pfgw factorial testing too slow?

[bur]

I had done some factorial prime testing with PRPnet with i5 and i3 CPUs before and a test took about 25-30 hours.

Now recently I began testing using an i10-10900k and a test in the 282000! range takes more than 40 hours. I have no idea why.

FFT is about 450k, it's a 10 core with 20 MB L3 cache, I'm running 10 tasks simultaneously. It's not ideal, but better L3/task ratio than on the other computers.

It's running Ubuntu. I tried different pfgw versions, the one supplied with the PRPnet client (3.7.10) and also 4.0.1 from sourceforge. No difference.

Each pfgw instance is using 99-100% of a core. Total RAM usage is 1GB/16GB. I used that same computer for yafu and cado and never had any issues with slow speeds.

[axn]

Originally Posted by bur

a test took about 25-30 hours.

It would be helpful if there was some indication of the sizes of the numbers being tested when you were getting the above timings.

For example, n=280k ought to take appr. 35% more time compared to n=250k (based on naive scaling calculations) on the same CPU. Of course, it would be worse, since the impact of large L3 will be less when you have bigger FFT.