[Mono-devel-list] PATCH: Lazily allocate ArrayList buffers

Ben Maurer bmaurer at users.sourceforge.net
Sun Feb 15 01:10:45 EST 2004


Attached is a patch that makes ArrayLists allocate their buffers only on
the first addition to the list. For example the following code:

ArrayList ar = new ArrayList ();
ar = null;

will not allocate an object [].

Running the profiler on a few applications, it seems that the patch has
some effect. One notable example is MonoDevelop where it prevented 2/3
of the allocations of arraylists.

It seems that MS implements this behavior in the v2 framework. Using a
beta of the code, I ran:

ArrayList ar = new ArrayList ()
COnsole.WriteLine (ar.Capacity);

It returned 0. This seems to indicate that the capacity (which is the
size of the array) is zero until something has been added.

For my patch, I made it so that the outside behavior would not change,
the code fudges having a 16 capacity when the list is empty. Our nunit
tests probe for this case. However, I wonder if we really should do

The nunit tests pass after the patch.

-- Ben
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