Path: utzoo!utgpu!watmath!att!rutgers!ucsd!usc!cs.utexas.edu!uunet!ncrlnk!ncrcae!hubcap!ut-emx!gary From: ut-emx!gary@cs.utexas.edu (Gary Smith) Newsgroups: comp.parallel Subject: Re: Information on Massively parallel machines Message-ID: <7070@hubcap.clemson.edu> Date: 16 Nov 89 13:21:34 GMT Sender: fpst@hubcap.clemson.edu Lines: 133 Approved: parallel@hubcap.clemson.edu In article <7041@hubcap.clemson.edu>, SAROFF@BNLDAG.AGS.BNL.GOV writes: > I am interested in getting information, technical specs, software > available, personal experiences, benchmarks, that sort of thing about > the massively parallel machines currently available. > > If some of you have opinions or ideas about > > NCUBE > Thinking Machine > Kendall Square > Evans and Sutherland > MassPar > Key Computers > (or Others . . .) > > I would appreciate hearing. > > Thanks Muchly > > Stephen Saroff > I must admit I remain very skeptical that massive MIMD parallelism will pay off in the near future, if ever. Now modest MIMD parallelism, up to perhaps 256 processors might, assuming we get a significant number of applications that can achieve parallelism in excess of 99.9%, and if syn- chronization overhead can be made arbitrarily small. Of course, these are pretty severe constraints! The matrix below is the reason for my skepticism. I included the short C program I used to generate the F's. Gary Smith UT System CHPC Balcones Research Center 10100 Burnet Rd Austin, TX 78758-4497 Internet: g.smith@chpc.utexas.edu ========================================================================== Maximum Speedup Assuming Zero Overhead -------------------------------------- Speedup = F(f,p) = 1/[(1-f)+(f/p)] f: fraction of code parallelized p: number of processors employed f \ p 8 16 32 64 128 256 512 1024 2048 4096 8192 16K 32K 65K --------------------------------------------------------------------------- 10.00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 15.00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 20.00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 25.00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 30.00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 35.00 1 1 2 2 2 2 2 2 2 2 2 2 2 2 40.00 2 2 2 2 2 2 2 2 2 2 2 2 2 2 45.00 2 2 2 2 2 2 2 2 2 2 2 2 2 2 50.00 2 2 2 2 2 2 2 2 2 2 2 2 2 2 55.00 2 2 2 2 2 2 2 2 2 2 2 2 2 2 60.00 2 2 2 2 2 2 2 2 2 2 2 2 2 2 65.00 2 3 3 3 3 3 3 3 3 3 3 3 3 3 70.00 3 3 3 3 3 3 3 3 3 3 3 3 3 3 75.00 3 3 4 4 4 4 4 4 4 4 4 4 4 4 80.00 3 4 4 5 5 5 5 5 5 5 5 5 5 5 85.00 4 5 6 6 6 7 7 7 7 7 7 7 7 7 90.00 5 6 8 9 9 10 10 10 10 10 10 10 10 10 90.50 5 7 8 9 10 10 10 10 10 11 11 11 11 11 91.00 5 7 8 10 10 11 11 11 11 11 11 11 11 11 91.50 5 7 9 10 11 11 12 12 12 12 12 12 12 12 92.00 5 7 9 11 11 12 12 12 12 12 12 12 12 12 92.50 5 8 10 11 12 13 13 13 13 13 13 13 13 13 93.00 5 8 10 12 13 14 14 14 14 14 14 14 14 14 93.50 5 8 11 13 14 15 15 15 15 15 15 15 15 15 94.00 6 8 11 13 15 16 16 16 17 17 17 17 17 17 94.50 6 9 12 14 16 17 18 18 18 18 18 18 18 18 95.00 6 9 13 15 17 19 19 20 20 20 20 20 20 20 95.50 6 10 13 17 19 21 21 22 22 22 22 22 22 22 96.00 6 10 14 18 21 23 24 24 25 25 25 25 25 25 96.50 6 10 15 20 24 26 27 28 28 28 28 29 29 29 97.00 7 11 17 22 27 30 31 32 33 33 33 33 33 33 97.50 7 12 18 25 31 35 37 39 39 40 40 40 40 40 98.00 7 12 20 28 36 42 46 48 49 49 50 50 50 50 98.50 7 13 22 33 44 53 59 63 65 66 66 66 67 67 99.00 7 14 24 39 56 72 84 91 95 98 99 99 100 100 99.10 8 14 25 41 60 78 91 100 105 108 110 110 111 111 99.20 8 14 26 43 63 84 101 111 118 121 123 124 125 125 99.30 8 14 26 44 68 92 112 125 134 138 140 142 142 143 99.40 8 15 27 46 73 101 126 143 154 160 163 165 166 166 99.50 8 15 28 49 78 113 144 167 182 191 195 198 199 199 99.60 8 15 28 51 85 127 168 201 223 236 243 246 248 249 99.70 8 15 29 54 93 145 202 252 287 308 320 327 330 332 99.80 8 16 30 57 102 170 253 336 402 446 471 485 493 496 99.90 8 16 31 60 114 204 339 506 672 804 891 943 970 985 99.91 8 16 31 61 115 208 351 533 721 874 979 1041 1075 1093 99.92 8 16 31 61 116 213 363 563 776 958 1085 1161 1204 1227 99.93 8 16 31 61 118 217 377 597 842 1059 1217 1314 1369 1398 99.94 8 16 31 62 119 222 392 635 919 1185 1385 1513 1586 1625 99.95 8 16 32 62 120 227 408 677 1012 1344 1608 1783 1885 1941 99.96 8 16 32 62 122 232 425 727 1126 1553 1916 2169 2323 2408 99.97 8 16 32 63 123 238 444 784 1269 1838 2369 2770 3026 3172 99.98 8 16 32 63 125 244 465 850 1453 2252 3105 3831 4338 4646 99.99 8 16 32 64 126 250 487 929 1700 2906 4503 6210 7662 8676 =========================================================================== main() { double f; for(f=1000.0; f!=9000.0; f+=500.0) speedup(f); for(f=9000.0; f!=9900.0; f+=50.0) speedup(f); for(f=9900.0; f!=9990.0; f+=10.0) speedup(f); for(f=9990.0; f!=10000.0; f+=1.0) speedup(f); } speedup(f) double f; { double p; printf("%5.2f",f*0.01); for(p=8.0; p<131072.0; p+=p) printf("%5.0f",10000.0/((10000.0-f)+(f/p))); printf("\n"); return(0); }