[QUOTE=Madpoo;423166]The milestones page shows 81,788 exponents remaining to be first-time checked below M49.

If we further estimate that 5% of the 554,000 that need double-checking below M49 will be bad, that's another ~27,700 that we may as well treat as if they weren't done at all yet.[/QUOTE]

Thanks - so all but ~110,000 (i.e. roughly 90%) of the primes in the interval have already been taken out of consideration, thus my estimate drops to around 0.07 expected primes, which is even more pessimistic than Mini-Geek's.

[QUOTE=Batalov;423157]All the bicycles are invented a long time ago, dudes... :rolleyes:
[CODE]# time ../pfgw64.exe -od -q"2^74207281-1" > M49
PFGW Version 3.7.9.64BIT.20141125.x86_Dev [GWNUM 28.7]

[COLOR=Green]11.364u[/COLOR] 0.220s 0:10.73 107.9% 0+0k 0+43648io 0pf+0w

@ wc M49
1 2 22338669 M49

# cut -c-50 M49
2^74207281-1: 300376418084606182052986098359166050
[/CODE][/QUOTE]

If you already know what number you want, that's nice (low effort). But it doesn't let you easily search in the whole 74M range for the right one: at 11 seconds per number (I'm assuming that searching the file to see if the hints match is trivial), with ~20,000 numbers, that's 2.5 CPU days.

I looked back over the thread, and realized I ignored a useful clue: that the exponent contains "42". That, along with parallelizing my code, cut the time down to 35 minutes. Then I found a list of exponents with [URL="http://www.mersenne.org/report_factors/"]known factors[/URL], that cut it down to 2689 candidates, which [URL="http://pastebin.com/R9gSgnbL"]I can search[/URL] in about 12 minutes.

[QUOTE=ewmayer;423164]Using 906644 odd primes ...[/QUOTE]

You're including all primes, which isn't what I did. I used the stats at [url]http://www.mersenne.org/primenet/[/url] to try to take into account known factors and LLs (of the various kinds, and their accuracy: e.g. LL-D is sure, LL-ERR I counted as 50/50). So I think it's accurate to say that before we searched any, we should expect 0.683 in the range, but since we've LL'd the bulk of it, we only expect 0.18 [I]more[/I] primes in the range.

(I used the (e^gamma/log 2) * log log x formula from your link, and took the simplification of assuming that all numbers in the range had equal probability to be prime; since more of the earlier ones were LL'd, that means my 0.18 is a bit of an overestimate...Edit: Didn't see your more recent post until now, I don't think it would account for the difference between 0.07 and 0.18, though; not sure about that)

Does anyone know how much faster GPU to 72 allowed us to find this new prime?

I am considering getting a book printed of the decimal expansion of M74207281. It's not a poster, but it's probably the next best thing. lightningsource.com (the only publisher I found that supports books over 800 pages) gives a quote of $29.54 USD (plus shipping) for a 1200 page hardcover. I haven't looked past their quote calculator, so I'm not sure if they would be too happy about printing a book like this with no author or words and at a smaller font size (at most 5.5).

[QUOTE=Jayder;423172]I am considering getting a book printed of the decimal expansion of M74207281. It's not a poster, but it's probably the next best thing. lightningsource.com (the only publisher I found that supports books over 800 pages) gives a quote of $29.54 USD (plus shipping) for a 1200 page hardcover. I haven't looked past their quote calculator, so I'm not sure if they would be too happy about printing a book like this with no author or words and at a smaller font size (at most 5.5).[/QUOTE]You could make it cheaper by not printing the middle 95% of the pages, just leave them blank. Considering that people will only look at the start and the end digits they will never notice that the middle pages are all blank. :razz:

[URL="http://www.sentryreviews.com/business/2234-million-jobs-scientists-find-new-record-prime-number-7196.html"]Auto translated?[/URL]
:rofl:

[QUOTE=axn;423175][URL="http://www.sentryreviews.com/business/2234-million-jobs-scientists-find-new-record-prime-number-7196.html"]Auto translated?[/URL]
:rofl:[/QUOTE]
Haha, Emmett Brown? Looks more like Emelius Browne..

[QUOTE=ixfd64;423170]Does anyone know how much faster GPU to 72 allowed us to find this new prime?[/QUOTE]

It looks like it was TFed to 75 bits, not sure how much was via GPUto72 though. Chris should be able to tell us.
[url]http://www.mersenne.ca/exponent.php?exponentdetails=74207281[/url]

[QUOTE=0PolarBearsHere;423121]It's currently in the slashdot firehose as red, so it might be hitting the front page soon.[/QUOTE]

Now on the front page of slashdot
[url]http://science.slashdot.org/story/16/01/20/0137259/new-mersenne-prime-discovered-largest-known-prime-number-274207281---1[/url]

[QUOTE=ewmayer;423144]I use my own code to generate the decimal printouts - still way slower than it could be, took ~3 hours on 1 cpu of my 2GHz Core2Duo macbook classic, probably at least 100x slower than it could be[/QUOTE]

Piping the output of this into a file took 6 sec:

[CODE]#include <gmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <math.h>

void main()
{
mpz_t s;
mpz_init_set_ui(s,0);
mpz_ui_pow_ui(s,2,74207281); mpz_sub_ui(s,s,1);
gmp_printf("%Zd",s);
}[/CODE]

[QUOTE=ATH;423188]Piping the output of this into a file took 6 sec:
[/QUOTE]

5->7 minutes to get the right libraries compiled and installed, 5 minutes to fix an error in my command line, 4.5 seconds to run the code haha (followed by a few minutes to download the zip file from the server, extract it, and strip the white space to do a diff).