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Subject: Re: Concurrent bidirectional one-to-many map?
Date: Sat, 07 May 2011 09:35:27 -0700
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On 5/7/2011 2:43 AM, Sebastian wrote:

> Now I want to be able to close a workspace, releasing all tasks
> to be assignable again to other workspaces.
>
> public void closeWorkspace( Workspace ws ) {
> // how do this efficiently? iterate over all
> // entries (holding a write lock) and remove it
> // when the value equals ws?
> }


Fundamentally, I don't see any solution other than Patricia's.  And I 
think you'll need to hold locks for atomicity over all structures 
anyway: I can't think of a different way of doing it.  Unless your 
problem can somehow tolerate finding a task as it's workspace is being 
closed, you'll have to guarantee that all operations complete before the 
next one is processed.

It really does depend on what "efficiently" means here.  I'd just use 
locks and let the JVM optimize it.  It's pretty good at that.