Java object serialization handles cycles based on object identity. On Tue, Aug 11, 2009 at 6:17 AM, fft1976<fft1...@gmail.com> wrote: > > On Aug 10, 8:19 pm, "Kyle R. Burton" <kyle.bur...@gmail.com> wrote: >> > Does all this work with cycles, Java arrays, etc.? >> >> It will work with anything that implements the Serializable interface >> in Java. Arrays do implement that interface, as do all the >> primitives. With respect to cycles, I'd suspect it does, but would >> test it. If you have a repl handy it should be pretty easy to test >> those functions out on your data structures. >> >> What class has the cycle? Is it a standard collection? >> > > Cycles are a special case of substructure sharing. Let's talk about > that instead. > > (def common [1 2 3 4 5]) > (def a [6 common]) > (def b [7 common]) > (def c [a b]) > > If you are serializing c, I want "common" to get copied only once. > > I don't know JVM too well, but I think no efficient user-level > solution is possible. Why? To take care of substructure sharing, you > need to remember a set of shareable values that have already been > serialized, and do "reference equality" comparisons when new new > substructures are serialized. > > This comparison and a set implementation can easily be done with > pointers (because you have "<"), but there are no pointers in the JVM, > and no "reference inequality", so you must use linear seeks, making > the time complexity of serialization quadratic, where in C/C++ it > could be O(N log N) > > >
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