What is Prime95 ?
 

^^^^^^^^^^^, the question is in the topic :)

http://www.mersenne.org/

Its a piece of software to test for Mersenne Prime numbers.

thanks, but what do i benefit from using it.

Prime95 is one of the primary benchmark programs in the world today.

It is universally accepted in the hardware world that if a computer cannot successfully run the torture test in Prime95, that computer has something wrong with it.

You can win $100,000, split with the project, by finding a 10,000,000 digit mersenne prime (your share will be approximately $50,000.

You can win $5,000 by finding the next largest mersenne prime.

You can factor and do lucas-lehmer tests on large mersenne numbers in several different ways.

Some people like to garden, some like to determine the next biggest prime number in the world. So part of it is preference, call it a hobby. Some of us can't stand to let CPU cycles go idle, so this is, in my opinion, the best way to push your CPU/memory to the maximum limit *and* be able to use your PC for normal stuff at the same time.

[quote="os008"]thanks, but what do i benefit from using it.[/quote]
If you like recreational mathematics, Prime95 is a great way to participate in that.

If you are the type of person who likes to buy lottery tickets, then you might be attracted by the small chance that you could win several thousand dollars by using Prime95.

If you have a desire to be famous (primarily among mathematicians, that is :), Prime95 might enable you to be forever known as a co-discoverer of a Mersenne prime, one of the jewels of mathematics.

so what do i have to do to discover this number ?, i have started the program and it has done a self test after communicating with the server, then it just continued somethings which i don't understand.

[quote="os008"]so what do i have to do to discover this number ?, i have started the program and it has done a self test after communicating with the server, then it just continued somethings which i don't understand.[/quote]

When you start the program for the first time, it will always do a selftest to see if your computer is working properly. If it does, it will contact the server and asks for a number to test.

It first checks if the number has no small factor by trying to divide the number to test by [i]small[/i] primes. This is called trail factoring. A lot of numbers have already been sufficientely trailfactored by others, so it will probably skip this stage.

After that the program checks if P-1 has already been done. P-1 is a special algorithem which might find larger factors of the number. If no P-1 has been done, the program will start running it.

P-1 consists of 2 stages, the length of the second stage depends on how much memory you give it. The more memory, the higher the chance you'll find a factor.

After both P-1 stages are done, the program will perform a Lucas Lehmer test. This is a test that determines if the number you're testing is prime. Only after this test is 100% complete it can be determined if the number you are testing is prime.

Take a look at the [url=http://www.mersenne.org/math.htm]math[/url] page for more information.

So a screen output could look like this. (This computer runs Linux so I can get the screen output to a file.)

P-1:[quote][size=9]Starting P-1 factoring on M17835847 with B1=225000, B2=5625000
Chance of finding a factor is an estimated 5.69%
P-1 on M17835847 with B1=225000, B2=5625000
[Jul 6 19:06] M17835847 stage 1 is 15.39% complete. Time: 2031.267 sec.
[Jul 6 19:40] M17835847 stage 1 is 30.79% complete. Time: 2030.531 sec.
[Jul 6 20:14] M17835847 stage 1 is 46.19% complete. Time: 2030.394 sec.
[Jul 6 20:47] M17835847 stage 1 is 61.59% complete. Time: 2030.375 sec.
[Jul 6 21:21] M17835847 stage 1 is 76.99% complete. Time: 2030.101 sec.
[Jul 6 21:55] M17835847 stage 1 is 92.39% complete. Time: 2030.272 sec.
M17835847 stage 1 complete. 649364 transforms. Time: 13183.308 sec.
Starting stage 1 GCD - please be patient.
Stage 1 GCD complete. Time: 118.536 sec.
[Jul 6 23:09] M17835847 stage 2 is 15.13% complete. Time: 3291.571 sec.
[Jul 7 00:03] M17835847 stage 2 is 30.26% complete. Time: 3282.908 sec.
[Jul 7 00:58] M17835847 stage 2 is 45.50% complete. Time: 3295.917 sec.
[Jul 7 01:53] M17835847 stage 2 is 60.63% complete. Time: 3285.726 sec.
[Jul 7 02:48] M17835847 stage 2 is 75.86% complete. Time: 3291.600 sec.
[Jul 7 03:43] M17835847 stage 2 is 90.98% complete. Time: 3287.807 sec.
M17835847 stage 2 complete. 658644 transforms. Time: 21692.985 sec.
Starting stage 2 GCD - please be patient.
Stage 2 GCD complete. Time: 114.474 sec.
Contacting PrimeNet Server.
Sending text message to server:
UID: patrik/zeta, M17835847 completed P-1, B1=225000, B2=5625000, WZ2: CD34F248
Sending result to server for exponent 17835847
Done communicating with server.
[/size][/quote]
Then the Lucas-Lehmer test starts. (This normally starts right after the P-1 test. But I did the LL test for another exponent in between, by setting SequentialWorkToDo=0 in prime.ini.)[quote][size=9]Starting primality test of M17835847
[Jul 19 08:20] Iteration: 50000 / 17835847 [0.28%]. Per iteration time: 0.041 sec.
[Jul 19 08:54] Iteration: 100000 / 17835847 [0.56%]. Per iteration time: 0.041 sec.
[Jul 19 09:27] Iteration: 150000 / 17835847 [0.84%]. Per iteration time: 0.041 sec.
[Jul 19 10:02] Iteration: 200000 / 17835847 [1.12%]. Per iteration time: 0.041 sec.
[Jul 19 10:35] Iteration: 250000 / 17835847 [1.40%]. Per iteration time: 0.041 sec.

[---]

[Aug 1 04:47] Iteration: 17600000 / 17835847 [98.67%]. Per iteration time: 0.041 sec.
[Aug 1 05:20] Iteration: 17650000 / 17835847 [98.95%]. Per iteration time: 0.041 sec.
[Aug 1 05:54] Iteration: 17700000 / 17835847 [99.23%]. Per iteration time: 0.041 sec.
[Aug 1 06:28] Iteration: 17750000 / 17835847 [99.51%]. Per iteration time: 0.041 sec.
[Aug 1 07:02] Iteration: 17800000 / 17835847 [99.79%]. Per iteration time: 0.041 sec.
M17835847 is not prime. Res64: [i](a hexadecimal number)[/i]. WZ2: 953169F1,3065399,00000000
Contacting PrimeNet Server.
Sending result to server for exponent 17835847
Sending text message to server:
UID: patrik/zeta, M17835847 is not prime. Res64: [i](a hexadecimal number)[/i]. WZ2: 953169F1,3065399,00000000
Done communicating with server.
[/size][/quote]
The computer is a P4 running at 2572 MHz.

[quote="os008"]so what do i have to do to discover this number ?[/quote]
Now that smh and patrik have given details, I'll just provide the short answer: Be patient for a few weeks.

Sit back. Relax. Browse through the rest of this forum. :)

thanks guys very much for the explanation ... then did anyone discover this prime number they r all searching for (what is it in the first place), i'm in the faculty of engineering department of aerospace .. so i should understand what this program is doing or what's its purpose ! but i can't .. if u could give me the program bigger purpose in short and what is that prime number i'll be very thankful