On Wed, 16 Oct 2013 09:57:52 +0100, Sean Owen wrote:
On Wed, Oct 16, 2013 at 9:52 AM, Gilles
<gil...@harfang.homelinux.org>wrote:
I think the Comparator can also replace a
custom one in MathArrays.
Are you sure?
Yes, at least tests pass. There are two anonymous comparator classes
there
which compare by key. The new Comparator compares by key too (and by
value,
but this shouldn't hurt as the current code doesn't care about
ordering
among pairs with the same key). Collections.reverseOrder() can be
used to
reverse the Comparator too.
The potential problem is performance. The current code for
"sortInPlace" is
not as fast as it could be, very probably because it uses a Comparator.
IIUC,
using your new comparator will add another "if" (to test whether
comparing the
"value"s is necessary). [And "reverseOrder" will also add a few
operations on
its own, I guess.]
It would be nice to know whether the impact is really fairly
negligible, or
not.
There is a class (in the "test" part of repository) for performing
simple
benchmarks:
org.apache.commons.math3.PerfTestUtils
that tries to provide fair comparison results by interleaving calls to
two
(or more) alternative codes.
Best regards,
Gilles
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