Selection Algorithm
No synthetic	44.36 ± 1.51	47.33 ± 0.57	63.40 ± 1.33
Center matching	53.46 ± 1.95	57.67 ± 0.58	66.52 ± 0.81
Center sampling	50.15 ± 1.79	56.05 ± 0.65	65.38 ± 0.98
DS3	54.15 ± 2.17	59.43 ± 0.73	66.00 ± 0.94
K-means	51.63 ± 1.29	56.77 ± 0.89	65.23 ± 0.61
Random	51.26 ± 1.96	55.27 ± 0.74	65.24 ± 1.01
Text matching	51.20 ± 1.82	56.08 ± 0.57	65.93 ± 0.59
Text sampling	50.31 ± 1.70	55.79 ± 0.68	64.93 ± 1.12
Covariance matching Ours	54.45 ± 2.11	59.17 ± 0.64	66.69 ± 0.70
Real upper bound	61.08 ± 2.54	65.38 ± 0.51	74.35 ± 0.56