MASON actually has a MutableDouble. java/mason/sim/util/MutableDouble.java You could use that. Also, don't use for(Object object : objects) -- it translates to building an Iterator, and at least as of Java 7 Iterators are still quite slow. I'd do this: final public void SparseGrid2DMultiply(SparseGrid2D theGrid, double multiplier) { Bag objects = theGrid.getAllObjects(); int len = objects.size(); for(int i = 0; i < len; i++) { MutableDouble d = (MutableDouble)(objects.get(i)); d.val *= multiplier; } } On Jun 15, 2015, at 1:02 PM, Sadat Chowdhury <[log in to unmask]> wrote: > I still have a lot of files to change, and have not actually run/tested with this new method — maybe it would throw the ConcurrentModificationException, I don’t know yet. > > I am going to look into MutableDouble — it makes more sense as far as accuracy goes. Thanks! > > >> On Jun 15, 2015, at 12:58 PM, Ernesto Carrella <[log in to unmask]> wrote: >> >> You could try populating your SparseGrid2D with either an AtomicDouble or a MutableDouble from commons-lang. >> That way you can modify them without pulling them out of the grid and putting them back in. >> >> I am quite surprised it doesn't throw a ConcurrentModification exception since you are effectively looping through a list of objects that you are also modifying (with remove() and setLocation()). I suppose MASON passes a safe copy in that bag. >> >> On Mon, Jun 15, 2015 at 5:23 PM Sadat Chowdhury <[log in to unmask]> wrote: >> Hi All, >> >> When I increased the 2D world size of my system, there was a significant slowdown of the simulation. After I investigated using a profiler, it turned out to be due to methods that scan through 2D grids that in my system are defined as DoubleGrid2D. >> >> I have started converting those DoubleGrid2D into SparseGrid2D — because it fits the description perfectly: the world can be potentially unbounded and most times there will be fewer actual objects in the world. >> >> While it was relatively easy to convert all the parts that was setting and accessing objects in the grid — I am at a point where I have a lot of DoubleGrid2D’s that used full-scanning functions like .lowerBound() and .multiply(). Supposing I have a SparseGrid2D that has only one Double object per coordinate, what would be the most efficient (fast) way to implement a function similar to multiply() ? >> >> This is what I have so far, but I am just wondering if it can be done more efficiently (faster)? >> >> final public void SparseGrid2DMultiply(SparseGrid2D theGrid, >> double multiplier) { >> /* >> * theGrid is assumed to contain one and only one Double in a given >> * coordinate >> */ >> Bag objects = theGrid.getAllObjects(); >> for (Object object : objects) { >> double val = (Double) object; >> if (val != 0.0) { >> val = val * multiplier; >> Int2D location = theGrid.getObjectLocation(object); >> theGrid.remove(object); >> theGrid.setObjectLocation(val, location); >> } >> } >> >> } >> >> Any thoughts/comments is greatly appreciated, >> Sadat.