20160222, 16:52  #1 
"Daniel Jackson"
May 2011
14285714285714285714
673 Posts 
Mersenne.ca bug...
Look at the factorbounds graphs at the bottom:
http://www.mersenne.ca/exponent/74207321 If you point to the red circle (which represents the 1 known factor), it shows a negative number, which, if you add to the known prime factor, you get 2^{64}. Is this a problem with 64bit signed integers? 
20160531, 02:26  #2 
Romulan Interpreter
Jun 2011
Thailand
2^{4}×13×47 Posts 
Sorry for waking this up, I didn't know where to post, not that I would care much about the well ordered topics on the forum but I know James is a busy guy and he only read very few topics here around.
So, there is a small cosmetic bug on mersenne.ca site: The http://www.mersenne.ca/exponent/57885161 would need a small manual tweak, it does not show the triple arrow going right. I think the pointers were added by hand (blearh! ) and they are not "computed" by reading the exponents DB. So, the news of the fact that we discovered a new prime escaped to the parsing guy there, hehe. And because we are here, the dots designating "uncertain" mersenne primes in the table at http://www.mersenne.org/primes/ won't stay purple, but appear blue and change back to blue when you navigate in the table. I would like them to remain purple (or violet, whatever that color is). 
20160531, 02:56  #3 
Romulan Interpreter
Jun 2011
Thailand
2^{4}×13×47 Posts 
The Hidden Mersenne Prime
Nice title for a book. For a new subforum too.. But let's stay inside of this topic for now. Anyhow, this worth a new post. Related to the former one, but more interesting. I continued to play with those arrows and guess what I found:
I know how to find new mersenne primes. Proven formula! All I have to do is to take a table of prime numbers, then James' site, start from a prime, any prime, and click the arrows in the table. Any arrow, left or right, in any numbers. And follow close with the numbers in the table, watch them tight. If any prime is skipped, i.e. I have it in the table, but the arrow jumps over it, then it is a high probability I found a new prime: Example: M74207281. You fill any exponent in James' site, a bit lower than this (and click any right arrows) or a bit higher than this (and click left arrows), then the number is skipped, the form can't find any prime between 74207279 and 74207297, no matter what arrows you click. But if you fill 74207281 exactly, it shows you that is prime. For sure I have to do this procedure with exponents over 332M, watch which one is skipped, and I will find a new mersenne prime. It takes much shorter than a LL test... 
20160531, 03:48  #4  
Jan 2010
2×3×19 Posts 
Quote:
{What arrows?} 

20160531, 04:47  #5  
Romulan Interpreter
Jun 2011
Thailand
2^{4}·13·47 Posts 
Click the second link in my post, scroll down. Hover the mouse over the big blue dots in the graph. Then hover the mouse over the table, while the graph is still visible. Repeat...
Quote:
Click the first link in my post. Please navigate to former mersenne prime, by clicking the tripplearrow pointing left. Repeat, to see other mersenne primes. Try in the opposite direction. When you reach back the starting point, click the triple arrow pointing right, to go to the next mersenne prime... "Which arrow??". Related my second post, click on http://www.mersenne.ca/exponent/74207281. Yeah, voila! is prime. Click any arrows you like there on the right of the exponent. Try to find it back, using the arrows. Told you so! License agreement (EULA): by reading this post, you agree to the fact that you are not allowed to use my algorithm to find new mersenne primes, as I described it in my second post. Edit: I just sent a PM to James, I am sure he didn't see this topic (including the first message from Stargate) and he will take care of the issues as fast as his time allows, as usual. Last fiddled with by LaurV on 20160531 at 04:58 

20160531, 12:47  #6  
"James Heinrich"
May 2004
exNorthern Ontario
3500_{10} Posts 
I don't generally browse the forum, I usually only see stuff in a handful of subscribed threads (until LaurV bothers me with PMs ). Please post any mersenne.ca related bugs in the mersenne.ca thread.
Quote:
PHP is very good at automagically typecasting variables as needed. Unfortunately it sometimes gets it wrong and it's hard to override. In this case, the factor is stores as a string, and used as a string, but in one place it's used as a string array key. But... for small factors it looks like an integer so PHP uses it as an integer array key instead of a string key, and in that context it gets cast as a negative number when in the bitrange just below PHP_INT_MAX (either 2^{31}2^{32} or 2^{63}2^{64}). I gave the code a severe talkingto and told it not to do that again. I also had to prepend a nonnumeric character to the array key to force it to always handle it as a string. Quote:
Quote:
I thought we were talking about mersenne.ca bugs here, but I have fixed that for you anyways Well of course. The arrow buttons are generated for next exponent with/without factors that are not prime. So I have to query the list of Mersenne primes (I have the full list up to M(2^{32}) of course) and skip those ones. 

20160601, 01:58  #7 
Romulan Interpreter
Jun 2011
Thailand
2^{4}×13×47 Posts 
Stargate's bug does not seem to be fixed, still shows the negative number. Additionally, now it shows a "NaN" instead of the number of bits for the factor. This is in tooltip when you hover over the big dot in the factors table.
The violet dots in the primes graph of PrimeNet is fixed  it looks very good now! The arrow links are not fixed. They work well up to M48, but the trippleright of M48 is still not showing, and also for the next prime exponent after the M48. It starts appearing again after the second next prime exponent after M48, when you can click it and go to M49. Around M49, forward navigation is ok, backward navigation still skips M49. Thanks a million for your efforts to sort out these small cosmetic things. We really appreciate! Last fiddled with by LaurV on 20160601 at 01:59 Reason: s/on/ok/ 
20160601, 02:26  #8 
"James Heinrich"
May 2004
exNorthern Ontario
DAC_{16} Posts 
I think they are, but you have not sufficiently refreshed your browser. The mersenne.ca exponent pages are quite forcibly cached, so you'll need to CtrlF5 forciblyrefresh your browser to see the new, fixed pages.

20160601, 02:51  #9 
Jan 2010
2·3·19 Posts 
Oh no. The Rapid Prime Finding Feature (RPFF) has been disabled. So we have to use the Leisurely {prime} Locater (LL) instead.
Last fiddled with by vsuite on 20160601 at 02:52 
20160601, 05:07  #10 
Romulan Interpreter
Jun 2011
Thailand
2^{4}·13·47 Posts 
Yeah, you killed my algorithm... Bad James!
{ do I have to hit CtrlF5 to every exponent? it seems so...} {yes, it does that, if I visited the page in the past... hmmm... I just killed all the history for all the pages ending in .ca, and it seems to work very well now} Last fiddled with by LaurV on 20160601 at 05:14 
20190609, 05:40  #11 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
5·953 Posts 
Seems my parm requests are being ignored.
Above the GREEN line is what I entered just before I clicked on "Calculate" on the Left.
Below the GREEN line is the output I got … NOTE: "Use B1/B2 above" was changed to "Save 2LL Tests" It didn't do that a few weeks ago. 
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