Hi all,

Daniel Swanson wrote:
> 7019297  57  DF  160100125459121849  27-Sep-01 22:52
> 7020641  58  DF  226230108157229263  30-Sep-01 02:05
> 7025987  56  DF   74052063365823791  30-Sep-01 01:12
> 7027303  55  DF   31090234297428433  30-Sep-01 22:14
> 7028947  58  DF  203918491658210359  01-Oct-01 03:11
> 7033963  56  DF  100945633281264553  03-Oct-01 07:36
> 7036409  58  DF  321885922408857601  04-Oct-01 02:54

'ribwoods' wrote:
> I'm pretty sure the second column is the previous trial-factoring
> limit, in units of power-of-2.

Actually, when a factor is found, the primenet server returns the size
of the factor in bits, but it rounds the value Log2(factor)
mathematically to the next integer and not always upwards what would
make more sense. Therefore the factor can be bigger than 2^n shown in
the second column.

There are some people doing broadband factoring, what means that they
extend the factoring limit on a big range of numbers by 1 or a few bits
using the factoroverride option. Hence, it is very likely, that the
fault happened during that process and not by the person who was doing
the first LLTest (At that time the P-1 Test was not available yet, and
the factoring limit beyond the factor).
While completing some trial factoring in the 60 million range I noticed,
that the prime95 checksum of factoring from 65 to 66 bits and from 66 to
68 bits are the same (I did this two parts of the same exponent on
different computers). That means that it is easily possible that some
mistakes can happen, when someone writes the 'Factor=' line into the
worktodo file. Another reason might be, that one person ran a broadband
factoring range from 55 to 58 bits on one computer, from 58 to 59 on
another (to split up the work) and forgot to check in the former
results. As there is no information about the starting bit in the result
file, the primenet server is not able to detect that problem.

I think the easiest way to fix this problem is to recheck these ranges,
which were completed by the user(s) where more than one factor appeared.
As the server also logs the id, that would not be too difficult to
realize.

Probably that problem might become worse in future:
George told me, that primenet  shows the clients, that a p-1 is already
done, by adding 0.5 to the factoring limit. Prime95 detects that
correctly, but in the reports these values are rounded to the next digit
(64.5 -> 65 and so on). If someone takes the factoring information from
these lists, if would cause a gap of one bit in the factoring process. I
suggest to change the rounding behavior of the primenet server or to
decrease the value which indicates a completed p-1 test from 0.5 to 0.4.

I hope that we will find the missing factors without too much effort.

Regards,

Reto


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