The period() method for BinaryRecurrenceSequence not functioning when the period mod m is non-simple

asked 0 years ago

D O'D
3 ●2

updated 0 years ago

Max Alekseyev

6982 ●9 ●52 ●164

BinaryRecurrenceSequence is not throwing an error when there is not a simple period.

For instance, the sequence given by S = BinaryRecurrenceSequence(3,2,u0=0,u1=1) considered mod 4 has terms when considered individually: 0, 1, 3, 3, 3, ..... It does (eventually) have a period, it's just not a simple one.

When, however I try S.period(4), sagemath just stops working without throwing an error and I have to kill the kernel. Is there a method to test whether there are non-simple periods, or which otherwise picks up on sequences like this?

Often I run scripts over multiple sequences with different values for the coefficients, so it's not a case of being able to test each sequence in turn whether there will be an issue.

add a comment

def myperiod(S,mod): T = dict() k = 0 while True: t = (S(k)%mod,S(k+1)%mod) if t in T: return k-T[t] T[t] = k k += 1 print( myperiod( BinaryRecurrenceSequence(3,2,u0=0,u1=1), 4 ) )

Comments

Thank you - that's helpful! And also for reporting it as a bug :)

D O'D ( 0 years ago )

add a comment

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

The period() method for BinaryRecurrenceSequence not functioning when the period mod m is non-simple

1 Answer

Comments

Your Answer

Question Tools

Stats

The period() method for BinaryRecurrenceSequence not functioning when the period mod m is non-simple savecancel

1 Answer

Comments

Your Answer

Question Tools

Stats

The period() method for BinaryRecurrenceSequence not functioning when the period mod m is non-simple