mersenneforum.org Which are the "worst" drivers?
 Register FAQ Search Today's Posts Mark Forums Read

 2012-06-24, 15:06 #1 Dubslow Basketry That Evening!     "Bunslow the Bold" Jun 2011 40
2012-06-24, 19:44   #2
Batalov

"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

2×37×127 Posts
Which are the "worst" drivers?

Reminds me of a trick question:
Quote:
 Q: How can you spot an intoxicated Asian Female driver? A: You can't!

2012-06-24, 23:34   #3
science_man_88

"Forget I exist"
Jul 2009
Dumbassville

26×131 Posts

Quote:
 Originally Posted by Dubslow So I'm sure we've all read Clifford's analysis page. (Btw, I've created a mirror of that page and his "From the Trenches" page so that we don't have to deal with the archive, and so that someone could edit it should they feel so inclined. Of course, if Clifford makes his own comeback, I'll take these down.) Anyways, the analysis classifies the drivers by their characteristics, by how "stable" they are. Of course, that doesn't take into account other factors, like how much a driver increases a sequence, or how rare getting a 127^2 is. So, since I am not an expert (or even half-competent) in these matters, I'm asking: Is it possible to create an ordered list of drivers from "worst to first"? Obviously the downdriver would be "first". I imagine 2^2 would be next, followed by 2^3, since they tend to drop a sequence, albeit slowly (and they're not very stable). Code: Best 2 2^2 2^3 ... ? ... 2^6 * 127 ?? Worst (PS Are there any drivers which are missing from that table?)
Code:
for(a=1,60,for(b=1,#divisors(sigma(2^a)),if(sigma(divisors(sigma(2^a))[b])%(2^(a-1))==0,print(2"^"a"*"divisors(sigma(2^a))[b]))))
according to this code:

Quote:
 2^1*1 2^1*3 2^2*7 2^3*3 2^3*15 2^4*31 2^5*21 2^6*127 2^9*1023 2^12*8191 2^16*131071 2^18*524287 2^30*2147483647 2^60*2305843009213693951
are all drivers but not all of the possible drivers, partly because I can't search higher how I have things set up. the bigger a driver is the rarer it likely is. as to biggest gains I would think the larger ones but all I know is possibly with numbers that are driver * prime.

Last fiddled with by science_man_88 on 2012-06-24 at 23:43

 2012-06-24, 23:55 #4 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 13·491 Posts Here's an analysis over the 115-to-125-digit elements of all the sequences I've run: a.b.c.d.e means 2^a * 3^b * 5^c * 7^d * 31^e Numbers in brackets at the beginning are the number of lines I saw with that exponent combination. The first probability is the chance of going from one exponent-set to another, so a measure of stability. Numbers in brackets at the end are the average change in log(K) of such lines. So: powers of three are the annoying ones, the worst driver for making sequences get larger is 2^2*3^2*5, 2^3*3 is beautifully stable and drives terms up fast. Powers of two with no other small primes get less stable as the exponent increases. Code: 1.0.0.0.0 (564) 0.901 1.0.0.0.0 (-0.245) 0.053 1.0.1.0.0 (-0.262) 0.023 1.0.0.0.1 (-0.242) 1.0.1.0.0 (99) 0.586 1.0.1.0.0 (-0.054) 0.263 1.0.0.0.0 (-0.044) 0.111 1.0.2.0.0 (-0.016) 1.1.0.0.0 (433) 0.857 1.1.0.0.0 (0.045) 0.046 1.1.1.0.0 (0.041) 0.032 1.2.0.0.0 (0.018) 1.1.1.0.0 (69) 0.507 1.1.1.0.0 (0.180) 0.304 1.1.0.0.0 (0.171) 1.2.0.0.0 (209) 0.756 1.2.0.0.0 (0.108) 0.057 1.1.0.0.0 (0.094) 0.057 1.3.0.0.0 (0.101) 1.2.1.0.0 (60) 0.700 1.2.1.0.0 (0.226) 0.217 1.2.0.0.0 (0.232) 1.3.0.0.0 (91) 0.692 1.3.0.0.0 (0.132) 0.132 1.2.0.0.0 (0.108) 2.0.0.0.0 (2003) 0.846 2.0.0.0.0 (-0.078) 0.057 2.0.1.0.0 (-0.082) 0.024 2.0.0.0.1 (-0.079) 2.0.0.0.1 (67) 0.776 2.0.0.0.0 (-0.049) 2.0.1.0.0 (414) 0.580 2.0.1.0.0 (0.085) 0.280 2.0.0.0.0 (0.078) 0.075 2.0.2.0.0 (0.075) 0.031 2.0.1.0.1 (0.076) 2.0.2.0.0 (84) 0.321 2.0.2.0.0 (0.124) 0.286 2.0.0.0.0 (0.103) 0.274 2.0.1.0.0 (0.110) 2.1.0.0.0 (1130) 0.795 2.1.0.0.0 (0.156) 0.052 2.0.0.0.0 (0.143) 0.045 2.2.0.0.0 (0.140) 0.039 2.1.1.0.0 (0.149) 0.022 2.1.0.0.1 (0.161) 0.019 2.3.0.0.0 (0.149) 2.1.1.0.0 (209) 0.574 2.1.1.0.0 (0.277) 0.278 2.1.0.0.0 (0.273) 0.096 2.1.2.0.0 (0.273) 0.014 2.1.3.0.0 0.010 2.1.0.0.1 0.010 2.2.1.0.0 0.010 2.1.1.0.1 0.005 2.1.1.0.2 0.005 2.2.0.0.0 2.1.2.0.0 (53) 0.321 2.1.2.0.0 (0.300) 0.245 2.1.0.0.0 (0.312) 0.226 2.1.1.0.0 (0.294) 2.2.0.0.0 (432) 0.650 2.2.0.0.0 (0.218) 0.086 2.1.0.0.0 (0.203) 0.049 2.0.0.0.0 (0.195) 0.049 2.2.1.0.0 (0.216) 0.046 2.3.0.0.0 (0.196) 2.2.1.0.0 (106) 0.500 2.2.1.0.0 (0.339) 0.274 2.2.0.0.0 (0.338) 2.3.0.0.0 (130) 0.538 2.3.0.0.0 (0.231) 0.154 2.2.0.0.0 (0.220) 0.123 2.1.0.0.0 (0.211) 3.0.0.0.0 (975) 0.907 3.0.0.0.0 (-0.014) 0.029 3.0.0.0.1 (-0.013) *0.021 2.0.0.0.0* (-0.052) *0.019 4.0.0.0.0* (-0.049) 3.0.1.0.0 (265) 0.879 3.0.1.0.0 (0.130) 0.049 3.0.2.0.0 (0.133) 3.0.2.0.0 (58) 0.621 3.0.2.0.0 (0.155) 0.293 3.0.1.0.0 (0.154) 3.1.0.0.0 (572) 0.946 3.1.0.0.0 (0.217) 0.024 3.1.0.0.1 (0.209) 3.1.1.0.0 (178) 0.888 3.1.1.0.0 (0.331) 0.073 3.1.2.0.0 (0.315) 3.2.0.0.0 (179) 0.771 3.2.0.0.0 (0.263) 0.067 3.1.0.0.0 (0.274) 3.3.0.0.0 (75) 0.587 3.3.0.0.0 (0.291) 0.160 3.2.0.0.0 (0.258) 4.0.0.0.0 (443) 0.767 4.0.0.0.0 (0.018) 0.077 4.0.1.0.0 (0.016) *0.027 3.0.0.0.0* (-0.019) 4.0.0.0.1 (129) 0.860 4.0.0.0.1 (0.051) 4.0.1.0.0 (132) 0.583 4.0.1.0.0 (0.160) 0.265 4.0.0.0.0 (0.142) 4.1.0.0.0 (216) 0.782 4.1.0.0.0 (0.239) 0.060 4.0.0.0.0 (0.208) 0.051 4.2.0.0.0 (0.232) 4.1.0.0.1 (109) 0.798 4.1.0.0.1 (0.266) 4.2.0.0.0 (64) 0.625 4.2.0.0.0 (0.299) 0.172 4.1.0.0.0 (0.281) 4.2.0.0.1 (53) 0.604 4.2.0.0.1 (0.303) 5.0.0.0.0 (247) 0.745 5.0.0.0.0 (0.054) 5.1.0.0.0 (151) 0.828 5.1.0.0.0 (0.280) 0.093 5.1.1.0.0 (0.264) 6.0.0.0.0 (179) 0.721 6.0.0.0.0 (0.036) 6.1.0.0.0 (60) 0.750 6.1.0.0.0 (0.248)
 2012-06-25, 00:12 #5 Dubslow Basketry That Evening!     "Bunslow the Bold" Jun 2011 40
 2012-06-25, 06:20 #6 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 13×491 Posts This is, you will be unsurprised to hear, the output from a perl script run over /home/nfsworld on my large machine (17 megabytes, 87klines); it could relatively easily be rearranged. I'm not quite sure to what extent the probabilities vary with number size (obviously, since the files I'm using to test include the output from the work in http://www.mersenneforum.org/showpos...&postcount=252, I have rather more lines for numbers of size 115-125 digits). I would suggest working out what sort of HTML output you want, making a couple of lines of example, and I'll change the perl (the alternative is that I put a large .tgz file of aliquot-sequence-output and the perl up on www.fivemack.org somewhere and you can do the stats yourself). But I am very busy this week. Last fiddled with by fivemack on 2012-06-25 at 06:22
 2012-06-25, 20:11 #7 Dubslow Basketry That Evening!     "Bunslow the Bold" Jun 2011 40
 2012-07-21, 23:18 #8 Dubslow Basketry That Evening!     "Bunslow the Bold" Jun 2011 40
2012-07-22, 05:39   #9
schickel

"Frank <^>"
Dec 2004
CDP Janesville

84A16 Posts

Quote:
 Originally Posted by Dubslow Look what I found http://www.mersenneforum.org/showthread.php?t=12597 Greebley! (fivemack...?)

I think drivers could actually be considered bad or persistent, or both. Bad would be in terms of increasing the size of a sequences; persistent would be in terms of chances of escape.

For example, how would you characterize this upward run (starting at ~i5154)?

Hint: It's 2^6 * 127 all the way.....
Attached Thumbnails

 Similar Threads Thread Thread Starter Forum Replies Last Post MooMoo2 Other Chess Games 5 2016-10-22 01:55 wildrabbitt Miscellaneous Math 11 2015-03-06 08:17 James Heinrich Software 2 2005-03-19 21:58 nitai1999 Software 7 2004-08-26 18:12

All times are UTC. The time now is 19:37.

Thu Apr 22 19:37:44 UTC 2021 up 14 days, 14:18, 0 users, load averages: 1.52, 1.69, 1.85