Go Back > Great Internet Mersenne Prime Search > Software

Thread Tools
Old 2019-07-18, 02:58   #1
wfgarnett3's Avatar
"William Garnett III"
Oct 2002
Langhorne, PA

2×43 Posts
Default Prime95/PrimeNet Mersenne Probability bug


I have the screenshots for you to explain this bug.

I got a new assignment and my worktodo.txt file is timestamped 7/17/2019 12:57AM when it got the assignment and has the below line (note the worktodo.txt file has not changed at all and is timestamped the same still to this moment)

[Worker #1]

At 10:39PM on 7/17 in Prime95 I went Test-->Status and it as shown in the attached screenshot1.png "The chance that the exponent you are testing will yield a Mersenne prime is about 1 in 662132".

I went Help -->About PrimeNet Service to send the 5 million residue.
I then exited Prime95.

I went back into Prime95 and went Test-->Status and now it states as shown in the attached screenshot2.png "The chance that the exponent you are testing will yield a Mersenne rpme is about 1 in 1601932".

That is the bug -- I am testing the same exponent, worktodo.txt did not get touched at all, yet a couple minutes apart Prime95/PrimeNet now reports a different probability. For the rest of the time I test this exponent it will report the different probabilty.

This happened for me for exponents in this new Prime95 (29.8 build 3) when I do my PRP first time tests -- it changes the probability and for the rest of the test until it is done will continue to report this incorrect probability. The previous 29.4 software I used for LL first time tests never did this -- it would always report the 1 in 662132 probability for instance.

Can you advise what is happening?

Attached Thumbnails
Click image for larger version

Name:	screenshot1.png
Views:	130
Size:	128.5 KB
ID:	20779   Click image for larger version

Name:	screenshot2.png
Views:	131
Size:	87.8 KB
ID:	20780  
wfgarnett3 is offline   Reply With Quote
Old 2019-07-18, 04:27   #2
Romulan Interpreter
LaurV's Avatar
"name field"
Jun 2011

1024510 Posts

No idea if you found a bug or not (never looked for these probability numbers, they have no practical use, we just know from experience that the probability to find a prime is quite small )

But... The probabilities can change on the fly if somebody reports more TF or some P-1 with larger bounds (not the case here, tho).

Also... This exponent had a P-1 of about 5% and it was TF to 76 bits, therefore the probability of LL turning it prime is something like 1 in over a million. I think the first number is the one which is wrong, and the last one is the correct one. But this is just "in the head" approximation, I didn't take the pencil, so I could be wrong.

Edit: mind that your worktodo does not contain information of how far factored, and pm1 bounds, etc, those are only known after contacting the server. A typical LL line look like: "Test=blahblahkeykey,332199017,79,1", which for example, tells me the TF level, and give a hint about P-1. But for PRP, you need to contact the server to know these things. So, from this point of view, it also makes sense that the second number is right.

The chance of your number to be prime does not depend on the PRP or LL, it depends mostly of the exponent size and how much work was already done on it, except the PRP or LL work you are currently doing. Progressing into the LL or PRP test does not change the chances of the number being prime.

Therefore don't be so sad, your chances to find a prime it is just very-very-very small

Last fiddled with by LaurV on 2019-07-18 at 04:42
LaurV is offline   Reply With Quote
Old 2019-07-18, 21:11   #3
Bemusing Prompter
ixfd64's Avatar
Dec 2002

1001101101112 Posts

I believe this is fixed in version 29.8 build 5:
ixfd64 is offline   Reply With Quote
Old 2019-07-19, 03:37   #4
wfgarnett3's Avatar
"William Garnett III"
Oct 2002
Langhorne, PA

5616 Posts

Thanks ixfd64 I see George states it is fixed in the later version

21) For PRP work, TF depth was not being written to worktodo.txt unless P-1 was required. This caused Test/Status to underestimate the chance that the PRP test would find a new Mersenne prime. Fixed in 29.8 build 5
wfgarnett3 is offline   Reply With Quote

Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Primenet result not propagandizing to Gordon 5 2015-08-29 18:14
I don't get the '' joblack Information & Answers 28 2010-03-24 22:13
Probability of a Mersenne number being prime vimil Information & Answers 13 2007-12-12 11:21 messed up . petrw1 PrimeNet 0 2007-09-07 20:28
probability of finding a Mersenne prime optim Math 2 2003-12-06 19:03

All times are UTC. The time now is 01:24.

Thu Dec 1 01:24:43 UTC 2022 up 104 days, 22:53, 0 users, load averages: 1.14, 1.28, 1.26

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, 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.

≠ ± ∓ ÷ × · − √ ‰ ⊗ ⊕ ⊖ ⊘ ⊙ ≤ ≥ ≦ ≧ ≨ ≩ ≺ ≻ ≼ ≽ ⊏ ⊐ ⊑ ⊒ ² ³ °
∠ ∟ ° ≅ ~ ‖ ⟂ ⫛
≡ ≜ ≈ ∝ ∞ ≪ ≫ ⌊⌋ ⌈⌉ ∘ ∏ ∐ ∑ ∧ ∨ ∩ ∪ ⨀ ⊕ ⊗ 𝖕 𝖖 𝖗 ⊲ ⊳
∅ ∖ ∁ ↦ ↣ ∩ ∪ ⊆ ⊂ ⊄ ⊊ ⊇ ⊃ ⊅ ⊋ ⊖ ∈ ∉ ∋ ∌ ℕ ℤ ℚ ℝ ℂ ℵ ℶ ℷ ℸ 𝓟
¬ ∨ ∧ ⊕ → ← ⇒ ⇐ ⇔ ∀ ∃ ∄ ∴ ∵ ⊤ ⊥ ⊢ ⊨ ⫤ ⊣ … ⋯ ⋮ ⋰ ⋱
∫ ∬ ∭ ∮ ∯ ∰ ∇ ∆ δ ∂ ℱ ℒ ℓ
𝛢𝛼 𝛣𝛽 𝛤𝛾 𝛥𝛿 𝛦𝜀𝜖 𝛧𝜁 𝛨𝜂 𝛩𝜃𝜗 𝛪𝜄 𝛫𝜅 𝛬𝜆 𝛭𝜇 𝛮𝜈 𝛯𝜉 𝛰𝜊 𝛱𝜋 𝛲𝜌 𝛴𝜎𝜍 𝛵𝜏 𝛶𝜐 𝛷𝜙𝜑 𝛸𝜒 𝛹𝜓 𝛺𝜔