20071018, 05:44  #1 
May 2007
Kansas; USA
10,597 Posts 
Top5 prime quadruplet found
Another set of archivable primes for RPS. Found: the 4th highest prime quadruplet of all time! Here it is:
477707955423*2^38021, +1, +5, and +7 It is the #1 largest prime quadruplet ever found that contains a Riesel and Proth prime! (+5 and +7 primes proven with Primo after LLR found them as probable primes.) Gary 
20071018, 07:13  #2 
"Curtis"
Feb 2005
Riverside, CA
1429_{16} Posts 
How long does Primo take to prove a number that size prime? What version of Primo do you have?
Curtis 
20071018, 18:09  #3  
May 2007
Kansas; USA
10597_{10} Posts 
Primo
Quote:
It took 1 hour, 3 minutes for the +5 candidate and 1 hour, 21 minutes for the +7 candidate. I'm not sure why the difference. Nothing else was running on my machine either time. It probably has something to do with how well it could factor the number 1 greater and/or 1 less than each number. Of course LLR found them to be PRP in about 1/20th of a second. This is a reduced form of 1910831821692*2^38001/+1/+5/+7. I had sieved n=3800 for k<=6T including all even candidates. A whole bunch of 'really big' files! On another note, I got an Email from Prof. Caldwell. I needed to create a new proof code that includes Primo for the +5 and +7 candidates. I've now done that and he is going to 'move them over'. I wanted to credit LLR solely since it was 99.9% of the total primefinding time but that doesn't work for PRP's at the top5000 site. I guess since it didn't prove them prime and whatever software proves them prime is what gets credit. So LLR will get credit for 1 and +1 and Primo for +5 and +7. Gary 

20071026, 06:21  #4 
May 2007
Kansas; USA
10,597 Posts 
Another top 5 quad found!
I decided to finish up my sieved range of k=16T for n=3800 looking for quads. With barely better than a 1 in 4 chance of finding another with the sieved range left, the prime Gods were on my side and it kicked out another one! Here it is:
2722420456827*2^38001, +1, +5, +7 This one is now the 4th largest and the prior one is 5th. Together they are the top 2 quads ever to contain Riesel and Proth primes. Curtis, for some reason, Primo runs faster on an Athlon than on a core2duo. This one only took 40 and 44 mins. respectively to prove the +5 and +7 primes. Checking the prior one on the Athlon, it took 42 and 50 mins. respectively vs. over an hour each on the core2duo. I tested each one at a time on both machines with the other core running something else in both cases. Very strange! Gary 
20071026, 08:45  #5  
Sep 2004
2·5·283 Posts 
Quote:
Can you set Primo's affinity instead of letting the OS choose it automatically? Try going to task manager and set core 0 to Primo and core 1 to the other thing you're running, then see what happens.... Carlos Last fiddled with by em99010pepe on 20071026 at 08:46 

20071026, 09:11  #6 
Nov 2003
3622_{10} Posts 
It is well known that Primo is much faster of Athlons and Opterons because it's based on integer computation which is much faster on AMD cpu's. Pentiums are much faster for floating point numbers. I found that my old Athlon2000, cpu clock 1.66G is just a little bit faster than (2 year old) 3.6G Pentium Xeon.

20071026, 15:31  #7  
May 2007
Kansas; USA
10597_{10} Posts 
Quote:
Carlos, I had LLR going on one core (on another effort) and Primo on the other when I tested Primo on both the Core2duo and dualcore Athlon. Since both are 2core machines, I'm thinking having a separate affinity would have made little difference. Let me know if you think otherwise. Hum...I'm not familiar with how to change the core in the task manager. I'll have to look into that. Primo doesn't seem to have a way to change the affinity. Gary Last fiddled with by gd_barnes on 20071026 at 15:39 

20071026, 16:11  #8 
May 2005
2^{2}×11×37 Posts 

20071026, 16:17  #9 
May 2007
Kansas; USA
10,597 Posts 
OK, thanks. I see that now. Duh!
Question for anyone here...on a dualcore machine, is there any benefit to having one instance of LLR run on CPU 0 and the other on CPU 1 instead of the default of letting them both run on both CPUs? I always just let both instances default to running on both CPUs. Thanks, Gary 
20071026, 22:46  #10 
"Dave"
Sep 2005
UK
AD8_{16} Posts 
Gary,
If you look at Task Manager  Performance you should see that the two instances will fight each other if you do not set the affinity of each. The symptom is that that each instance does not always show 100% CPU usage. The net result is that you lose some processing power for each instance. I always set the affinity either using the program itself or using a program that I wrote that allows you to set the affinity of any given program under Windows. Alternatively you can manually set the affinity as described by Carlos. 
20071027, 01:54  #11  
May 2007
Kansas; USA
10,597 Posts 
Quote:
Excellent! Thanks a bunch. I'll change all of my dualcore machines now to have separate affinities for each instance of LLR, srsieve, or newpgen. Gary 

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