20190913, 23:21  #1497 
Undefined
"The unspeakable one"
Jun 2006
My evil lair
13·409 Posts 

20190915, 23:43  #1498 
Sep 2002
756_{10} Posts 
P1 found a factor in stage #2, B1=885000, B2=18585000.
UID: Jwb52z/Clay, M96078113 has a factor: 40150180980878122799159 (P1, B1=885000, B2=18585000) 75.088 bits. 
20190917, 18:28  #1499 
Sep 2002
2^{2}·3^{3}·7 Posts 
P1 found a factor in stage #1, B1=820000.
UID: Jwb52z/Clay, M94654033 has a factor: 7507521220789479758248769 (P1, B1=820000) 82.635 bits. 
20190925, 00:38  #1500 
"mrh"
Oct 2018
Temecula, ca
5·11 Posts 
Found one for 7111127  786612060695816024641268553407 99.312 bits

20190929, 04:28  #1501 
Sep 2002
1364_{8} Posts 
P1 found a factor in stage #1, B1=890000.
UID: Jwb52z/Clay, M96570209 has a factor: 24529069813789561422559319 (P1, B1=890000) 84.343 bits. 
20190929, 21:07  #1502 
"mrh"
Oct 2018
Temecula, ca
5×11 Posts 
I think this is the largest I've found so far 3333397 5987402934250702953071699518972409 112.206 bits

20190929, 21:12  #1503  
"James Heinrich"
May 2004
exNorthern Ontario
B0A_{16} Posts 
Quote:
Last fiddled with by James Heinrich on 20190929 at 21:12 

20191003, 22:00  #1504 
Nov 2018
Poland
2·7 Posts 
Hey, I read that GPUs are more efficient on higher bitlevels. So why is there less GHzdays / day in 7374 than in 7173?
Code:
no factor for M909985499 from 2^71 to 2^72 [mfakto 0.14Win cl_barrett15_73_gs_2] tf(): total time spent: 1m 9.138s (656.78 GHzdays / day) no factor for M909985499 from 2^72 to 2^73 [mfakto 0.14Win cl_barrett15_73_gs_2] tf(): total time spent: 2m 17.558s (660.21 GHzdays / day) no factor for M909985499 from 2^73 to 2^74 [mfakto 0.14Win cl_barrett15_82_gs_2] tf(): total time spent: 5m 6.655s (592.31 GHzdays / day) no factor for M909985451 from 2^71 to 2^72 [mfakto 0.14Win cl_barrett15_73_gs_2] tf(): total time spent: 1m 8.872s (659.32 GHzdays / day) no factor for M909985451 from 2^72 to 2^73 [mfakto 0.14Win cl_barrett15_73_gs_2] tf(): total time spent: 2m 17.148s (662.19 GHzdays / day) no factor for M909985451 from 2^73 to 2^74 [mfakto 0.14Win cl_barrett15_82_gs_2] tf(): total time spent: 5m 5.676s (594.21 GHzdays / day) 
20191004, 00:11  #1505  
"Sam Laur"
Dec 2018
Turku, Finland
2^{2}·7·11 Posts 
Quote:
Longer answer: Instead of division, mfakto (and mfaktc) use Barrett reduction, that basically turns division into multiplication, and because of the relatively small multipliers available in the GPU cores, there are some tricks that need to be done to extend the precision. There are some further optimization tricks that can be done, but these have the side effect of eating into this extended precision, so each more optimized GPU kernel has a lower corresponding maximum bitlevel. The GHzday formula doesn't take these changes into account, as it is supposed to be related to the time a CPU takes to factor something to a given bitlevel, not a GPU. Now, I'm not familiar with AMD or mfakto specifics, are the barrett15_* kernels really still more efficient than barrett32_* even on more modern cards? 

20191004, 03:41  #1506  
Romulan Interpreter
Jun 2011
Thailand
31·271 Posts 
Quote:
Correct answer: (which correctly implies that my previous answer, as well as both answers from the anteposter are wrong ) : Because the formula to calculate the credits is wrong, in the sense that it is only an approximation, based on empirical evidence, derived from middle age times when only the CPUs could do TF. The GHzDays/Day (as a measuring unit) should be the amount of work that a singlecore 32 bits CPU can do in one day, running at 1 GHz. This is (approx) how it was defined long ago. This should have nothing to do with the exponents, bitlevels, TF, LL, whatever. But invention of multicores, 64bit CPUs, GPUs, airplanes, flying spaghetti monster, and other alien stuff which invaded us in the last time, heavily changed the odds, and anyhow, such measurement, even if we could make it extremely accurate, would not be useful (think about it! if your card will always show 562.73 GHzD/D regardless of what you are doing with it, what should be the point?). Actual calculus could be altered by many things, including a "stimulation" for people to do certain type of work (yes, you may get more credit doing this or that bitlevel, in this or that range, because that is most needed now  well, dream on! that would be ideally, wouldn't be?) Of course, everybody can use his/her cards and electricity money to do whatever type of work fits them better. Last fiddled with by LaurV on 20191004 at 03:46 

20191004, 08:38  #1507 
"James Heinrich"
May 2004
exNorthern Ontario
5412_{8} Posts 
GHzdays credit for TF is broadly based on bitlevel, derived from how well an Intel CPU of decades ago could process TF work using Prime95 (example). The credit is scaled according to 3 ranges: up to 62bit is "easy" and given 62.58% credit, 6364 bit is "slightly easier" and given 95.15% credit, and >=65bit gets 100% credit.
Since all the TF done now is >65bit the credit given is linear, but is subject to architectural efficiencies of the GPU (or whatever device you're using) and the software running the calculation. Broadly speaking, higher bit depths require more bits to be played with at once and therefore slow the calculations down somewhat, which is why mfaktx will choose the smallest kernel that can process the current assignment, since that will be the fastest. For historical interest, for the oldtimers, I found these old notes in the code: Code:
CPU credit  background information: In Primenet v4 we used a 90 MHz Pentium CPU as the benchmark machine for calculating CPU credit. The official unit of measure became the P90 CPU year. In 2007, not many people own a plain Pentium CPU, so we adopted a new benchmark machine  a single core of a 2.4 GHz Core 2 Duo. Our official unit of measure became the C2GHD (Core 2 GHz Day). That is, the amount of work produced by the single core of a hypothetical 1 GHz Core 2 Duo machine. A 2.4 GHz should be able to produce 4.8 C2GHD per day. To compare P90 CPU years to C2GHDs, we need to factor in both the the raw speed improvements of modern chips and the architectural improvements of modern chips. Examining prime95 version 24.14 benchmarks for 640K to 2048K FFTs from a P100, PII400, P42000, and a C2D2400 and compensating for speed differences, we get the following architectural multipliers: One core of a C2D = 1.68 P4. A P4 = 3.44 PIIs A PII = 1.12 Pentium Thus, a P90 CPU year = 365 days * 1 C2GHD * (90MHz / 1000MHz) / 1.68 / 3.44 / 1.12 = 5.075 C2GHDs 
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