#500000		sparse				full			#50000		sparse				full					
#nb threads	times		nb iter		times		nb iter			times		nb iter		times       nb iter		
1024		523		27 		1407.24		29   			4.28372 	18   		8.61	    16
512		449.426 	24		1459.35		31			4.28551		18		9.27	    19
256             440.805 	24		754.24		27			4.13975		18		7.73	    15
128		456.175 	22		718.623		27			4.15309		18		8.64	    21
64		472.862 	23		715.554		27			3.92233 	17		7.84	    16
32		830.152		24		1089.61		27			6.70821		21		11.33	    18
16		1234		24		1746.53		22			12.3981		21		20.47	    21
8		2632.78		23 		3112		20			 23.813		21		35.07	    26