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Old 2005-08-14, 20:57   #1
rpropper
 
Dec 2004

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Default probably a stupid newbie question...

Hi all,

Sorry if this is a stupid newbie question, but I was trying to use ECM to factor a number and didn't get any results. The program ran, reported how long it took to complete step 1 and step 2, and terminated. Here was the input/output:

---

> echo "23648598680196674293592660374220409521936469024442760646483443630416927852665392144342050729272084591548384873564046388884876395326286172771630075104410787261" | ./ecm 11e7
GMP-ECM 6.0.1 [powered by GMP 4.1.2] [ECM]
Input number is 23648598680196674293592660374220409521936469024442760646483443630416927852665392144342050729272084591548384873564046388884876395326286172771630075104410787261 (158 digits)
Using B1=110000000, B2=680270182898, polynomial Dickson(30), sigma=4069758861
Step 1 took 4143830ms
Step 2 took 1127850ms

---

Does anyone know of parameters I need to use to actually get a factor for this integer? (I know it's not prime -- I already checked that with Primo).

Thanks for your help!
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Old 2005-08-14, 22:24   #2
cjohnsto
 
Jun 2005

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But you did get a result: 1 curve at B1=11e7 found no factors.

To run multiple curves youneed to tell it to do so. I think the parameter is -c # where # is the number of curves to run.

I also suggest you pipe the output to a file so you don't lose it if the computer crashes.

echo "236...261" | ./ecm -c 100 11e7 >> out.txt &; tail -f out.txt

This way you still see the output and have it saved.
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Old 2005-08-15, 03:00   #3
rpropper
 
Dec 2004

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I see now. Thanks for the clarification. I had erroneously assumed that ECM would continue trying curves until it found a factorization. My mistake...thanks again :)
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Old 2005-08-15, 07:57   #4
cjohnsto
 
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No problem.
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Old 2005-08-15, 09:06   #5
xilman
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Quote:
Originally Posted by rpropper
Hi all,

Sorry if this is a stupid newbie question, but I was trying to use ECM to factor a number and didn't get any results. The program ran, reported how long it took to complete step 1 and step 2, and terminated. Here was the input/output:

---

> echo "236485986..." | ./ecm 11e7
GMP-ECM 6.0.1 [powered by GMP 4.1.2] [ECM]
Input number is 236485986... (158 digits)
sigma=4069758861
As a matter of interest, what is that number?


Paul
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Old 2005-10-12, 15:00   #6
VJS
 
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You can keep it running until it finds a factor by adding the following in your command line.

-one -c 10000

so something like this

ecm -one -c 10000 B1 B2 <number.txt >results.txt

Bascially the -one will allow the program to run until a factor is found overriding the -c switch.

-c 10000 the number of curves to run until it stops in this case 10000 curves

>results.txt dumps all of the screen output to a file, careful this file is overwritten each time you restart the client.
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Old 2005-10-12, 19:38   #7
smh
 
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Quote:
Originally Posted by VJS
ecm -one -c 10000 B1 B2 <number.txt >results.txt

>results.txt dumps all of the screen output to a file, careful this file is overwritten each time you restart the client.
If you put this in a batch file you'd better put >> results.txt so the results will be appended. You'll need to manually clean up the file ones in a while though.

<numbers.txt can be replaced with -inp numbers.txt

And if you add -nn it will run at idle priority
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Old 2005-10-12, 20:05   #8
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> vs >> Oh my god!!! Lets leave it at that.

Is there a command to output the results to both the screen and a file??? Since I didn't know the >> I thought I'd ask.

-----------------

You can also do -save file.txt and -resume file.txt for seperating stage1 and 2 if you wish.

Perhaps, I should also ask is there a way to get prime95 to do stage1 of numbers from a file. And I mean decimal expansions not just k,n, from a worktodo.ini .
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Old 2005-10-12, 23:01   #9
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On UNIX you can use tee to do that.

See man tee!
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Old 2005-10-13, 08:22   #10
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Quote:
Originally Posted by garo
On UNIX you can use tee to do that.

See man tee!
On Windows you can get tee in several ways. My preferred route is to install SFU (Services for Unix) which is a free, albeit lengthy, download from microsoft.com

SFU gives you a large collection of Unix-like tools and a Unix-like environment all well integrated in your normal Windows environment. In particular, you get the gcc compiler and everything else necessary to build your own binary of ecm, optimized for your own cpu.

Other alternatives exist, Cygwin for instance, but I really believe that SFU is far superior.
I don't run a Windows box without SFU installed.

Paul
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Old 2005-10-13, 10:27   #11
ET_
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Quote:
Originally Posted by xilman
On Windows you can get tee in several ways. My preferred route is to install SFU (Services for Unix) which is a free, albeit lengthy, download from microsoft.com

SFU gives you a large collection of Unix-like tools and a Unix-like environment all well integrated in your normal Windows environment. In particular, you get the gcc compiler and everything else necessary to build your own binary of ecm, optimized for your own cpu.

Other alternatives exist, Cygwin for instance, but I really believe that SFU is far superior.
I don't run a Windows box without SFU installed.

Paul

Do you mean that with SFU one could compile with GMP without the hassle of cygwin libraries? :surprised

Luigi
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