Task	Model	Language	N-gram-based	Embedding-based	Diversity	Ours
BLEU	ROUGE-L	METEOR	BERTScore	Distinct-1	Distinct-2	Ensemble
SG	M-BERT	en->en	2.93	19.8	0.106	0.895	0.937	0.993	31.793
de->de	2.77	14.6	0.139	0.72	0.944	0.996	34.933
fr->fr	1.65	13.7	0.196	0.72	0.949	0.998	30.998
es->es	1.85	13.4	0.119	0.718	0.965	0.997	30.234
zh->zh	4.98	24.7	-	0.661	0.998	0.374	26.977
XLM	en->en	3.56	20.2	0.106	0.896	0.966	0.997	31.594
de->de	3.07	25.4	0.145	0.728	0.957	0.995	29.464
fr->fr	3.89	26.1	0.192	0.745	0.944	0.982	28.127
es->es	3.52	24.7	0.132	0.738	0.969	0.994	27.465
zh->zh	0.92	17.7	-	0.611	1	0	25.593
mBART	en->en	4.6	22.4	0.117	0.903	0.974	1	32.396
de->de	4	16.1	0.145	0.735	0.982	1	34.724
fr->fr	4.79	17.3	0.215	0.751	0.981	1	32.955
es->es	4.17	15.9	0.145	0.745	0.982	1	32.43
zh->zh	6.84	27.9	-	0.677	0.998	0.275	27.03
mT5	en->en	3.49	20.4	0.109	0.9	0.97	0.994	32.014
de->de	3.01	14.6	0.139	0.731	0.977	0.993	34.758
fr->fr	3.38	16.1	0.196	0.746	0.96	0.983	31.854
es->es	3.49	14.9	0.134	0.742	0.966	0.989	32.188
zh->zh	5.79	27.1	-	0.674	0.999	0.198	26.596
SG	M-BERT	en->en	14.47	41.4	0.204	0.9	0.923	0.992	31.192
de->de	7.75	24.8	0.226	0.759	0.95	0.995	31.709
fr->fr	6.55	22.2	0.279	0.753	0.917	0.994	29.918
es->es	9.06	25.3	0.34	0.803	0.933	0.992	32.032
zh->zh	12.07	33.9	-	0.708	0.998	0.916	27.779
XLM	en->en	18.73	44.4	0.223	0.914	0.957	0.996	32.732
de->de	9.86	36.2	0.245	0.778	0.976	0.997	29.317
fr->fr	14.82	39.3	0.347	0.797	0.95	0.991	29.82
es->es	17.38	46.5	0.375	0.829	0.953	0.996	29.435
zh->zh	15.53	36.6	-	0.727	0.998	1	28.593
mBART	en->en	21.73	47.9	0.242	0.921	0.976	0.999	34.481
de->de	13.46	31.2	0.262	0.791	0.988	1	33.59
fr->fr	16.13	34.4	0.35	0.8	0.978	0.999	33.181
es->es	19.17	38.4	0.407	0.842	0.974	0.999	34.857
zh->zh	17.63	38.8	-	0.733	0.997	0.993	28.698
mT5	en->en	20.9	46.8	0.232	0.92	0.971	0.999	33.449
de->de	13.22	30.2	0.264	0.789	0.984	1	34.218
fr->fr	17.08	33.6	0.356	0.801	0.971	0.998	33.392
es->es	19.45	37.8	0.398	0.842	0.97	0.998	34.95
zh->zh	17.85	40	-	0.737	0.997	0.999	28.712
SG	M-BERT	en->en	15.87	37.1	0.209	0.891	0.967	0.998	31.467
de->de	7.59	17.8	0.189	0.719	0.952	0.997	31.835
fr->fr	8.46	23.1	0.234	0.738	0.942	0.997	28.474
es->es	10.08	26.3	0.279	0.755	0.93	0.997	29.1
zh->zh	10.75	27.5	-	0.669	0.993	0.407	26.236
XLM	en->en	14.91	34.8	0.202	0.89	0.97	0.995	31.291
de->de	7.86	22.3	0.198	0.719	0.944	0.986	30.049
fr->fr	11.03	28.2	0.296	0.749	0.903	0.982	28.037
es->es	11.59	30.2	0.295	0.758	0.907	0.993	28.062
zh->zh	14.24	27.8	-	0.681	0.982	0.614	27.875
mBART	en->en	21.91	42.9	0.233	0.907	0.984	0.999	33.625
de->de	9.58	22.9	0.208	0.735	0.975	1	31.922
fr->fr	11.75	29.1	0.274	0.759	0.958	0.999	29.147
es->es	14.11	32.7	0.325	0.775	0.939	0.999	29.714
zh->zh	16.58	33	-	0.699	0.983	0.641	27.202
mT5	en->en	17.54	38.3	0.217	0.899	0.978	0.997	32.212
de->de	9.19	21	0.209	0.728	0.961	0.994	31.694
fr->fr	12.03	27.5	0.289	0.754	0.937	0.994	29.376
es->es	14	30.2	0.313	0.766	0.918	0.995	29.539
zh->zh	14.97	30	-	0.687	0.984	0.576	27.228
SG	M-BERT	en->en	15.88	39	0.182	0.873	0.827	0.989	21.642
de->de	8.21	25.2	0.204	0.716	0.822	0.987	25.818
fr->fr	8.89	28.9	0.267	0.73	0.786	0.985	22.296
es->es	10.42	32.3	0.276	0.742	0.765	0.983	20.451
zh->zh	11.38	35.7	-	0.692	0.877	0.839	19.884
XLM	en->en	16.05	38	0.193	0.877	0.763	0.952	22.182
de->de	7.82	29	0.187	0.712	0.785	0.934	21.8
fr->fr	11.24	34.9	0.286	0.747	0.746	0.937	20.087
es->es	11.06	35	0.273	0.742	0.726	0.939	20.473
zh->zh	12.98	36.8	-	0.698	0.842	0.902	19.306
mBART	en->en	17.64	39.8	0.196	0.875	0.827	0.993	22.912
de->de	9.46	26.3	0.222	0.714	0.816	0.99	24.926
fr->fr	12.2	32	0.309	0.741	0.783	0.987	22.549
es->es	13.5	33.8	0.301	0.745	0.752	0.986	20.927
zh->zh	11.16	32.7	-	0.675	0.836	0.982	20.146
mT5	en->en	8.59	33.9	0.13	0.876	0.882	0.982	24.324
de->de	4.05	21.4	0.132	0.698	0.874	0.974	22.8
fr->fr	4.09	25.1	0.176	0.723	0.862	0.977	21.068
es->es	5.39	27.7	0.211	0.727	0.83	0.978	19.884
zh->zh	8.33	31.8	-	0.679	0.901	0.96	21.054