Safely writing to the same file in parallel foreach loop

[Joseph Rushton Wakeling]

On 11/15/2012 12:44 AM, Joseph Rushton Wakeling wrote:
> In the application I have in mind, there is a LOT of work that would be done
> within the parallel foreach loop -- we're talking at least 20 minutes' solid
> processing before the file write takes place, so this seems an appropriate
> approach given how simple it is.

An oddity here: although the correct results seem to come out of the 
calculation, at the end, the program containing the parallel foreach hangs -- it 
doesn't stop running, even though all the calculations are complete.

Any thoughts as to why?  I guess a thread that has not closed correctly, but I 
can't see why any one of them should not do so.