Selection Algorithm
No synthetic	44.36 ± 1.51	47.33 ± 0.57	63.40 ± 1.33
Center matching	50.04 ± 2.84	53.83 ± 0.59	67.01 ± 0.89
Center sampling	50.48 ± 2.03	54.91 ± 1.07	67.71 ± 0.90
DS3	52.83 ± 2.19	58.32 ± 0.43	68.21 ± 0.66
K-means	50.74 ± 1.77	56.06 ± 0.68	66.50 ± 1.11
Random	49.38 ± 2.43	54.89 ± 0.91	67.65 ± 0.77
Text matching	50.94 ± 1.40	55.17 ± 0.57	67.81 ± 0.76
Text sampling	50.28 ± 1.18	54.82 ± 0.72	67.45 ± 1.02
Covariance matching Ours	54.00 ± 1.89	59.77 ± 0.61	69.20 ± 0.56
Real upper bound	61.08 ± 2.54	65.38 ± 0.51	74.35 ± 0.56