On Sun, Jan 29, 2023 at 3:04 PM G. M.-S. <lists....@gmail.com> wrote:
>
>
> For me, with SageMath version 9.8.beta7
>
> sage: ecm.factor(71281426948143699070565)
>
> does not return quickly either.
>
> Indeed, running
>
> sage: ecm.interact()
>
> seems to show a strange behaviour for 71281426948143699070565 when factoring
> the factors found.
> As this is probabilistic and the output changes every time, I do not copy it
> here.
Basically, the default B1 value is too large in this case.
sage: ecm.factor(71281426948143699070565,B1=200) # almost instant
[5, 53, 337, 1873, 2833, 7507, 20037791]
sage: ecm.factor(71281426948143699070565,B1=2000) # takes looong time
the docs say:
* "B1" -- initial lower bound, defaults to 2000 (15 digit factors).
Used if "factor_digits" is not specified.
>
> Guillermo
>
> On Sun, 29 Jan 2023 at 15:41, Bill Witzke <bwitzk...@gmail.com> wrote:
>>
>> Hi,
>>
>> I have a hard time factoring the number 71281426948143699070565 using
>> ecm.factor(). No result is given after a few minutes runtime. Though,
>> plain factor() happily factors the number. Factoring smaller or larger
>> numbers work fine with ecm.factor(), too. Just the single given number
>> seems to be problematic.
>>
>> Am I doing something wrong? Can someone confirm?
>>
>> system:
>> Ubuntu 22.04
>> sagemath 9.5-4 (via apt)
>> Intel Pentium N5000
>> (SageMath and Python beginner)
>>
>> example code factoring numbers in the range [71281426948143699070565 - L,
>> 71281426948143699070565 + L]:
>>
>> # Odd number.
>> n = 71281426948143699070565
>> # Limit.
>> L = 2
>> # Iterate over interval [-L, L].
>> for i in range(-L, L + 1):
>> m = n + i
>> print("%d => %s" % (m, ecm.factor(m)))
>
>
>
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