Re: Concurrent bidirectional one-to-many map?

From:
Robert Klemme <shortcutter@googlemail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 11 May 2011 04:55:29 -0700 (PDT)
Message-ID:
<d5e1219d-70bd-4171-ad5d-337c6b15a84b@e35g2000yqc.googlegroups.com>
On 11 Mai, 10:51, Sebastian <sebast...@undisclosed.invalid> wrote:

Am 11.05.2011 10:09, schrieb Sebastian:

Here's a bit of the WorkspaceManager code referred to above:

public void closeWorkspace( UUID id )
{
  writeLock.lock(); // <<<<<<<<<<< necessary ?
  try {
   Workspace wp = wpMap.remove( id );
...


As afterthought to my immediately preceding post,
let me add that it would be nice if we could process
unrelated workspaces in parallel. How about having a
ReentrantReadWriteLock associated with each workspace,
and using themlike this:

   Workspace wp = wpMap.get( id );
   wp.writeLock.lock();
   try {
     wpMap.remove( id );
     ...

Wouldn't this improve things?


You said you can't modify Workspace and Task. If you create wrapper
classes then you need synchronization when managing the mapping from
original to wrapped. Sorry, I don't have time to go into more detail,
but externally adding state in a thread safe but still scalable manner
is tricky (unless you code Ruby that is ;-)).

Cheers

robert

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