RFR [8005953] Speedup construction of CopyOnWriteArraySet in special cases (original) (raw)
Ivan Gerasimov ivan.gerasimov at oracle.com
Tue Apr 30 11:41:13 UTC 2013
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Hello everybody!
Would you please review my proposal to change constructor of CopyOnWriteArraySet? http://cr.openjdk.java.net/~dmeetry/8005953/webrev.0/ <http://cr.openjdk.java.net/%7Edmeetry/8005953/webrev.0/>
Currently, the body of the constructor is like this: al = new CopyOnWriteArrayList(); al.addAllAbsent(c);
The addAllAbsent() function has O(c.length^2) complexity, so construction time quickly grows with the input size. However, if we knew that c is a Set, we could construct the COWAS in linear time. And if the c was known to be another COWAS, we could simply clone the underlying CopyOnWriteArrayList.
The webrew also includes a test I used to make sure nothing is broken.
Sincerely yours, Ivan
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