RE: Mersenne: Prime 95 Error Messages/ Misc
General comments on overclocking and Prime95: If you're overclocking a CPU, it is a good idea to run the full Prime95 self test (Options menu) to ensure that the CPU is stable and functional for all FFT lengths. This is especially important if you are using a Xeon processor, as there are interesting cache functionality problems that only appear when a certain percentage of the die is used. Note: This behavior appears even more often on the latest Intel Coppermine processors -- only Xeon-like configurations checked so far. It is also possible to have an overclocked CPU pass the full self test suite, but later exhibit problems. The likely culprit is simple wearout -- the CPU initially was barely functional at the overclocked speed, but slowed enough that it no longer runs. If this happens, you usually can still run the CPU at the rated speed. Regards, Ethan -Original Message- From: [EMAIL PROTECTED] On Behalf Of Aaron Blosser I also got the "illegal sumout" and it locked up my machine. It did it four times in a row at the 6564090 iteration (the lock ups were hard locks - had to recycle power to recover). However, I had my pentium-II 266 overclocked to 333, and when I reset the speed back to 266 the problem went away. I have had it overclocked for about 5 months now with no problems. I have been running prime95 at 333mhz since 16 May 99. After resetting the speed to 266 I went back to an older backup file (and lost about 4 hours work) just to make sure I am still working with good data. Interesting to note -- the average iteration speed at idle (0.275 sec) remained unchanged regardless of the CPU speed change. Does overclocking even help? Maybe this error is a bug, maybe a hardware error, although the latter seems more suspect in my case. I've seen this happen a lot on computers that are either overclocked or just have a faulty CPU/memory module. For instance, I've got a nice IBM PPro 200 machine that's been running NTPrime for nearly a year now, rock solid, nary a problem. On a whim, I thought I'd see if the machine could handle 233MHz. Everything else ran okay, NT, Office, etc. but NTPrime started kicking out errors like a banshee. [SNIP] Anyway, long and short is that overclocking might seem to work fine, but a really CPU intensive program like NTPrime/Prime95 is likely to show problems. Heck, it's a great way to find out if your overclocked system is really working as well as you thought...just back up any temp files beforehand so you can revert back to them when/if you start getting errors. [SNIP] Aaron Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Mersenne: Re: [First 10 million digit exponent]
On Tue, Jun 08, 1999 at 11:53:30AM +0200, Alex Kruppa wrote: The math is really quite simple: a number n has log_10(n) (logarithm with base 10) decimal digits or ld(n) (ld = log_2 = logarithm with base 2) bits. You can do a base conversion between logarithms from base a to base b by dividing log_a(n) by log_a(b). The log_10(2) =~ 0,301 =~ 1 / 3.3219. So if you want to know the number of bits in a 10,000,000 digit number, you do 10,000,000 / log_10(2) =~ 10,000,000 * 3,3219 = 33,219,000. Looks like I shouldn't have asked this question, I'm getting flooded with replies here :-) The exact formula (as Brian pointed out) is: ceil((x-1)/log10(2)) Set x=1000, and you get an exponent of 33,219,278 (at least that's what gcc and my assembly program tells me, Brian found it to be 33,219,277). The first prime exponent Mersenne with 10,000,000 digits is M33219281. And below M3600, there are 159,975 exponents (again repeating Brian) with at least 10 million digits. /* Steinar */ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: Re: [First 10 million digit exponent]
L.S., And below M3600, there are 159,975 exponents (again repeating Brian) with at least 10 million digits. Fine, but are the efforts being made in that region centrally registered? YotN, Henk Stokhorst. Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: Prime 95 Error Messages/ Misc
Hi, At 04:39 PM 6/7/99 -0700, J. Williams wrote: Error: Illegal Sumout This error can be a hardware problem, but is very often caused by a faulty driver or program (usually related to the audio card). Is this anything I need to be concerned about and is there a listing of such messages? This error and the others are briefly discussed in the readme.txt file. Prime95 recovers from ILLEGAL SUMOUT ERRORs quite well, so there is little to be concerned about. If you get either of the other two errors, then almost certainly you have a hardware problem, and a cause for concern. Also, a while ago the program reserved about 20 numbers for testing (all the way into the year 2001) then it and released them a few minutes later. Is this normal operation? No. It is possible the program misguessed your CPU speed (say it thought you had a 2000 MHz Pentium), reserved a lot of exponents to keep you busy, and then when your actual progress was less than expected it returned the excess exponents. Any tips for optimization and usage? No, there really is little you can do other than remove screen savers and power save features that slow the CPU speed down. Finally, when and why does it communicate with the server (besides getting new numbers to test)? Every 28 days it checks in to let the server know you are still working on the number. It may also call in to let the server know of any changes in the expected completion date. Best regards, George Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Mersenne: These go to 11 (WAS: blahblah...)
Paul Leyland [EMAIL PROTECTED] wrote:
The radix is always 10.
{snip}
or, more concisely, (1+1+1)^(1+1) + 1.
Can anyone represent that number in fewer than (1+1+1)! ones?
How about
1 1,
where the shift is, of course, decimal.
Your shifty friend,
-Ernst
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Re: Mersenne: Prime 95 Error Messages/ Misc
The system I built/overclocked is a Pentium-II 266 with a Shuttle Computer International HOT-641 motherboard and 256 megs of 10ns RAM. The original bus clock speed was 66 mhz which I upped to 83 mhz in the BIOS Configuration Utility. I had to remove the case and train a 3" desk fan on the CPU to keep it cool enough to run at 333 mhz but the 20% increase in speed was worth it. I ran a burn-in test on it for 2 solid days when I first overclocked it to make sure I didn't have a weak processor, and when I started Prime95 I tortured it for about a half of a day with no errors so I figured it was good to go. I think the problem is heat-related, due to the onset of hotter months in this climate and the poor ability of our air conditioner to handle the heat. I have since started looking at P2-450mhz processors because adding an extra 20% to the Prime # "expected completion date" test time after having a shorter completion time is rather irksome. Thanks to all the list members who offered different and vaild viewpoints as to the nature of the problem. I have since configured my reported CPU speed in Prime95 back to 266 (which I forgot to do), and the reported time between iterations increased to a more accurate figure. Gary Diehl Brian J Beesley wrote: It is also possible to have an overclocked CPU pass the full self test suite, but later exhibit problems. The likely culprit is simple wearout -- the CPU initially was barely functional at the overclocked speed, but slowed enough that it no longer runs. If this happens, you usually can still run the CPU at the rated speed. Or, the errors are there all the time but at a low rate e.g. on average 1 every day. This is very likely to pass the 1 hour "self test" but will show up in actual use, or on the continuous "torture test" (see the "Options" menu in Prime95). If you've overclocked your system at all (_not_ reccomended, but I know it can be successful in some cases) then I suggest you let the torture test run for a couple of days before committing yourself to doing "real" work. It can happen that an overclocked system appears to run fine for "office" applications but causes problems with Prime95 because very few other applications use the floating- point unit even half as intensively as Prime95 does. Note that simple overheating can also cause problems, even if your system _isn't_ overclocked. Might be an idea to check that case and processor cooling fans are operating. They have been known to fail! Finally (I think this is right - I'm sure George will chip in if not) there is a small but finite chance that you could get a very occasional "sum out error" even if your system is 100% perfect. This is due to abnormal combinations of data in the FFT triggering the "sanity check" in the code; the result may well be OK. The program should check that the "error" is "deterministic" (repeatable) rather than random and continue automatically if it is - though there will be an error log entry - PrimeNet uses this information to flag the result as "suspect", the exponent should then be re-assigned for an early double-check instead of waiting its turn as usual. Regards Brian Beesley Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
