Re: Mersenne: Prime95, Prime Server and ECM factoring

1998-12-11 Thread Brian J Beesley

 My home box is on the web only very intermittently.  It finished a LL test
 several days ago and did not have another exponent ready to test, so I set
 it going on some ECM factoring.
 
 Just now, I started the dial-up connection and tried to upload the LL result
 manually, with no discernable effect whatsoever.

Was there a prime.spl file? When you say you tried to upload 
manually, do you mean you have "Do not contact PrimeNet server 
automatically" checked in Advanced/Manual Communication, and 
that you then selected Advanced/Manual Communication/Contact 
Now? Was the system actually on line at the time, if not do you 
have auto-dial enabled in Windows Dial-Up Networking?

 I then stopped the ECM curve and tried again.

When Prime95 is running a LL test or factoring assignment, it 
doesn't respond instantly to a "connect now" request. I think it waits
till it gets to a point where it can write a checkpoint file. This 
sometimes takes up to a minute. Now, ECM does not use 
checkpoint files (at present), so maybe it doesn't know how to 
interrupt itself to make the PrimeNet connection, unless you leave 
it long enough for the current curve to complete. :-(

Perhaps this "buglet" (or unwanted feature) is another reason why 
a small change to Prime95 might be indicated. What I'm thinking of 
is that, when the (low priority) computing task detects that a 
connection to PrimeNet is neccessary, it forks off a new task 
(which should run at normal priority) to handle the connection. The 
new task can die as soon as its job is done. The point here is that 
there would be no need to interrupt the computing task, and, in the 
event that a deadlock occurred in the PrimeNet comms, time would 
not be lost with the computing task stalled.

 This time, the server was "busy" (Error 23 returned)

If the last thing I wrote is wrong, then maybe either there already was a
connection from your machine to the PrimeNet server, and trying to 
start another caused it to get confused. Probably confused enough 
to reset the connection i.e. terminate it, unless special recovery 
handling is built in. So it works next try...?

 and Prime95 V16.4.1 started a new ECM curve; the effect was 
reproducible.  I
 know the server was ok, because I was looking at various status pages.

Well, it *would* start a new curve - this is normal behaviour...
 
 The workaround is to rename the worktodo.ini file in the Prime95 folder and
 to re-run the manual communication.  My LL result is now on the server and
 I've been allocated a new exponent.

You could also exit Prime95, stick a line at the top like

DoubleCheck=11213,40

which executes very fast but causes some LL testing work to be 
done when you restart Prime95. Thus giving the manual 
communication a chance to bite (and your computer a chance to 
"discover" a Mersenne prime!). The spurious result won't hurt the 
PrimeNet server. If you look at lucas_v.txt (from the database - see 
http://www.mersenne.org/status.htm) you can even turn this into 
(more or less) useful work. There are lots of very small exponents 
which have been double-checked, but one of the residuals is very 
short, IMHO it would do no harm to have a few of these rechecked 
with Prime95 v17.

A better "workaround" is to set your "days work" (in Test/PrimeNet) 
to about twice the time between your machine's "very intermittent" 
connection to the Net. Then, look for a prime.spl file, if there is one 
(probably only 1 byte long) Prime95 wants to interact with the 
PrimeNet server - maybe it wants more work - let it contact the 
server  get some. That way, you shouldn't get into "emergency" 
(run ECM for a while) operation modes.

Not that there's anything wrong with running ECM...


Regards
Brian Beesley



Re: Mersenne: Prime95, Prime Server and ECM factoring

1998-12-11 Thread Foghorn Leghorn

From: Paul Leyland [EMAIL PROTECTED]
My home box is on the web only very intermittently.  It finished a LL 
test
several days ago and did not have another exponent ready to test, so I 
set
it going on some ECM factoring.


I run ECM with a separate copy of Prime95, stored in its own directory. 
This ends to reduce complications. I can also run ECM simultaneously 
with LL testing this way, and keep separate results files for both kinds 
of work.

This brings me to a couple of questions:

1. Is it okay to add a mark to the ECM copy's results.txt file to remind 
myself which results entries I have sent to George? I don't want to 
change the file manually if the program ever reads it and depends on its 
being in a certain format.

2. Is it less efficient to run two copies of Prime95 simultaneously one 
a single-processor machine than to run them sequentially? They share 
processor time (as reported by WinTop) equally when both are working, 
but perhaps something is lost in the need to time-share two 
FPU-intensive programs.

[Oddly enough, I have noticed that sometimes when I start the ECM copy 
of Prime95, it gets 70% to 75% of CPU time instead of the usual share of 
just under 50%. Can anyone explain why this happens?]

__
Get Your Private, Free Email at http://www.hotmail.com