Sieving discussion thread

[Oddball]

Originally Posted by Ken_g6

FYI, I have a new version of TPSieve out, based on and in the same archive with the newer PPSieve, v0.3.10 (source)

Despite being newer, this version is unfortunately a little slower in many cases. But it's likely to be faster for people with AMD processors.

On my Phenom II X6 1055T:

32 bit SSE2 old version: 138M p/sec
32 bit SSE2 new version: 131M p/sec

64 bit old version: 85M p/sec
64 bit new version: 163M p/sec

Good job!

[mdettweiler]

I just noticed something rather odd with tpsieve (CPU) today. All along, I have been using a batch file to run the tpsieve commands for my sieving ranges here, and currently it looks like:

tpsieve-x86-windows-sse2.exe -i 480000-484999_30aug2010.txt -p 1450e12 -P 1455e12 -N 485000

As in the officially suggested command line from the variable-n sieve reservation thread, I have the "-N 485000" parameter on there. But, I got to thinking just now that it was really rather redundant since we're running with a sieve file. So, I tried leaving it off once, and was surprised to see that memory usage jumped to over a gigabyte! Normally, it's only 25MB or so once it gets into the main sieve loop. Needless to say, I changed it back and restarted the program right away (having only 2 GB of total RAM in the system).

Ken, any idea why this is? At first I thought that including the "-N 485000" parameter might be forcing it into no-sieve-file mode, but that can't be since it takes a good 45-60 seconds to load the sieve file each time I run the program. Surely it would be skipping that part if it was really running without a sieve file. Yet if it's got the whole sieve file in there somewhere, how come it's only using 25 MB of memory? (FYI, it does have 1 GB of virtual memory allocated...though that would raise the question of why all that's in virtual memory with -N 485000, but in active memory without it.)

[Ken_g6]

Originally Posted by mdettweiler

(FYI, it does have 1 GB of virtual memory allocated...though that would raise the question of why all that's in virtual memory with -N 485000, but in active memory without it.)

That would seem to be the correct question. -N might crop out some N's from the sieve file that aren't in the range you want to sieve. That would save memory, but it would also decrease the virtual memory use.

Edit: The reason to use -k, -K, and -N (and -n? I'll have to check on that.) is to avoid a first pass on the sieve file to find those values.

[mdettweiler]

Originally Posted by Ken_g6

That would seem to be the correct question. -N might crop out some N's from the sieve file that aren't in the range you want to sieve. That would save memory, but it would also decrease the virtual memory use.

Edit: The reason to use -k, -K, and -N (and -n? I'll have to check on that.) is to avoid a first pass on the sieve file to find those values.

Hmm, I see. Might the "first pass" on the sieve file load it into active memory, but the "second pass" into virtual memory if the former wasn't done already--even though the end result is of course the same (possibly a bug)?