Much time on " initializing source particles..."

Hi,

I just run the c5g7 benchmark with OpenMC, the particles number in my settings is 1000. Since the computation runs on my desktop, I understand I will cost a lot of time.
But I find out that it costs much more time on the initializing source particles process, compared with the actual simulation time. I am not sure if this is normal or not? Or is there any way to accelerating this process.

Also, during the initializing, my CPU utilization is only 25% (one thread used), although I already set my OpenMP thread to 4. So, it seems that it doesn’t make use of the full potential of my processor.

Best,

Tian