Update FAQ.md

FAQ.md

@@ -19,3 +19,6 @@ Another way to avoid this is running main.py directly (i.e. `python main.py ...`
 
 **Question**: Quite often I would like to stop and restart spearmint. Sometimes I can Ctrl-C spearmint and restart it. Other times it seems to block and do nothing when restarted. Is there anything I can do except cleanup the directory and start from scratch again? Also Ctrl-C only seems to break me out of spearmint, a spearmint process is still running in the background (which I kill manually). Is this expected?  
 **Answer**: Spearmint uses a file `expt_grid.pkl` to maintains state.  All the jobs spawned by spearmint write to this file as well as spearmint itself.  This enables spearmint to spawn jobs on multiple nodes in a cluster.  Of course, the writes to this file must be atomic.  When you kill spearmint, the jobs it has spawned will keep running (this is the intended behavior - the assumption is that jobs are expensive, so something that kills spearmint hopefully wouldn't stop the running jobs).  There is a caveat that spearmint may die when it is holding the lock to this `expt_grid.pkl`.  If you find that you restart spearmint and it is perpetually "waiting to lock grid..." you can safely remove the lock by typing `rm <expt_dir>/expt_grid.pkl.lock`.
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+**Question**: Spearmint locks up after performing the first sampling computation.
+**Answer**: Python's multiprocessing causes a deadlock on some platforms.  You can pass in a command line argument '--method-args=multiprocessing=0' to turn off multiprocessing and do computations serially (this is a bit slower but works just as well).