dfm/emcee — Issue #12: Multithread speed scaling
Author: pirg
Created: 2012-02-20 10:10:07+00:00
State: open

Hi,

Running the basic quickstart example and checking the computation time for increasing thread numbers, I seem to get the counterintuitive results that computation time increases with increasing thread numbers.

Here are some quick benchmark results on a 8CPU machine.
nthread: time to completion
1: 4.2 sec
2: 9.1 sec
4: 11.9 sec
8: 12.8 sec

Furthermore, looking at the CPU usage, I always seem to get ntread+1 processes, the first one taking 100% of a CPU and the nthread others sharing about 1/nthread of ONE of the other 7 CPUs.

Any idea of what going on ?
Pierre