mersenneforum.org  

Go Back   mersenneforum.org > Great Internet Mersenne Prime Search > Data

Reply
 
Thread Tools
Old 2005-09-11, 15:13   #1
jasong
 
jasong's Avatar
 
"Jason Goatcher"
Mar 2005

5×701 Posts
Default How do I determine the xth-highest prime on prime pages?

I'm surfing this prime site, and I'm trying to determine how to find primes of specific ranks.

Is there a method to use if I wanted to find, say, the 4000th-highest prime found?

The reason I ask is that I'm involved in 15k, and it would be nice to be in the top 5000 for six months to a year at least.

Can anybody solve my problem, or give any kind of advice?

Edit: Okay, I figured it out, the magic number of digits to get above 4000 is 64450. Sorry to clog the forums.

Last fiddled with by jasong on 2005-09-11 at 15:20
jasong is offline   Reply With Quote
Old 2005-09-11, 15:18   #2
jinydu
 
jinydu's Avatar
 
Dec 2003
Hopefully Near M48

110110111102 Posts
Default

You can download the complete list of the top 5000 largest known primes here:

http://primes.utm.edu/primes/download.php
jinydu is offline   Reply With Quote
Old 2005-09-11, 15:42   #3
paulunderwood
 
paulunderwood's Avatar
 
Sep 2002
Database er0rr

2×1,723 Posts
Default

http://primes.utm.edu/primes/search.php

gives you many options to refine a search...

Last fiddled with by paulunderwood on 2005-09-11 at 15:42
paulunderwood is offline   Reply With Quote
Old 2005-09-11, 23:28   #4
Numbers
 
Numbers's Avatar
 
Jun 2005
Near Beetlegeuse

22·97 Posts
Default

You can of course also work it out for yourself. The probability that n is prime is approx. 1/Log(n), so the nth prime is approx. n * Log(n).
Approx. means that when n = 10^11 the error is about 8%, which will at least put you in the right ballpark.
Numbers is offline   Reply With Quote
Old 2005-09-11, 23:42   #5
jinydu
 
jinydu's Avatar
 
Dec 2003
Hopefully Near M48

2·3·293 Posts
Default

Quote:
Originally Posted by Numbers
You can of course also work it out for yourself. The probability that n is prime is approx. 1/Log(n), so the nth prime is approx. n * Log(n).
Approx. means that when n = 10^11 the error is about 8%, which will at least put you in the right ballpark.
He meant the x-th largest known prime, not the x-th prime.

For instance, the first largest known prime is M42.
jinydu is offline   Reply With Quote
Old 2005-09-12, 08:04   #6
Numbers
 
Numbers's Avatar
 
Jun 2005
Near Beetlegeuse

22·97 Posts
Default

Doh....

(we need a smiley in the form of Homer for occasions like this)

Last fiddled with by Numbers on 2005-09-12 at 08:05 Reason: mis-spelling
Numbers is offline   Reply With Quote
Old 2005-09-12, 12:26   #7
R.D. Silverman
 
R.D. Silverman's Avatar
 
Nov 2003

26·113 Posts
Thumbs up

Quote:
Originally Posted by jasong
I'm surfing [url=http://primes.utm.edu/]

<snip>
"Is there a method to use if I wanted to find, say, the 4000th-highest prime found?"

The short answer is no.

(1) What you seek is a moving target. It changes all the time.

(2) A yes answer would be predicated on assuming that all such known
primes have been *reported* and furthermore, have been *displayed*
in a public website. This can not be assumed.

"it would be nice to be in the top 5000 for six months to a year at least."

Why? What value does it have? I don't understand what value it would
have to you. *IF* you had written the code to find such a prime, then
you could be very proud of such a discovery. But blindly running black box
code written by others has very little value, at least IMO.

It is true that I use the CWI post-processing suite for my NFS work.
However, I have written my own post-processing code, except for the
final square root. I use the CWI suite because it is substantially better.
(although my Block Lanczos code is nearly as fast as theirs). I simply
do not have the time to optimize all of the code that I have written.
They also use a better algorithm for filtering (cliques) than I do (intelligent
Gaussian elimination).

I would have more respect for your prime-hunting efforts if you would at least
*TRY* to write your own code, even if it is inefficient.

Finding large primes is a relatively *easy* problem, because they are
abundant. Why don't you try something HARD?
R.D. Silverman is offline   Reply With Quote
Old 2005-09-13, 20:41   #8
jasong
 
jasong's Avatar
 
"Jason Goatcher"
Mar 2005

5×701 Posts
Default

Quote:
Originally Posted by R.D. Silverman
"Is there a method to use if I wanted to find, say, the 4000th-highest prime found?"

The short answer is no.

(1) What you seek is a moving target. It changes all the time.

(2) A yes answer would be predicated on assuming that all such known
primes have been *reported* and furthermore, have been *displayed*
in a public website. This can not be assumed.
That's a good point, although I've found these types of answers annoy most people(I know this because I've given similar type answers in the past)\

Quote:
Originally Posted by R.D. Silverman
"it would be nice to be in the top 5000 for six months to a year at least."

Why? What value does it have? I don't understand what value it would
have to you. *IF* you had written the code to find such a prime, then
you could be very proud of such a discovery. But blindly running black box
code written by others has very little value, at least IMO.

It is true that I use the CWI post-processing suite for my NFS work.
However, I have written my own post-processing code, except for the
final square root. I use the CWI suite because it is substantially better.
(although my Block Lanczos code is nearly as fast as theirs). I simply
do not have the time to optimize all of the code that I have written.
They also use a better algorithm for filtering (cliques) than I do (intelligent
Gaussian elimination).

I would have more respect for your prime-hunting efforts if you would at least
*TRY* to write your own code, even if it is inefficient.

Finding large primes is a relatively *easy* problem, because they are
abundant. Why don't you try something HARD?
Hard in terms of math, or hard in terms of new experiences? The hardest problem I have in my life is getting a girlfriend, my anxiety disorder has prevented me from doing that since I was seventeen. Achieving that would be preferable to even a top-20 prime.
jasong is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Highest Prime is also a twin prime... NOT hydeer Lone Mersenne Hunters 9 2018-04-03 22:54
Prime Pages How to's PawnProver44 Information & Answers 29 2016-03-15 05:43
TPS prime pages password Oddball Twin Prime Search 5 2011-03-20 04:50
What's up with the Prime Pages? Unregistered Information & Answers 1 2007-06-09 02:44
Project where the goal is to get the highest Prime Pages score. jasong Lounge 4 2006-08-22 21:04

All times are UTC. The time now is 11:36.

Wed Oct 28 11:36:49 UTC 2020 up 48 days, 8:47, 2 users, load averages: 1.79, 1.81, 1.75

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.