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Old 2022-01-19, 10:36   #26
bur's Avatar
Aug 2020

601 Posts

No new primes, just another status update:

No sieving was done since the last update.

All n < 5,600,000 have now been checked. No prime since more than 5M candidates, low weight indeed. :)

Since the FFT size grew to 640K with n > 5.6M, the 64 MB L3 cache of the Ryzen 9 3900x ran out when testing 12 numbers simultaneously. Initially I ran six 2-threaded LLR instances, but noticed that two of them were about 30% slower than the other four. The reason being the special layout of the processor. There are four so-called CCDs with 16MB L3 cache each. And since each CCD houses three cores, that means that two of the LLR instances ran on two separate CCDs.

So I switched to four 3-threaded LLR instances occupying a single CCD each. Maybe special constructs like 4 2-threaded and 4 single-threaded LLRs would lead to a higher throughput, I didn't run any tests.

Smallest LLR-test currently running:
n = 5.62M
FFT = 640K
duration = 4060 s / test
digits = 1.69M
Caldwell entry rank: 241

Largest LLR-test currently running:
n = 5.65M
FFT = 640k
duration = 4090 s / test
digits = 1.70M
Caldwell entry rank: 238
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