Quote from: Puycheval on March 10, 2014, 09:47:07 PM

Quote from: Halofire on March 10, 2014, 09:08:06 PM

We need to know how n-factor affected cpu miners, if hashes halved. Is anyone even cpu mining?

I don't know for ultracoin but this is what was tested for Yacoin when it was cpu only. You can see hashrate is roughly halved with each N increase as long as it doesn't change of memory type. For example, the change 13->14 shows a big loss because dataset doesn't fit in L2 cache anymore.

Code:

Nfactor N Memory UNIX Time Date/Time in GMT Hashrate for 2x Xeon E5450
13 16384 2MB 1380574112 Mon - 30 Sep 2013 - 20:48:32 GMT 2,276
14 32768 4MB 1384768416 Mon - 18 Nov 2013 - 09:53:36 GMT 606

Quote from: Protagonus on March 10, 2014, 09:57:55 PM

I see there are some questions that keep popping up again and again. Might as well pop in to see if I can help in some way.

Quote from: dbappa on March 10, 2014, 04:06:31 PM

At what point does it become pointless to use our GPUs?

If the current n-factor gives me 120/150 KH/s for my 280Xs/290, the next will be be 60/75 and then 30/38. I will still be able to mine the same number of coins with these hash rates? Just trying to figure out how long my 4 280Xs and one 290 have got with this coin/scrypt.

N = 14 07 / 12 / 14 @ 04:20:16am UTC At this N and beyond it will be more cost effective to mine with CPU.

Quote from: Halofire on March 10, 2014, 07:50:16 PM

Quote from: fredeq on March 10, 2014, 06:14:07 PM

Quote from: Halofire on March 10, 2014, 06:01:57 PM

I would like to know why does n-factor not affect cpu's. yeah yeah memory intensive, multiple threads, ram. i got all that, but if hashrate halves for cpu's as well, which I don't know if it halves, then wouldn't cpu mining still get harder over time as n-factors increase?

Can someone who has been cpu-mining AND experienced any n-factor change answer?

Been wondering this since day 1. Defo needs an answer.

bump

Both CPU and GPU are affected similar, in terms of dropping hash rate each N increase. However, the gap in actual hashrate gets smaller with higher N. As well, CPU's actually "fall-off" slower in hash slightly than gpu / perform better later.
For example 600khs GPU with N increase may be similar to; 600>290>130>60>25>10>5.
Comparing this to a CPU over same N increases; 125> 65> 35> 20> 10>5>2.5

Part of this reason was described best and quoted here;

"CPU's still have a number of advantages over GPU's and ASIC's. They come with double precision floating point hardware, employ very advanced branch prediction mechanisms, incorporate at least 2MB of on chip L2/L3 cache, and are able to speculate through 4-6 branches even in ten year old machines. GPU's can manage 2-5x better double precision floating point performance than a typical CPU, but in some benchmarks, they cannot even manage even speed. The problem is worse for ASIC's, which must be custom designed around a specialized pipeline. "

Again quoting another location; here is a representation of hash rate on a CPU vs increasing N values.

Running 1500 scrypt hashes with N=2048 - 0.00109417 avg. sec per hash
Running 1500 scrypt hashes with N=4096 - 0.00216536 avg. sec per hash
Running 1500 scrypt hashes with N=8192 - 0.00450547 avg. sec per hash
Running 1500 scrypt hashes with N=16384 - 0.00928228 avg. sec per hash
Running 1500 scrypt hashes with N=32768 - 0.01895874 avg. sec per hash
Running 1500 scrypt hashes with N=65536 - 0.04028997 avg. sec per hash
Running 1500 scrypt hashes with N=131072 - 0.08082690 avg. sec per hash

test written in python on an i5-4250U CPU @ 1.30GHz,

In the end it's not that CPU's hash way faster than GPU's at high N's; specifically, it's that CPU's cost less Watts per Kh/s to mine at higher N's.

Some examples of hash rates and setups with CPU's and GPUs @ N = 14; can be seen here - http://yacoinwiki.tk/index.php/Mining_Hardware_Comparison

You can see, as an example here @ N14

2x E5645 Procesors 2x 80W -- 1.53Kh/s

7950 GPU (250w) 1.3-1.5 Kh/s

As shown above. the Processors will give approximately the same Kh/s for 160w versus 250w of a 7950.

Quote from: pieterjanvh on March 10, 2014, 09:24:49 PM

Quote from: bumface on March 10, 2014, 04:20:51 PM

Quote from: pieterjanvh on March 10, 2014, 03:58:57 PM

Bumface, is ziggy doing anything at all about the CPU mining problem?

what problem?

There's no CPU miner for UTC... And the question have been asked many, many times.
U can't advertise a coin for being GPU and CPU friendly after a while and not have a CPU miner

There are a few CPU miners. One is listed on the Ultracoin forum too. However, there is one specific miner that is best and most up to date.

-Manual N parameters for multiple coins
-X86 and 64bit formats
-Stratum pool capable
-Scrypt optimizations for Scrypt-Jane

https://github.com/thirtybird/cpuminer/releases/

This is the absolute best CPU miner out there currently. I believe it has all the needs being asked for.

Even though I'm not actively posting here; I still hate to not help if I can. Grin

Thanks
Prot

UftrEhcPx5hTY4YJvSziPi13dfZT9nXSqw

So the coin is, in essence, ''miner resistant'' no matter what device mines it. pfft, advertise asic resistant when asics won't be mainstream for another few months. This changes everything and once again, hidden and tweaked info. utc seeming more and more like a sophisticated pump and dump since all ''miner-attainable coins'' will have been mined in 1 month with millions of coin inaccessible, in the blockchain. Diff will drop dramatically when gpu's no longer able to mine, so its good for the cpu's until the next nfactor after this next nfactor in april. Then pointless to mine completely.