20030303, 14:18  #1 
Mar 2003
Yucaipa, CA, USA
8_{10} Posts 
How long does factoring run on 2^33,xxx,xxx type numbers?
Hi,
I'm running my first 2^33M1 number and my machine has been factoring for 2 days now. It is a 2.5GHz, 1Gbyte DRAM machine. Does this sound reasonable? Thank you! Nick 
20030303, 14:36  #2 
Oct 2002
Lost in the hills of Iowa
2^{6}×7 Posts 
It takes about a day for my P4 2.36 Ghz machine to factor a 20,xxx,xxx number  but those only factor to 2^67 depth.
33,xxx,xxx factor to 2^69 depth  so should take 4 days or a little less for your machine. 
20030303, 14:45  #3 
Mar 2003
Yucaipa, CA, USA
1000_{2} Posts 
Thanx Q.
I think it is great we're getting some good factoring in for the Number Theory guys and gals. Nuke 
20030303, 15:44  #4 
Dec 2002
Frederick County, MD
2·5·37 Posts 
I recently factored a 2^333xxxxx1 number to 2^68, and it took 42 hours running non stop with nothing else running on a P4 2.4Ghz. I think you would actually have to have an exponent greater than 3510000 to have Prime95 automatically trial factor to 2^69. I'm not sure, but I think the number I was working on had been previously TFed to 2^60.

20030303, 16:16  #5  
P90 years forever!
Aug 2002
Yeehaw, FL
2^{2}·3·641 Posts 
Re: How long does factoring run on 2^33,xxx,xxx type numbers
Quote:


20030303, 17:31  #6 
Mar 2003
Yucaipa, CA, USA
1000_{2} Posts 
I don't mind running the factoring software a little longer than "Standard P95" is there soemhting I can put in the .int file to give it the OK to look a little further?
Is how much time longer would I consume, for example, if I checked just one more bit. Also, would I lose the work I've done up 'till now. 
20030303, 18:56  #7 
"Sander"
Oct 2002
52.345322,5.52471
10010100101_{2} Posts 
Factoring 1 bit deeper means you are factoring twice as far, so this takes at least double so long.

20030303, 19:08  #8 
Aug 2002
F9_{16} Posts 
And a lot longer than twice in the case of going past certain numbers of bits, 62 and more so 65 come to mind.
Is the machine a P4 or an XP? The XP tends to factor pretty fast. 
20030306, 10:42  #9 
"GIMFS"
Sep 2002
Oeiras, Portugal
10111101001_{2} Posts 
nukemyrman wrote:
I don't mind running the factoring software a little longer than "Standard P95"... Don´t use a P4 for that! P4s perform like crap on Trial Factoring, so stick to the minimum TF defined by the client, and use the power of the SSE2 instruction set for LL. From some data I have collected, I assure you it is a waste to engage P4s on long factoring assignments. 
20030306, 13:29  #10 
Dec 2002
Frederick County, MD
2×5×37 Posts 
Trial Factoring over 2^64
I don't remember where I saw it, but I thought I saw somewhere that the P4 does really good with TFing once you get past 2^64, since than you have more than 64 bits. Is this true?

20030306, 13:35  #11 
"GIMFS"
Sep 2002
Oeiras, Portugal
10111101001_{2} Posts 
Shortly after having posted my advice to nukemyrman, I realized we were in fact talking about TFing beyond 2^64. For those ranges, the SSE2 instructions are used, so I think P4s do indeed a lot better than up to 2^63. I don´t have figures for those ranges, but I will at least give P4s the benefit of doubt... :)

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