Missed Factors (TF)
 

This thread is intended to collect information about factors obtained with trial factoring (TF) that have been previously missed due to:
1) Incomplete TF scans for small factors;
2) Faulty TF hardware/software;
3) Fake TF reports;
etc.

An example is
M[M]618033947[/M]
for which the 68-bit factor 276413495291788087169 was found.
It was not previously in the GIMPS database and 0.3866 GHz-Days were given for finding it.
Note that zero (0.0000) GHz-Days are given for the TF verification of a known factor.

A second example is

M[M]726064763[/M]

for which three (3) factors (34153055801363324180057, 7170112396664438582504527, and 10702385060027676180416983) have been missed for an unknown reason in previous TF tests.

[QUOTE=Dobri;602995]A second example is

M[M]726064763[/M]

for which three (3) factors (34153055801363324180057, 7170112396664438582504527, and 10702385060027676180416983) have been missed for an unknown reason in previous TF tests.[/QUOTE]
Those were not missed, expect by your examination of the page you linked to.

34153055801363324180057 was reported on 2016-06-14 by Anonymous and 2022-01-21 by LordJulius

2021-12-28 alpertron F-PM1 Factor: 7170112396664438582504527 / (P-1, B1=1000000, B2=10164924)
2021-12-28 Yzzyx F-PM1 Factor: 7170112396664438582504527 / (P-1, B1=1000000, B2=10164924)

2021-12-26 alpertron F-PM1 Factor: 10702385060027676180416983 / (P-1, B1=1000000, B2=1000000)

[QUOTE=Dobri;602994]
M[M]618033947[/M]
for which the 68-bit factor 276413495291788087169 was found.
It was not previously in the GIMPS database and 0.3866 GHz-Days were given for finding it.
Note that zero (0.0000) GHz-Days are given for the TF verification of a known factor.[/QUOTE]It not being in the database does not mean it was missed. It was just not found yet. It had a very small factor and those there was no need to continue looking for more factors. We are trying to eliminate exponents that that we will have to run a primality test on. We are not doing exhaustive factoring on all exponents. And even if we were, it would be a long while before we got to that one.

[QUOTE=Uncwilly;602996]Those were not missed, expect by your examination of the page you linked to.[/QUOTE]
Said factors were already known indeed.
The point is that they were missed in subsequent TF tests.

[QUOTE=Dobri;602994]...
3) Fake TF reports;
An example is
M[M]618033947[/M]
...[/QUOTE]You mean results like :
Factor: 12965740712769703 / TF: 1-53
Factor: 37915764094923857 / TF: 1-53
Factor: 37915764094923857 / TF: 53-54
Factor: 37915764094923857 / TF: 54-55
The first factor is 53,5 bits the second 55,0 bits. How can a 55 bits factor be found trial factoring from 1 to 53 bits ?
I suppose those where tests ?
As for some no factor results, they may be the result of finishing a bit level even after a factor was found, there used to be an option to do that, but now I can only find such a setting about ECM in undoc.txt.

[QUOTE=Dobri;602999]The point is that they were missed in subsequent TF tests.[/QUOTE]

Which "no factor" TF lines missed which factors?

[QUOTE=S485122;603002]You mean results like :
Factor: 12965740712769703 / TF: 1-53
Factor: 37915764094923857 / TF: 1-53
Factor: 37915764094923857 / TF: 53-54
Factor: 37915764094923857 / TF: 54-55
The first factor is 53,5 bits the second 55,0 bits. How can a 55 bits factor be found trial factoring from 1 to 53 bits ?
I suppose those where tests ?[/QUOTE]
The quoted results above were generated by the mfaktc app. Sometimes, mfaktc gives such output.

What I meant was that the user Anton Repko missed 3 factors in their TF 74-75, 82-83, and 83-84 tests.

Yes, that is a bit strange:

[CODE]2022-03-07 Dobri F Factor: 10702385060027676180416983 / TF: 83-84
2022-02-23 Dobri F Factor: 7170112396664438582504527 / TF: 82-83
.
2022-01-21 LordJulius F Factor: 34153055801363324180057 / TF: 74-75
.
2022-01-01 Anton Repko NF no factor from 2^82 to 2^83
2022-01-01 Anton Repko NF no factor from 2^74 to 2^75
.
2021-12-30 Anton Repko NF no factor from 2^83 to 2^84[/CODE]

Currently, in addition to the [COLOR="Blue"]correct[/COLOR] TF results, the server generates also [COLOR="Red"]incorrect[/COLOR] TF results when processing intervals for which [COLOR="blue"]mfaktc[/COLOR] provides both [COLOR="Blue"]prime[/COLOR] and [COLOR="Red"]composite[/COLOR] factors.

For example, see the exponent M[M]54647693[/M] where for TF:67:68 [COLOR="Blue"]mfaktc[/COLOR] provides

one [COLOR="Blue"]prime[/COLOR] factor, 226554856699193904647, interpreted [COLOR="Blue"]correctly[/COLOR] by the server as "[COLOR="blue"]Factor: 226554856699193904647 / TF: 67-68[/COLOR]",

and one [COLOR="Red"]composite[/COLOR] factor, 161694036735902117647, for which the server unnecessarily gives "[COLOR="Red"]no factor from 2^67 to 2^68[/COLOR]".

[QUOTE=ATH;603007]Yes, that is a bit strange:
[/QUOTE]Hardware fails.

Due to the issue described in post #10 at [url]https://mersenneforum.org/showpost.php?p=621165&postcount=10[/url] and some subsequent measures taken at the GIMPS server,
now when LordJulius partially repeats some of his own TF tests (without skipping the composite factor generated by mfaktc), a double TF miss occurs.
For example see the TF: 67-68 tests of M[M]15941603[/M].

[QUOTE=Dobri;623345]Due to the issue described in post #10 at [url]https://mersenneforum.org/showpost.php?p=621165&postcount=10[/url] and some subsequent measures taken at the GIMPS server,
now when LordJulius partially repeats some of his own TF tests (without skipping the composite factor generated by mfaktc), a double TF miss occurs.
For example see the TF: 67-68 tests of M[M]15941603[/M].[/QUOTE]

But if you look at that exponent on mersenne.ca, you see that the 67-68 factor was caught, but that a 'glitch' on the server side resulted in unnecessary second result lines.
This 'glitch' was previously pointed out concerning the Factors Missed by TF page ([url]https://www.mersenne.ca/tfmissed.php?u=173981[/url]), where the reults are all separated by 0-1 second.

The matter is now resolved for new submissions of TF tests with the inclusion of the notification "[COLOR="Blue"]Redundant composite factor[/COLOR]".
For example, see M[M]16897861[/M] for which one more composite factor (TF:1:64) was generated by [COLOR="Blue"]mfaktc[/COLOR] but it was skipped manually and does not appear in the PrimeNet exponent status at the GIMPS server.
[code]M16897861 has a factor: 2096988918560585239 [TF:1:64:mfaktc 0.21 75bit_mul32_gs][/code]

[QUOTE=kriesel;621168]Hardware fails.[/QUOTE]

Geeks often don't get out often... No one notices our work until something /doesn't/ work (which we work hard not to have ever happened).

It's not easy being us. But most of those who do the job actually enjoy it.

It can be fun never being seen. But always there when needed.

I am not alone in that solution space.

A smaller 77-bit factor of M[M]19470709[/M] was just found long after an 80-bit factor was found way back in 2004.
Said 80-bit factor is listed as TF result at [url]https://www.mersenne.ca/exponent/19470709[/url].
However, it is probably P-1 or ECM result instead.