They should all be equivalent. The choice of defining polynomial for the 
Hecke eigenvalue field is possibly different in each run since computing 
the dual eigenvalues uses a random algorithm. A workaround could be to set 
a random seed in the beginning using 
set_random_seed(0)

.


On Saturday, August 31, 2019 at 3:38:12 AM UTC-7, John Cremona wrote:
>
>
> ---------- Forwarded message ---------
> From: Ethan Yang <[email protected] <javascript:>>
> Date: Sat, 31 Aug 2019, 06:44
> Subject: [sage-devel] Newforms calculation is nondeterministic
> To: sage-devel <[email protected] <javascript:>>
>
>
> Calculating newforms of a cuspidal subspace gives different answers on 
> different runs. 
>
> I did not (and don't know how to) check whether the newforms are 
> equivalent (and if they aren't, this would be a much more serious bug), 
> but, regardless, this type of calculation should definitely be 
> deterministic.
>
> *Steps to reproduce:*
>
> eps = kronecker_character(105)
>
> M2 = ModularForms(eps)
>
> S2 = M2.cuspidal_subspace()
>
> print(S2.newforms('a'))
>
>
> Running it multiple times, one gets a variety of q-expansions for the 
> newforms. Here I have listed 4 that I have received in output.
>
>
> [q + (-1/10*a0^3 + 3/10*a0^2 + 2/5*a0 - 3/5)*q^2 + (-1/10*a0^3 + 3/10*a0^2 
> - 3/5*a0 - 3/5)*q^3 + q^4 + (a0 - 1)*q^5 + O(q^6),
>
>  q - 1/2*a1*q^3 - 2*q^4 + (-1/24*a1^3 - 1/3*a1)*q^5 + O(q^6),
>
>  q + (-1/10*a2^3 + 3/10*a2^2 + 2/5*a2 - 3/5)*q^2 + (1/10*a2^3 - 3/10*a2^2 
> + 3/5*a2 + 3/5)*q^3 + q^4 + (-a2 + 1)*q^5 + O(q^6)]
>
>
> [q + (-1/22*a0^3 - 3/11*a0^2 - 1/2*a0 - 3/11)*q^2 + (1/44*a0^3 + 3/22*a0^2 
> + 3/4*a0 + 3/22)*q^3 + q^4 + (-3/44*a0^3 - 9/22*a0^2 - 5/4*a0 - 31/22)*q^5 
> + O(q^6), 
>
> q - 1/2*a1*q^3 - 2*q^4 + (-1/24*a1^3 - 1/3*a1)*q^5 + O(q^6), 
>
> q + (-1/22*a2^3 - 3/11*a2^2 - 1/2*a2 - 3/11)*q^2 + (-1/44*a2^3 - 3/22*a2^2 
> - 3/4*a2 - 3/22)*q^3 + q^4 + (3/44*a2^3 + 9/22*a2^2 + 5/4*a2 + 31/22)*q^5 + 
> O(q^6)]
>
>
> [q + (-1/10*a0^3 - 3/10*a0^2 + 2/5*a0 + 3/5)*q^2 + (1/10*a0^3 + 3/10*a0^2 
> + 3/5*a0 - 3/5)*q^3 + q^4 + (-1/5*a0^3 - 3/5*a0^2 - 1/5*a0 + 1/5)*q^5 + 
> O(q^6), 
>
> q - 1/2*a1*q^3 - 2*q^4 + (-1/24*a1^3 - 1/3*a1)*q^5 + O(q^6), 
>
> q + (-1/22*a2^3 - 3/11*a2^2 - 1/2*a2 - 3/11)*q^2 + (-1/44*a2^3 - 3/22*a2^2 
> - 3/4*a2 - 3/22)*q^3 + q^4 + (3/44*a2^3 + 9/22*a2^2 + 5/4*a2 + 31/22)*q^5 + 
> O(q^6)]
>
>
> [q + (-1/22*a0^3 + 3/11*a0^2 - 1/2*a0 + 3/11)*q^2 + (-1/44*a0^3 + 
> 3/22*a0^2 - 3/4*a0 + 3/22)*q^3 + q^4 + (-1/44*a0^3 + 3/22*a0^2 + 1/4*a0 - 
> 19/22)*q^5 + O(q^6), 
>
> q - a1*q^3 - 2*q^4 + (-1/3*a1^3 - 2/3*a1)*q^5 + O(q^6), 
>
> q + (-1/10*a2^3 - 3/10*a2^2 + 2/5*a2 + 3/5)*q^2 + (-1/10*a2^3 - 3/10*a2^2 
> - 3/5*a2 + 3/5)*q^3 + q^4 + (1/5*a2^3 + 3/5*a2^2 + 1/5*a2 - 1/5)*q^5 + 
> O(q^6)]
>
>
> Version: 8.7
> OS: macOS High Sierra 10.13.6, 64 Bit
>
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