Table 5.

Comparison of the NDCG at 10 of the layout selected according to the two proposed greedy strategies and compared to the exhaustive search of all possible model selections and rankings.

		Number of carousels
		2	3	4	5	6	7	8
Movielens 20M (M = 16)
Solution space size	Number of rankings	2.4 · 102	3.3 · 103	4.3 · 104	5.2 · 105	5.7 · 106	5.7 · 107	5.1 · 108
	Number of selections	1.2 · 102	5.6 · 102	1.8 · 103	4.3 · 103	8.0 · 103	1.1 · 104	1.2 · 104
Selection method	Exhaustive selection and ranking	0.3168	0.3220	-	-	-	-	-
	Exhaustive selection default ranking	0.3168	0.3220	0.3266	0.3296	-	-	-
	Incremental greedy	0.3168	0.3220	0.3266	0.3297	0.3320	0.3345	0.3363
	Individual greedy	0.3168	0.3180	0.3190	0.3241	0.3250	0.3295	0.3309
Netflix Prize (M = 14)
Solution space size	Number of rankings	1.8 · 102	2.1 · 103	2.4 · 104	2.4 · 105	2.1 · 106	1.7 · 107	1.2 · 108
	Number of selections	9.1 · 101	3.6 · 102	1.0 · 103	2.0 · 103	3.0 · 103	3.4 · 103	3.0 · 103
Selection method	Exhaustive selection and ranking	0.2781	-	-	-	-	-	-
	Exhaustive selection default ranking	0.2781	0.2809	-	-	-	-	-
	Incremental greedy	0.2781	0.2812	0.2830	0.2865	0.2891	0.2912	0.2931
	Individual greedy	0.2692	0.2701	0.2689	0.2714	0.2740	0.2761	0.2777
ContentWise impressions (M = 12)
Solution space size	Number of rankings	1.3 · 102	1.3 · 103	1.1 · 104	9.5 · 104	6.6 · 105	3.9 · 106	2.0 · 107
	Number of selections	6.6 · 101	2.2 · 102	4.9 · 102	7.9 · 102	9.2 · 102	7.9 · 102	4.9 · 102
Selection method	Exhaustive selection and ranking	0.5162	0.5099	0.5133	0.5153	-	-	-
	Exhaustive selection default ranking	0.5162	0.5099	0.5132	0.5152	0.5178	0.5199	0.5213
	Incremental greedy	0.5162	0.5099	0.5133	0.5153	0.5179	0.5201	0.5215
	Individual greedy	0.5162	0.5098	0.5123	0.5149	0.5172	0.5183	0.5190

The page layout contains from 2 to 8 carousels. Results for exhaustive searches requiring more than a week of computation are missing.