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-   -   ECM Stage 2 RAM (https://www.mersenneforum.org/showthread.php?t=23789)

storm5510 2018-11-08 12:47

ECM Stage 2 RAM
 
As most know, the minimum RAM size for any stage 2 process in [I]Prime95[/I] is 8MB. Assignments are based on whatever the amount is As I take the size up, the exponent values increase. When this happens, the smaller exponents, < 100,000, are eventually bypassed. Is there a way to compensate for this?

petrw1 2018-11-08 16:01

This might be a new "feature".

Several years ago I used to set RAM really now; get assigned a bunch of LOW ECM work; stop Prime95 and increase the RAM and start it so they would finish faster.

storm5510 2018-11-08 16:30

[QUOTE=petrw1;499903]This might be a new "feature".

Several years ago I used to set RAM really now; get assigned a bunch of LOW ECM work; stop Prime95 and increase the RAM and start it so they would finish faster.[/QUOTE]

This is where I run into a wall, of sorts. If I go above a certain point, [I]Prime95[/I] begins to pause during stage 2. Going any higher decreases the time between pauses and increases the pause time. It eventually becomes self-defeating. P-1 stage 2 does [U]not[/U] do this! I suspect this is unique to my setup.

The cutoff seems to be in the 48MB to 64MB range. This is not a problem with smaller exponents, regardless of the RAM setting. By smaller, I mean anything at, or below, six digits.

What it does during these pauses, I have not a clue. All I can say is that there is no hard drive activity and everything else responds properly. This applies to Windows 7 and 10, both x64.

Perhaps I need to do some experimentation with the RAM settings in the BIOS. Something is amiss and I would like to find it.

VictordeHolland 2018-11-08 22:42

Maybe I don't understand your question entirely, but if you want to manually do ECM on a exponent, you can just add it to your queue with:
ECM2=1,2,exponent,-1,B1,B2,numbersofcurves,"knowfactorn,knownfactor"
for instance:

ECM2=1,2,1682911,-1,250000,25000000,3
will let Prime95 do 3 ECM curves on 2^1682911-1 with B1=250e3 B2=25e6

lycorn 2018-11-09 00:05

Seconded.
If you do that, you may test whatever exponent you wish, regardless of the RAM size assigned to Prime95. Of course, if you are testing very small exponents, the amount of RAM needed will be very low, but it´s good practice to have a generous amount assigned to Prime95, in case you decide to test larger exponents.
I am curently running curves on M8581, and the program is using only 431 MB for Stage 2, but this is a very small exponent. If you test exponents in the 2M range, for example, the amount of RAM used wll jump to a couple of gigabytes.

petrw1 2018-11-09 00:37

I did this a while back because I didn't want the hassle of manually entering assignments.

In my case I wanted ECM-Fermat assignments and I noticed that for my specific PC that GhzDays per Day was noticeably more generous with the smaller assignments (up to about 131072) but I also noted that the RAM I needed to specify for Prime95 to give me assignments this low was less than ideal to quickly complete these.

So I would set RAM to about 100; get 30 days worth of low ECM-F; then set RAM to about 2,000.
Rinse and repeat monthly.

storm5510 2018-11-09 13:12

[QUOTE=VictordeHolland;499934]Maybe I don't understand your question entirely...[/QUOTE]

Forgive me. I went a bit off target with this.

[QUOTE=petrw1]So I would set RAM to about 100; get 30 days worth of low ECM-F; then set RAM to about 2,000.[/QUOTE]

What I do, is allow [I]Prime95[/I] to get the assignments it wants based on the memory allocation, then I go into the preferences and set days of work to zero. Then, I can take the RAM up. It reports each completion, but does not reserve more as it goes along.

I found something in relation to the pausing in stage 2. This system BIOS has two memory settings, Auto, and XMP or "eXtreme Memory Profile." Setting it to XMP creates a drop-down list of options which includes the RAM speed. The rest, I do not understand what they are. No worry. On the XMP setting and not changing anything else in the list, the pause times are greatly reduced.

I have been testing with the RAM set to 512MB and exponents > 1,000,000. The pause time is about 1.1 seconds for every 7%. It can complete each test in about eight minutes. If I drop this to 256MB, it takes nine minutes to complete on slightly smaller exponents. I do not see any pauses.

About setting it to get 30 days of work: In my case, 15 is about the maximum number that it will maintain. I will give this another try.

storm5510 2018-11-10 15:08

A couple of questions:

Take the assignment below from my HP:

[CODE]ECM2=<ID>,1,2,109229,-1,250000,25000000,3,"7680983281,2929719921407"[/CODE]

(1) The values at the end, in quotes, are known factors. Does [I]Prime95[/I] continue if it finds one of these, or does it stop?

(2) Is there a rule-of-thumb for determining the B! and B2 values? All I know is that B2 is approximately equal to B1 x 10.

Thank you! :smile:

GP2 2018-11-10 16:09

[QUOTE=storm5510;500032](1) The values at the end, in quotes, are known factors. Does [I]Prime95[/I] continue if it finds one of these, or does it stop?[/QUOTE]

No, it ignores those and keeps going.

Note: if the program finds a [I]new[/I] factor not in the list of known factors, then the ECM assignment will terminate, unless you put [c]ContinueECM=1[/c] in your [c]prime.txt[/c] file, in which case it will finish doing all the curves specified in the worktodo line (in your example, 3), possibly finding additional factors.

[QUOTE](2) Is there a rule-of-thumb for determining the B! and B2 values? All I know is that B2 is approximately equal to B1 x 10.[/QUOTE]

Actually it's B1 × 100, and your example reflects that. That is a commonly used rule of thumb, although other values are possible.

You can look at the [URL="https://www.mersenne.org/report_ecm/?txt=0&ecmnof_lo=109000&ecmnof_hi=110000&ecm_lo=109000&ecm_hi=110000"]ECM Progress report page[/URL], setting the appropriate exponent range you're interested in, to see how much ECM has been done already and with what parameters.

storm5510 2018-11-10 17:02

[QUOTE=GP2;500038]...Actually it's B1 × 100, and your example reflects that. That is a commonly used rule of thumb, although other values are possible...[/QUOTE]

Thank you for your reply!!!

My example shows 250,000 and 25,000,000. What happens if I were to narrow this range? An example might be lowering B2 to 2,500,500. Based on what I've seen, B1 seems to be much more important than B2.

A shot-in-the-dark: These are bounds for calculations using the seed value that appears at the start of Stage 1. If this is not the case, then I am unsure how they are used.

I apologize for going somewhat [U]off-topic[/U] with this!

science_man_88 2018-11-10 17:30

[QUOTE=storm5510;500041]Thank you for your reply!!!

My example shows 250,000 and 25,000,000. What happens if I were to narrow this range? An example might be lowering B2 to 2,500,500. Based on what I've seen, B1 seems to be much more important than B2.

A shot-in-the-dark: These are bounds for calculations using the seed value that appears at the start of Stage 1. If this is not the case, then I am unsure how they are used.

I apologize for going somewhat [U]off-topic[/U] with this![/QUOTE]
[url]https://en.m.wikipedia.org/wiki/Lenstra_elliptic-curve_factorization[/url]


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