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POHow should I deal with a very large array in Java?
 

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  1. POHow should I deal with a very large array in Java?
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    <p>I have an algorithm which currently allocates a very large array of doubles, which it updates and searches frequently. The size of the array is N^2/2, where N is the number of rows on which the algorithm is operating. I also have to keep a copy of the entire thing for purposes associated with the application surrounding the algorithm.</p> <p>Of course this imposes a limit on the number of rows that my algorithm can handle as I have the heap limitation to contend with. Up to this point I have got away with asking the people using the algorithm to update the -Xmx setting to allocate more space, and that has worked fine. However, I now have a genuine problem where I need this array to be larger than I can fit into memory.</p> <p>I already have plans to change my algorithm to mitigate the necessity of this large array and have some promising results in that domain. However it is a fundamental alteration to the process and will require a lot more work before it gets to the highly polished condition of my current code which is operating in production very successfully and has been for several years.</p> <p>So, while I am perfecting my new algorithm I wanted to extend the life of the existing one and that means tackling the heap limitation associated with allocating my huge array of doubles. </p> <p>My question is what is the best way of dealing with it? Should I use an nio FileChannel and a MappedByteBuffer, or is there a better approach. If I do use the nio approach, what sort of performance hit should I expect to take compared to an in-memory array of the same size?</p> <p>Thanks</p>
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    1. COI don't suppose you could just process the data in chunks?
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    2. COUnfortunately not with this implementation. That is what my new implementation does, but there are a whole host of further problems associated with combining the chunk results back together.
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    3. COhave you considered using a database?
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