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    <p>I don't see anything in here that would cause a performance problem -- at least not with that high a variance. Array accesses should be extremely fast -- even if they are 4 dimensional arrays. [[Nice effort on that.]]</p> <p>A quarter second is not a huge amount of time which makes me wonder if the profiler is lying to you about the source of the problem. It may be responding poorly to the multi-dimensional arrays or some other attribute of this method that is not immediately apparent -- to me at least.</p> <p>One possibility, however remote, is that your program is swapped and these arrays are pretty big. If they aren't accessed very often is there any chance you are seeing some IO as some memory pages are swapped in?</p> <p>You commented that you are using wall-clock timers to determine that the routine takes 250ms. Are you sure that the CPU was actually executing that method for that time period? Could this be a thread contention issue that is taking over CPU in some other part of the program? Can you see if you see CPU spikes every so often when this method takes a long time?</p> <p>Any chance you are seeing a GC heap lock and it's affecting the array accesses more than other routines? Can you watch the memory graphs to see if you see a correlation? Does giving the program more heap affect the timing or the frequency of the problem? This is going to be more an issue if you are running Java &lt;= 1.5.</p>
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    1. COThe major container class retains a reference to the arrays, so I'm relatively certain they aren't being unloaded. The only large array used in this function is light[16][200][16]. For profiling, I ran timers before functions and read them afterwards to get the total time taken. I narrowed it down within function nests to this particular method, it is absolutely this. At one point, I used a substitute method which fixed the hitches but did not provide the data detail I need.
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    2. CO@Sean I've edited my answer to address the wall-clock timer issue. Yeah, `light` is not a large enough array to make a difference. That's only like ~50k. Any chance you are seeing a GC heap lock and it's affecting the array accesses more than other routines? Can you watch the memory graphs to see if you see a correlation?
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    3. COI'm certain that it's within this thread, because I went and timed several other sub-methods, and they never cause any hitch. I also timed all the other thread functions running at the same time. I'm extremely certain this has nothing to do with the GC, as I have eliminated all memory leaks from my program and I re-use nearly all of my variables as fields. Memory usage stays exactly the same once the game is running. However, if you still think this may be the case, I'd like a suggestion for which profiler to use. I am using JDK-1.6. I've given the program 30% more heap space than it requires.
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