi all. I am trying to use `bnfisprincipal`, but it is somehow failing even for very small inputs. Here is an example:

default(realprecision, 2000);

bnf = bnfinit(x^2 + 199, flag=1)bnfisprincipal(bnf, bnf.gen[1] ^ 9)
  *** bnfisprincipal: Warning: precision too low for generators, not given.
%7 = [[1]~, []~]