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Thread: factor missed by sieving

  1. #1
    Senior Member Frodo42's Avatar
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    factor missed by sieving

    I think we had another discussion about something similar to this somewhere, but I can't find it so I'll start a new.

    I just found this

    P-1 found a factor in stage #2, B1=30000, B2=292500.
    4847*2^7411287+1 has a factor: 25606348911511

    This factor should have been found been found by sieving long ago.

    Someone mentioned that the some version of the siever had missed a few factors, but this range is too low to have been sieved with the mentioned siever as I remember it.

    The range it should have been found in is:
    25600 25650 Netbrian

    Could it be that there are more factors to find by resieving this range or is this just a single miss?

  2. #2
    Sieve it, baby!
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    Just tested it with proth_sieve 0.42 - factor is found.

    How about resieving Netbrian's range to check if other factors are missed? I could do this quickly (< 1 day)...

  3. #3
    Senior Member Frodo42's Avatar
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    Originally posted by Mystwalker
    Just tested it with proth_sieve 0.42 - factor is found.

    How about resieving Netbrian's range to check if other factors are missed? I could do this quickly (< 1 day)...
    That would probably be a good idea, just go ahead and do that.

    If there are more factors here it could be that Netbrians other ranges also should be checked.

  4. #4
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    Ok, started computation...
    ETA: 3 hours

  5. #5
    Moderator vjs's Avatar
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    I had a quick question about sieve vs P-1

    If for example a k/n pair has a factor within the sieve range of 2^49-2^50 could this factor be missed by P-1???

    I know that sieve and P-1 are different animals, sieve is basically trial division so if there is a factor in the range sieve will find it. But I'm not exactly sure how P-1 works if there is a factor in that range (2^49-2^50) is P-1 guarenteed to find the factor?

  6. #6
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    P-1 will only find a factor if (P-1) - with P as the factor - is smooth, which means that (P-1) is (highly) composite and all of its factors are very small*.

    *all factors have to be < B1, except one factor, which may be < B2.


    ETA Update: still 2 hours...
    no additional factors found yet

  7. #7
    Unholy Undead Death's Avatar
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    no new factors or no factors at all?
    wbr, Me. Dead J. Dona \


  8. #8
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    No new factors - but meanwhile, there are some:

    25608226881791 | 10223*2^16324409+1
    25618827138587 | 4847*2^10937991+1

    2 of the results were new results and saved to the database.

  9. #9
    Moderator vjs's Avatar
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    all factors have to be < B1, except one factor, which may be < B2
    Interesting, I didn't understand what the b1, b2 values meant perhaps this should be included in the p-1 reservations section.

    So basically you want to keep b1 and b2 as high as posssible.

    When I did my range I tryed to keep b1 low and b2 high...

    Which was obviously the wrong thing to do (b1 low)... well at least I found one factor.

  10. #10
    Moderator vjs's Avatar
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    Netbrains ranges:

    1800 - 1850 50 644 87 0 1177.076
    4350 - 4399 49 253 38 0 1108.356
    6350 - 6400 50 184 44 0 1175.531
    7700 - 7750 50 149 33 0 1153.169
    8900 - 8950 50 121 21 0 1081.705
    9050 - 9100 50 104 25 0 945.777
    9650 - 9700 50 120 17 0 1162.489
    11610 - 11650 40 79 18 0 920.949
    12230 - 12300 70 141 33 0 1732.428
    13800 - 13850 50 66 12 0 913.728
    15100 - 15150 50 57 19 0 864.624
    15155 - 15200 45 63 18 0 958.733
    15300 - 15350 50 76 18 0 1167.512
    15850 - 15900 50 63 18 0 1002.767
    16100 - 16150 50 65 18 0 1050.604
    21230 - 21300 70 49 9 3 1044.181
    22640 - 22700 60 31 4 4 703.487
    25600 - 25650 50 32 9 3 822.362
    26750 - 26800 50 15 8 3 403.778
    27000 - 27050 50 12 4 5 325.054
    27700 - 27750 50 37 5 0 1027.320
    32000 - 32050 50 28 7 0 898.945
    32630 - 32700 70 36 12 0 1179.682
    39450 - 39500 50 33 6 0 1305.043
    40800 - 40850 50 26 5 0 1063.494
    42600 - 42650 50 20 5 1 854.580
    42900 - 42950 50 13 4 3 559.666
    43400 - 43450 50 16 5 2 8.684

    Total 1454G

    Your right some of them look interesting...

    I'll start retest,

    25600-25650 Mystwalker (complete) no additional through sieve
    26750-26800 VJS
    27000-27050 VJS

    Or were you stating that you would retest all of them?

    LMK I already started the range but I could stop, should have these finished by tommorrow

    These also look interesting:

    11610-11650
    15100-15150
    42900-42950
    43400-43450
    Last edited by vjs; 11-08-2004 at 01:59 PM.

  11. #11
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    Sieving complete, no additional previously-unknown factors found

    Or were you stating that you would retest all of them?
    I only meant that specific one. Maybe I'll retest others in the next days, but I wait until maybe some results show up and only after having reserved here.

    25600-25650 Mystwalker (complete) no additional through sieve
    26750-26800 VJS
    27000-27050 VJS
    You seem to have picked the most likely (read: "underpopulated") ranges. I did a quick check, including factor density:
    Code:
    Start	End	Size	Factors	Factors / G	Corrected Factors / G (=Start*Factors/(10000*rangeSize))
    1800	1850	50	644	12.88		2.32
    4350	4399	49	253	5.16		2.25
    6350	6400	50	184	3.68		2.34
    7700	7750	50	149	2.98		2.29
    8900	8950	50	121	2.42		2.15
    9050	9100	50	104	2.08		1.88
    9650	9700	50	120	2.4		2.32
    11610	11650	40	79	1.98		2.29
    12230	12300	70	141	2.01		2.46
    13800	13850	50	66	1.32		1.82
    15100	15150	50	57	1.14		1.72
    15155	15200	45	63	1.4		2.12
    15300	15350	50	76	1.52		2.33
    15850	15900	50	63	1.26		2
    16100	16150	50	65	1.3		2.09
    21230	21300	70	49	0.7		1.49
    22640	22700	60	31	0.52		1.17
    25600	25650	50	32	0.64		1.64
    26750	26800	50	15	0.3		0.8
    27000	27050	50	12	0.24		0.65
    27700	27750	50	37	0.74		2.05
    32000	32050	50	28	0.56		1.79
    32630	32700	70	36	0.51		1.68
    39450	39500	50	33	0.66		2.6
    40800	40850	50	26	0.52		2.12
    42600	42650	50	20	0.4		1.7
    42900	42950	50	13	0.26		1.12
    43400	43450	50	16	0.32		1.39
    Next interesting would be:
    Code:
    42900	42950	50	1.12
    22640	22700	60	1.17
    43400	43450	50	1.39
    21230	21300	70	1.49
    25600	25650	50	1.64
    32630	32700	70	1.68
    42600	42650	50	1.7
    15100	15150	50	1.72
    32000	32050	50	1.79
    13800	13850	50	1.82
    9050	9100	50	1.88
    Btw.:
    "25600-25650 Mystwalker (complete) no additional through sieve" <-- I found 2 additional factors, frodo 1, so there were 3
    Last edited by Mystwalker; 11-08-2004 at 02:23 PM.

  12. #12
    Moderator vjs's Avatar
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    read: "underpopulated") ranges
    Do you have a link???

    Yes I did a quick "look see" at the numbers and those looked promising, thanks for your table.

    I also looked at some other users and how many factors they recieved in near-by ranges to see if (0.3 f/G) was reasonable


    <del>

    But it looks like anything with a factors/G of <0.4 is questionable. But anything with factors/G >0.4 is probably O.K.

    Perhaps this has been done already etc. I'll make up another table of questionable in a few minutes.
    Last edited by vjs; 11-08-2004 at 04:07 PM.

  13. #13
    Moderator vjs's Avatar
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    O.K. new table,
    paramters for table
    Only ranges <2^48
    Only range sizes >50G
    CF < ~1.2 (I used a value simlar to your CL)
    CL - Confidence level - Instead of 10000 it's something smaller but same formula


    Here is the table, it's note worthy to see that some popular names are included
    mklasson for example
    as well as frodo42

    CL CF Fact/G Start Stop Range Fact Excl Dup Name
    21.0 0.26 0.010 262400 262500 100 1 0 0 Troodon
    40.0 0.50 0.160 31250 31300 50 8 0 0 jmblazek
    40.6 0.51 0.020 254000 254100 100 2 0 0 alexr
    40.8 0.51 0.020 254950 255000 50 1 0 0 Troodon
    43.1 0.54 0.169 31870 32000 130 22 0 0 jmblazek
    51.8 0.65 0.240 27000 27050 50 12 4 5 netbrian
    53.4 0.67 0.060 111200 111250 50 3 0 0 rosebud
    59.6 0.75 0.185 40300 40500 200 37 1 0 jmblazek
    63.5 0.79 0.030 264500 264600 100 3 0 16 frodo42
    64.2 0.80 0.300 26750 26800 50 15 8 3 netbrian
    65.4 0.82 0.036 227000 227500 500 18 1 0 expmod8
    66.6 0.83 0.110 75700 75800 100 11 5 0 Foobar
    67.5 0.84 0.055 153300 153500 200 11 0 0 hc_grove
    67.7 0.85 0.040 211500 211600 100 4 0 0 frodo42
    69.0 0.86 0.032 269500 269750 250 8 13 277 royanee
    73.0 0.91 0.060 152000 152100 100 6 0 0 Deoje362 (Deoje)
    73.3 0.92 0.130 70500 70600 100 13 2 1 jimmy
    79.2 0.99 0.180 55000 55050 50 9 4 0 Moothecow (Moo_the_co
    81.0 1.01 0.050 202500 202600 100 5 0 0 Tully
    81.6 1.02 0.060 170100 170300 200 12 4 216 Joe_O
    82.8 1.03 0.456 22710 22800 90 41 6 3 cmprince
    84.2 1.05 0.045 234000 234200 200 9 5 241 BigMajaX
    85.0 1.06 0.071 148800 149500 700 50 8 0 expmod8
    85.4 1.07 0.040 266850 267500 650 26 0 0 darkman
    85.7 1.07 0.070 153000 153100 100 7 4 62 Deoje362 (Deoje)
    88.0 1.10 0.400 27500 27600 100 40 0 0 jmblazek
    88.3 1.10 0.280 39400 39450 50 14 6 114 mklasson
    88.3 1.10 0.120 92000 92050 50 6 3 179 BigMajaX
    89.2 1.12 0.260 42900 42950 50 13 4 3 netbrian
    93.2 1.16 0.541 21520 21605 85 46 19 6 louie
    93.6 1.17 0.517 22640 22700 60 31 4 4 netbrian
    94.7 1.18 0.690 17150 17250 100 69 2 6 ceselb
    95.5 1.19 0.280 42650 42700 50 14 1 1 mklasson
    97.0 1.21 0.240 50500 50550 50 12 1 3 jimmy
    97.1 1.21 0.053 229000 230000 1000 53 1 0 priwo
    97.6 1.22 0.049 247250 248000 750 37 1 0 Mat67
    97.7 1.22 0.070 174400 174500 100 7 7 171 jimmy
    97.8 1.22 0.080 152800 152900 100 8 6 222 Mischa
    98.4 1.23 0.057 215150 215500 350 20 0 0 darkman

    Can someone modify this table so it looks good, don't know how to Code: etc.

    I'm also not sure how accurate CL/CF is when it comes to larger p values >>281T and of course small ranges produce more error in the calculated CL/CF. So alot of ranges were not included in this table some obviously had small ranges ~10G and 2 or less factors, they ranked very high of course.
    Last edited by vjs; 11-08-2004 at 05:51 PM.

  14. #14
    Moderator Joe O's Avatar
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    As per usual, I will redo my own range:

    81.6 1.02 0.060 170100 170300 200 12 4 216 Joe_O
    Joe O

  15. #15
    Moderator vjs's Avatar
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    Joe_O,

    I wouldnt redo your range unless your thinking that there may be a problem there.
    Also before we start distributing these we should infact make a double check thread.

    You have a CL of ~80 with a fairly large p, I don't think there are missed factors there.

    If you'd like to recheck a range do

    31870-32000 jmblazek

    It looks like a much greater offender than yours,

    I'm going (31250-31300 jmblazek) already to see if the theory holds.

  16. #16
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    Originally posted by vjs
    Do you have a link???
    Link?
    I draw that conclusion from the table I offered afterwards...

    But it looks like anything with a factors/G of <0.4 is questionable. But anything with factors/G >0.4 is probably O.K.
    As factor density decreases, it's important to multiply the density with the range depth (start or end - I found out that it basically makes no real difference). So when a desity for depth x is acceptable, it's density/2 for 2*x...
    Last edited by Mystwalker; 11-09-2004 at 09:26 AM.

  17. #17
    Moderator vjs's Avatar
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    link?
    I just wanted to read how one came up with the =Start*Factors/(10000*rangeSize)

    The table does draw its own conclusions pretty well.

    Anyways I was thinking it should be something like start^1.05 or some other very small exponent b/c it does break down above 2^48.

    But more importantly, I've checked most of the 27000-27050 last night before I lost power and havn't found any new factors in fact.txt.

    However I did find about 400 new results in factexcl.txt from the 500 I submitted and 1 new result factrange.txt from the 17 of 44 verified.

    I will continue with the following two ranges

    31250-31300

    and

    26750-26800

    But I don't think anything will be found there that is both new and important, but I will keep all informed.

    I think this double checking thread is at least one reason why factexcl.txt should be included in submissions.

  18. #18
    Sieve it, baby!
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    Originally posted by vjs
    I just wanted to read how one came up with the =Start*Factors/(10000*rangeSize)
    It was just my very own spontaneous idea...

    It started with Factors/rangeSize - but as we have to think of the decreasing factor density, I added the multiplier "Start" to even this out. And the 10000, well, that's only to get good-looking numbers...

  19. #19
    Moderator vjs's Avatar
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    31250-31300 Completed double check no new factors in fact.txt
    27000-27050 Completed double check no new factors in fact.txt

    Well I complete these two ranges found alot of new factors in factexcl.txt and factrange.txt but nothing in fact.txt.

    Regardless I submitted all of these factors even tough they were dups.

    I'm going to consider that the rest of these ranges are correct and not worth the time nor energy to redo, even though they look promissing.

    Probably be better off doing supersecret double checks etc not double check sieve.

    Hopefully this will bring this thread to a close.

  20. #20
    Senior Member Frodo42's Avatar
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    OK I found another weird factor using P-1

    23171537407129 | 10223*2^8341577+1

    for one thing it should have been found by sieving long ago.

    The other is that it doesn't seem to want to submit to result.txt it doesn't show up in the scores and I can't find it in results.txt.
    It does get verified and the first time I submitted it, it did say it was added to the database.
    It could be there is a few more factors.

    Anyways I'm not sure this is worth resieving ... the factor should be found in this range

    23170 23200 Troodon

    I think (unless I counted the number of digits wrong here)

  21. #21
    Moderator vjs's Avatar
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    O.K. I'll resieve that range...

    Please do not resieve any of the ranges less than 75T at this moment, or if you must please contact Joe_O or myself before doing so...

    Also thanks Frodo, if any of you P1 guys find missing factors that should have been found through sieve let us know asap.

    BTW is it worth making a double check sieve thread for any of these resieves???

    Just to report reservations only...

    Jason

    23170 23200 Troodon [Double Check by VJS]

    I'll have it done by tommorrow and report my findings.

    Last edited by vjs; 01-18-2005 at 10:02 AM.

  22. #22
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    The other is that it doesn't seem to want to submit to result.txt it doesn't show up in the scores and I can't find it in results.txt.
    That's because it's too low to show up on the results.txt - only factors above 25T.

    I'll manually add your find to my low results file, then you'll get credit. Unfortunately it's below 40T, so it won't score much. Sorry.

  23. #23
    Moderator vjs's Avatar
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    Mike, There is another factor in that range <20M

    it's not pressing... Joe will send it to you.

  24. #24
    Senior Member Frodo42's Avatar
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    Originally posted by MikeH
    That's because it's too low to show up on the results.txt - only factors above 25T.

    I'll manually add your find to my low results file, then you'll get credit. Unfortunately it's below 40T, so it won't score much. Sorry.
    Well that doesn't matter to much, what is important to me is that is won't be handed out, but since I submitted it via. the form I hope that's been taken care of.
    But thanks anyway.

  25. #25
    Moderator vjs's Avatar
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    23170 23200 Troodon [Double Check Completed by VJS] 1 extra factor at 19M plus frodos factor

  26. #26
    Moderator vjs's Avatar
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    This has come up in another thread so I would ask that nobody double check sieve ranges less than 26000, (26000G or 26T), consider them already checked or that someone is investigating them "already reserved", I will report progress...


    0-26000G [Reserved or Completed]


    I would also ask that anyone finding factors through P-1 in/within a range that has already been sieve report it here. I'm generally keeping tab's etc but you never know.

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