[Math] Cloning statistics

[Ken Geis]

I'm playing with commons-math to implement a data mining algorithm and I 
am having a performance problem.

I am doing running statistics over an ordered set of data, storing the 
statistics at each new value I come across.  One way of doing this would 
be to have an array of SummaryStatistics and do

for (int i = 0; i < length; i++)
{
    for (int j = i; j < length; j++)
    {
        statsArray[j].addValue(values[i]);
    }
}
another way is to do

for (int i = 0; i < length; i++)
{
    stats.addValue(values[i]);
    statsArray[i] = SerializationUtils.clone(stats);
}
A lot of these objects are marked Serializable, but clone methods do not 
exist.  That's why I use commons-lang SerializationUtils. 
Unfortunately, that makes the cloning take up 50% of my runtime because 
(de)serialization is expensive.

I will probably patch the statistics classes, implementing enough of 
clone() to make me happy.  Would you like this patch?



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