Add c++ 20 peformances for gcc9

Performances/G++/perf_saxpy_par_O0.txt

+1000	138.282	138282	2.6397	2639.7
+2000	78.6417	157283	1.38539	2770.78
+3000	56.1991	168597	1.11649	3349.47
+4000	44.8225	179290	0.792006	3168.02
+5000	38.0223	190112	0.525377	2626.89
+10000	23.9285	239285	0.347204	3472.04
+50000	10.7408	537039	0.158685	7934.26
+100000	8.86104	886104	0.126713	12671.3
+200000	7.88914	1.57783e+06	0.134577	26915.3
+500000	7.29708	3.64854e+06	0.142357	71178.5
+1000000	7.12002	7.12002e+06	0.103616	103616
+5000000	6.8786	3.4393e+07	0.0207683	103842
+10000000	6.82782	6.82782e+07	0.00994502	99450.2

Performances/G++/perf_saxpy_par_O1.txt

+1000	30.2078	30207.8	0.372012	372.012
+2000	15.6737	31347.3	0.220571	441.142
+3000	10.8271	32481.3	0.144002	432.006
+4000	8.47274	33891	0.124622	498.487
+5000	6.99484	34974.2	0.0837234	418.617
+10000	4.11972	41197.2	0.0526353	526.353
+50000	1.72626	86312.8	0.0237515	1187.57
+100000	1.36354	136354	0.0174906	1749.06
+200000	1.16658	233315	0.0188796	3775.93
+500000	1.03882	519408	0.0100738	5036.92
+1000000	1.01392	1.01392e+06	0.0150347	15034.7
+5000000	0.958487	4.79244e+06	0.0127153	63576.6
+10000000	0.957556	9.57556e+06	0.00433025	43302.5

Performances/G++/perf_saxpy_par_O2.txt

+1000	33.1435	33143.5	2.80076	2800.76
+2000	15.7297	31459.3	0.225612	451.223
+3000	10.8643	32593	0.164196	492.589
+4000	8.39218	33568.7	0.135887	543.549
+5000	6.91318	34565.9	0.0993696	496.848
+10000	3.85393	38539.3	0.058435	584.35
+50000	1.42856	71427.9	0.0241319	1206.59
+100000	1.04976	104976	0.0190012	1900.12
+200000	0.838413	167683	0.0118471	2369.41
+500000	0.699814	349907	0.00987101	4935.5
+1000000	0.674174	674174	0.0194379	19437.9
+5000000	0.77356	3.8678e+06	0.0143413	71706.4
+10000000	0.807566	8.07566e+06	0.00590961	59096.1

Performances/G++/perf_saxpy_par_O3.txt

+1000	31.2974	31297.4	0.63714	637.14
+2000	15.7802	31560.3	0.233923	467.846
+3000	10.9301	32790.2	0.189401	568.204
+4000	8.09911	32396.5	0.135013	540.052
+5000	6.63696	33184.8	0.108118	540.588
+10000	3.41476	34147.6	0.0493276	493.276
+50000	0.935826	46791.3	0.0142022	710.109
+100000	0.624806	62480.6	0.0102301	1023.01
+200000	0.464701	92940.3	0.00844208	1688.42
+500000	0.368668	184334	0.00651105	3255.52
+1000000	0.480537	480537	0.0124732	12473.2
+5000000	0.788791	3.94395e+06	0.012677	63385
+10000000	0.828985	8.28985e+06	0.00513111	51311.1

Performances/G++/perf_saxpy_par_Ofast.txt

+1000	30.9779	30977.9	0.524068	524.068
+2000	15.7443	31488.6	0.279474	558.949
+3000	10.7643	32293	0.142844	428.532
+4000	8.02044	32081.8	0.109829	439.318
+5000	6.67899	33395	0.18269	913.45
+10000	3.7037	37037	0.118422	1184.22
+50000	0.94992	47496	0.0243845	1219.23
+100000	0.623539	62353.9	0.0101998	1019.98
+200000	0.462801	92560.1	0.00664097	1328.19
+500000	0.371013	185506	0.00694805	3474.02
+1000000	0.473698	473698	0.0107518	10751.8
+5000000	0.789471	3.94736e+06	0.0119175	59587.7
+10000000	0.828005	8.28005e+06	0.00452848	45284.8

Performances/G++/perf_saxpy_par_vectorize_O3.txt

+1000	31.6076	31607.6	0.520755	520.755
+2000	16.4227	32845.4	0.232303	464.607
+3000	11.442	34326.1	0.192078	576.234
+4000	8.30643	33225.7	0.130922	523.688
+5000	6.6978	33489	0.10532	526.599
+10000	3.49241	34924.1	0.0659783	659.783
+50000	0.878774	43938.7	0.0141997	709.984
+100000	0.57824	57824	0.0100202	1002.02
+200000	0.422515	84503.1	0.00822199	1644.4
+500000	0.336273	168136	0.00751786	3758.93
+1000000	0.463679	463679	0.0111846	11184.6
+5000000	0.79318	3.9659e+06	0.0114064	57031.9
+10000000	0.830503	8.30503e+06	0.0055676	55676

Performances/G++/perf_saxpy_par_vectorize_Ofast.txt

+1000	31.7228	31722.8	0.560808	560.808
+2000	16.5836	33167.1	0.379881	759.762
+3000	11.5508	34652.4	0.247846	743.539
+4000	8.28012	33120.5	0.138415	553.661
+5000	6.69106	33455.3	0.101695	508.475
+10000	3.50037	35003.7	0.0656202	656.202
+50000	0.884956	44247.8	0.0136701	683.504
+100000	0.578784	57878.4	0.00976275	976.275
+200000	0.421391	84278.2	0.00792256	1584.51
+500000	0.34089	170445	0.00719762	3598.81
+1000000	0.466146	466146	0.0122164	12216.4
+5000000	0.791052	3.95526e+06	0.0106574	53286.8
+10000000	0.831739	8.31739e+06	0.00535924	53592.4

Performances/G++/perf_saxpy_seq_O0.txt

+1000	31.0692	31069.2	0.237404	237.404
+2000	30.8258	61651.6	0.0967874	193.575
+3000	31.1618	93485.5	0.620297	1860.89
+4000	30.9575	123830	0.085602	342.408
+5000	30.9175	154587	0.109412	547.058
+10000	30.9861	309861	0.0918998	918.998

Performances/G++/perf_saxpy_seq_O1.txt

+1000	1.92811	1928.11	0.00551931	5.51931
+2000	1.91652	3833.04	0.0107183	21.4366
+3000	1.93138	5794.13	0.00910047	27.3014
+4000	1.95287	7811.47	0.00696265	27.8506
+5000	1.97442	9872.1	0.0157495	78.7476
+10000	1.94163	19416.3	0.00384618	38.4618

Performances/G++/perf_saxpy_seq_O2.txt

+1000	1.92671	1926.71	0.0132249	13.2249
+2000	1.90949	3818.98	0.00786719	15.7344
+3000	1.96818	5904.54	0.00563685	16.9106
+4000	1.94708	7788.31	0.0200178	80.0712
+5000	1.97533	9876.64	0.00542876	27.1438
+10000	1.93861	19386.1	0.00483432	48.3432

Performances/G++/perf_saxpy_seq_O3.txt

+1000	0.768961	768.961	0.00252754	2.52754
+2000	0.655782	1311.56	0.00806985	16.1397
+3000	0.715166	2145.5	0.00213651	6.40954
+4000	0.744244	2976.98	0.00301392	12.0557
+5000	0.745601	3728.01	0.00598803	29.9402
+10000	0.769905	7699.05	0.00585687	58.5687

Performances/G++/perf_saxpy_seq_Ofast.txt

+1000	0.772232	772.232	0.00243462	2.43462
+2000	0.657448	1314.9	0.00465279	9.30558
+3000	0.711802	2135.4	0.00326249	9.78748
+4000	0.751613	3006.45	0.0106833	42.7334
+5000	0.749425	3747.13	0.0100352	50.176
+10000	0.74416	7441.6	0.00312091	31.2091

Performances/G++/perf_saxpy_seq_vectorize_O3.txt

+1000	0.339141	339.141	0.00139924	1.39924
+2000	0.258881	517.761	0.000619556	1.23911
+3000	0.440513	1321.54	0.00980635	29.4191
+4000	0.515466	2061.86	0.0153159	61.2636
+5000	0.504587	2522.94	0.0116232	58.1158
+10000	0.526764	5267.64	0.0102976	102.976

Performances/G++/perf_saxpy_seq_vectorize_Ofast.txt

+1000	0.337203	337.203	0.0012097	1.2097
+2000	0.258711	517.421	0.000697245	1.39449
+3000	0.451438	1354.31	0.0116805	35.0415
+4000	0.506964	2027.86	0.0181098	72.4392
+5000	0.519701	2598.5	0.0145246	72.6229
+10000	0.553554	5535.54	0.0108512	108.512

Performances/G++/saxpy_parBase.gnuplot

+set terminal png notransparent crop enhanced size 800,600 font "arial,14"
+set grid xtics ytics mytics
+set key out vert center top
+set logscale x
+set logscale y
+set xlabel "nb elements"
+set ylabel "elapsed time per element [ns/el]"
+set output "saxpy_parBaseElapsedTimeCyEl.png"
+plot "perf_saxpy_par_O0.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par O0" with yerrorlines lw 2,"perf_saxpy_par_O1.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par O1" with yerrorlines lw 2,"perf_saxpy_par_O2.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par O2" with yerrorlines lw 2,"perf_saxpy_par_O3.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par O3" with yerrorlines lw 2,"perf_saxpy_par_Ofast.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par Ofast" with yerrorlines lw 2,
+set xlabel "nb elements"
+set ylabel "elapsed time [ns]"
+set output "saxpy_parBaseElapsedTime.png"
+plot "perf_saxpy_par_O0.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par O0" with yerrorlines lw 2,"perf_saxpy_par_O1.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par O1" with yerrorlines lw 2,"perf_saxpy_par_O2.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par O2" with yerrorlines lw 2,"perf_saxpy_par_O3.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par O3" with yerrorlines lw 2,"perf_saxpy_par_Ofast.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par Ofast" with yerrorlines lw 2,

Performances/G++/saxpy_parVectorize.gnuplot

+set terminal png notransparent crop enhanced size 800,600 font "arial,14"
+set grid xtics ytics mytics
+set key out vert center top
+set logscale x
+set logscale y
+set xlabel "nb elements"
+set ylabel "elapsed time per element [ns/el]"
+set output "saxpy_parVectorizeElapsedTimeCyEl.png"
+plot "perf_saxpy_par_O3.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par O3" with yerrorlines lw 2,"perf_saxpy_par_vectorize_O3.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par vectorize O3" with yerrorlines lw 2,"perf_saxpy_par_vectorize_Ofast.txt" using 1:2:($2-$4):($2+$4) title "perf saxpy par vectorize Ofast" with yerrorlines lw 2,
+set xlabel "nb elements"
+set ylabel "elapsed time [ns]"
+set output "saxpy_parVectorizeElapsedTime.png"
+plot "perf_saxpy_par_O3.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par O3" with yerrorlines lw 2,"perf_saxpy_par_vectorize_O3.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par vectorize O3" with yerrorlines lw 2,"perf_saxpy_par_vectorize_Ofast.txt" using 1:3:($3-$5):($3+$5) title "perf saxpy par vectorize Ofast" with yerrorlines lw 2,