double test(GvmCluster<S,K> cluster) {
		return m0 == 0.0 && cluster.m0 == 0.0 ? 0.0 : clusters.space.variance(m0, m1, m2, cluster.m0, cluster.m1, cluster.m2);
	}
double test ( GvmCluster < S , K > cluster ) { return m0 == 0.0 && cluster . m0 == 0.0 ? 0.0 : clusters . space . variance ( m0 , m1 , m2 , cluster . m0 , cluster . m1 , cluster . m2 ) ; }
TODO: change for consistency with other test method : return increase in variance