On Dec 16, 2008, at 07:17 , William Stein wrote:

>
> On Tue, Dec 16, 2008 at 12:50 AM, achrzesz <achrz...@wp.pl> wrote:
>>
>> Hallo,
>> I'm wondering what goes  wrong with tis:
>>
>> (sage 3.2 compiled from sources, ubuntu 8.04, quad core 2.4 GHz)
>>
>>
>> sage: for k in range(14,21):
>> ....:     f=2^2^k+1;w=ecm.find_factor(f);[w[0],prod(w)==f]
>> ....:
>> [2, False]
>> [523923, False]
>> [1901173, False]
>> [2, False]
>> [2, False]
>> [30539, False]
>> [2, False]
>>
>> Are the exponents to big?
>>
>> Andrzej Chrzeszczyk
>
> Yes, I think there must be a hard limit on the input line for GMP-ECM.
>   If I try the first number directly on the command line, it says
> "Factor found in step 1: 2".  However the first number is *odd*, so 2
> can't be a factor!
> What's really happening is that GMP-ECM is ignoring everything after
> the first 4095 digits when I paste the input in.

I think you are running into a system limit, not an ECM limit.  Even  
emacs seems to have a problem when I paste in "2^2^14+1".

I finally got this to work by doing

f = open("/tmp/foo", "w")
print >> f, 2^2^14+1
f.close()

in Sage, and then

ecm < /tmp/foo

in the shell:

$ ecm 10000000 100000 < /tmp/foo
GMP-ECM 6.1.3 [powered by GMP 4.2.1] [ECM]
Input number has 4933 digits
Using B1=10000000, B2=100000, polynomial x^1, sigma=3668583302
...

It's likely that the "expect" interface is running into the same  
limit, since it uses the tty sub-system.

All those "bings" are a signal from the system (tty driver) that it's  
choking, and isn't reading what you are throwing at it.

HTH

Justin

--
Justin C. Walker, Curmudgeon-At-Large
Institute for the Absorption of Federal Funds
--------
If you're not confused,
You're not paying attention
--------




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