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Message boards : Sieving : Sierpinski Problem - Factors Found

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travismac

Joined: 15 Feb 15
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Message 83803 - Posted: 7 Mar 2015 | 3:33:27 UTC

I'm running the Sierpinski Problem and my account page show that I have found 2 factors. What does this mean exactly? Where can I find the composite number for which I apparently found a factor? Travis

JimB
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Message 83806 - Posted: 7 Mar 2015 | 4:53:13 UTC - in response to Message 83803.

I'm running the Sierpinski Problem and my account page show that I have found 2 factors. What does this mean exactly? Where can I find the composite number for which I apparently found a factor? Travis

You can't. With some projects, like Prime Proth Search (PPS) Sieve, the factors are immediately extracted from the workunits and it's impossible to tell later who found them. That's because there are a great many factors found - about 23 million/month.

For ESP/PSP/SoB sieving, I can look up the factors found and they are at least temporarily still associated with the userid. For example, your entries are:

23768789090323999 is a factor of 99739*2^17688666+1
24556928091959411 is a factor of 229673*2^49384941+1

At some point when a new sieve file is constructed those would be removed entirely from the database. Those candidates wouldn't be in the sieve file any more. We'd keep the factors in a text file, but not the userids of those who found them. The count of factors you've found is in a different table and that number would never decrease.

travismac

Joined: 15 Feb 15
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Message 83819 - Posted: 7 Mar 2015 | 14:39:58 UTC

Many thanks. And, a related question comes to mind. What about the other factor?... meaning the factor that would be multiplied by my found factor to get the product.

As an aside I note that the "Reply" and "Quote" buttons at the bottom of the reply do not work?

JimB
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Message 83820 - Posted: 7 Mar 2015 | 15:03:51 UTC - in response to Message 83819.

Many thanks. And, a related question comes to mind. What about the other factor?... meaning the factor that would be multiplied by my found factor to get the product.

As an aside I note that the "Reply" and "Quote" buttons at the bottom of the reply do not work?

It's quite simple to compute the other factor if we wanted to, but there's not much point to it. It could be either prime or composite, but the latter is more likely in my experience. The reason we test candidates in the form of k*2^n+1 is that it's far faster to do a primality test when the candidate plus or minus 1 is easily factored. A random 5.3-million-digit-number (the dividend on your first factor) is not so quickly or easily tested.

Factors are easily verified and we do so multiple times to make sure any given candidate really is composite before removing it from the sieve.

I used the "Quote" button to create this reply. Both of those buttons work for me and I assume for most other people posting here or I'd have heard about it before now.

travismac

Joined: 15 Feb 15
Posts: 3
ID: 381640
Credit: 120,635
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Message 83826 - Posted: 7 Mar 2015 | 21:41:47 UTC - in response to Message 83820.

Gotcha. Thanks. Post buttons etc seem to work now. I was getting the following msg: