I ran 18 CPUs for the past 380 blocks (i5 CPUs, 3rd Generation, 4 threads, 50 Watts each, 7.4 Sol/s for 4 threads, 2.1 Sol/s for 1 thread) using the default tromp solver that was in the rc4 beta and got zero blocks.
The network hash rate is
Sol/s = Difficulty / 8.823 = D x 17 / 150
So, with 18 CPUs x 7.2 / ( D / 8.823) where D was about 250,000, I expected to get 0.0046 of the 380 blocks, which is 1.7 blocks. So there's no big surprise I did not get any blocks.