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-   -   Questions about RAM and Prime95 (https://www.mersenneforum.org/showthread.php?t=2157)

Matthias C. Noc 2004-02-29 17:48

Questions about RAM and Prime95
 
I’ve some questions about the RAM use of Prime95. I’ve allocated 56 MB for daytime use, but the task-manager shows that only between 14 and 16 are normally used while the long LL-test is running. Is there a way to fix the maximum RAM the program needs during this phase? It will take about three weeks to finish the LL-test, so I would reduce the amount of allocated RAM until the P-1 tests need again all the RAM they can get. Does a larger exponent need more RAM or why are is the used RAM changing between 14 to 16 MB? I guess it should be the same kind of operation and so the same amount of resources needed for that. If Prime95 is needing less RAM then allocated is it using this smaller amount only or are the other MB still blocked?

Thanks,

Matt

cheesehead 2004-02-29 23:14

[QUOTE=Matthias C. Noc]I’ve allocated 56 MB for daytime use, but the task-manager shows that only between 14 and 16 are normally used while the long LL-test is running.[/quote]
The only time that the "Daytime available memory" and "Nighttime available memory" settings are used while Prime95 processes your PrimeNet assignments is during P-1 factoring stage 2 (not stage 1). During P-1 stage 2, Prime95 allocates extra buffers for temporary storage areas in addition to the basic two buffers that it always needs. (Prime95 always needs two basic buffers, each long enough to hold the Mersenne number on which it is working.)

During LL-testing, Prime95 pays no attention to what available memory you've specified -- it simply uses the minimum amount of RAM that it needs to perform the LL-testing and does not allocate any extra work areas. The same is true during P-1 stage 1.

During LL-testing (or P-1 stage 1), your specification of 56 MB for available memory does no harm and does not cause Prime95 to use any more memory than the minimum amount it needs during those phases.

[quote]Is there a way to fix the maximum RAM the program needs during this phase?[/quote]
No. There's no need to do that for LL-testing. The program uses only the minimum RAM necessary during that phase.

[quote]It will take about three weeks to finish the LL-test, so I would reduce the amount of allocated RAM until the P-1 tests need again all the RAM they can get.[/quote]
No need to do that. In fact, it's better that you leave your "Daytime available memory" and "Nighttime available memory" settings alone once you've decided how much to make available for P-1 stage 2 -- when Prime95 doesn't need them they won't make any difference, and when it does need them it's better that you have them set in advance.

[quote]Does a larger exponent need more RAM or why are is the used RAM changing between 14 to 16 MB?[/quote]
Yes, a larger exponent requires more RAM than a smaller exponent.

[quote]If Prime95 is needing less RAM then allocated is it using this smaller amount only or are the other MB still blocked?[/QUOTE]
It uses only the smaller amount. If you specified that 56 MB are available (for P-1 stage 2), and LL-testing needs only 14 MB, the "extra" 42 MB are simply not requested by Prime95, are not blocked, and are available for any other program to use at the same time.

Matthias C. Noc 2004-03-01 08:16

Thanks!


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