Error when reading/writing hashmap from two threads about jdbm3 HOT 8 CLOSED

I think it is not supposed to be thread-safe, and you have to synchronyze read/write methods from JDBM collections. (java.util.HashMap is not thread-safe also ...)

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Collectios should be thread safe and this is a bug. I am going to fix it soon.

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Sorry about that :). Then I hope there will be no impact on performance for single threaded access.

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no impact on performance for single threaded access.

JDBM3 uses read/write locks, so there is some overhead for single threaded apps. But this overhead is minimal compared to others (diskIO, serialization..).

My main priority is performance with single thread access, and I am not going to complicate design to gain a few % on multicore tests.

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I've seen that jdbm2 has a THREAD_SAFE option. Perhaps that could be added to DBMaker

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THREAD_SAFE in JDBM2 is fragment from previous versions and is not really used. Overhead of creating and maintaining this option would also be bigger then benefits. As I said overhead of synchronization is very small.

In future I may start using preprocessor which would remove locks and produce single-thread-optimized jar.

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Fair enough. What's interesting is that if both threads use the same instance of the map, everything works.

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Fixed, problem was caused by two different instances of 'Map', now it uses weak reference to garantee only single instance

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