More details at http://trac.sagemath.org/ticket/15443



On Thursday, November 21, 2013 9:20:46 AM UTC-5, Volker Braun wrote:
>
> I did some testing and 
>
> 1) ecm uses different seeds all the time, for example 
>
> echo 179424673 | /home/vbraun/Code/sage/local/bin/ecm -I 1 -c 1000000000 
> -cofdec -one 8.0
>
> produces a different output every time.
>
> 2) Occasionally, ecm.py does a lot more factorizations and then eventually 
> times out. Using strace, I see that, for example, the following is run when 
> it eventually times out;
>
> echo 251951573867253012259144010843 | /home/vbraun/Code/sage/local/bin/ecm 
> -I 1 -c 1000000000 -cofdec -one 8.0
>
> Note that the command is rather slow (requires hundreds of trial steps) 
> and that this prime (251951573867253012259144010843) is usually not used as 
> an ecm input. So occasionally (but unlikely) one of the previous 
> computations must yield this number as candidate and then factoring it 
> takes a really long time.
>
>
>
>
> On Thursday, November 21, 2013 12:25:36 AM UTC-5, Volker Braun wrote:
>
>> Another random test failure that I get is from ecm, for example on eno or 
>> mark:
>>
>> sage -t --long src/sage/interfaces/ecm.py
>>     Timed out
>> **********************************************************************
>> Tests run before process (pid=8764) timed out:
>> sage: f = ECM() ## line 169 ##
>> sage: n = 508021860739623467191080372196682785441177798407961 ## line 170 
>> ##
>> sage: f.one_curve(n, B1=10000, sigma=11) ## line 171 ##
>> [1, 508021860739623467191080372196682785441177798407961]
>> sage: f.one_curve(n, B1=10000, sigma=1022170541) ## line 173 ##
>> [79792266297612017, 6366805760909027985741435139224233]
>> sage: n = 432132887883903108009802143314445113500016816977037257 ## line 
>> 175 ##
>> sage: f.one_curve(n, B1=500000, algorithm="P-1") ## line 176 ##
>> [67872792749091946529, 6366805760909027985741435139224233]
>> sage: n = 2088352670731726262548647919416588631875815083 ## line 178 ##
>> sage: f.one_curve(n, B1=2000, algorithm="P+1", x0=5) ## line 179 ##
>> [328006342451, 6366805760909027985741435139224233]
>> sage: sig_on_count() ## line 181 ##
>> 0
>> sage: f = ECM() ## line 241 ##
>> sage: n = 508021860739623467191080372196682785441177798407961 ## line 242 
>> ##
>> sage: f.find_factor(n) ## line 243 ##
>> [79792266297612017, 6366805760909027985741435139224233]
>> sage: f=2^2^14+1 ## line 247 ##
>> sage: ecm.find_factor(f) ## line 248 ##
>> sage: sig_on_count() ## line 252 ##
>> 0
>> sage: ecm.factor(602400691612422154516282778947806249229526581) ## line 
>> 333 ##
>> [45949729863572179, 13109994191499930367061460439]
>> sage: ecm.factor((2^197 + 1)/3)           # takes a long time ## line 336 
>> ##
>>
>> **********************************************************************
>>
>> Has anybody seen this before or an idea what it is about? Random seed 
>> integers that are sometimes bad, perhaps?
>>
>> And yes, this is with SAGE_TIMEOUT_LONG=5000 on mark.
>>
>

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