not really a test, but measuring time one scaling up cluster size up to 512 nodes
gitignore intellij files
findByClusters was the time consumer.
make a hashmap with ClusterPair names (symmetric) and cut computing time by order of magnitude (1min to 1s for 256 random cluster)

perf before/after on cluster size from 2 to 512 columns
# ORIG
Running com.apporiented.algorithm.clustering.ClusterPerfTest

cluster.size    time.ms
2       3
4       0
8       5
16      25
32      56
64      240
128     3253
256     51018
512     969193

Heap size 760M

#NEW
cluster.size    time.ms
2       3
4       1
8       2
16      11
32      36
64      56
128     131
256     726
512     10167

Heap size 270M
Merge pull request #4 from alexmasselot/master

pushing up the speed