Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site noao.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!princeton!astrovax!noao!allan From: allan@noao.UUCP Newsgroups: net.physics Subject: VMS vs. Unix (timings) Message-ID: <359@noao.UUCP> Date: Fri, 22-Jun-84 14:09:54 EDT Article-I.D.: noao.359 Posted: Fri Jun 22 14:09:54 1984 Date-Received: Sat, 23-Jun-84 04:15:00 EDT Organization: Natl. Optical Astronomy Obs. Tucson AZ USA Lines: 71 Prompted by all the discussion on fortran vs. C and VMS vs. unix, I have run some comparison programs and timed the results. I have run a 100 x 100 matrix multiplication program in fortran (single precision and double precision) and C on VMS, 4.1 and 4.2 unix. The cpu run times in seconds are shown below. I will post the program listings separately for those who wish to pull them apart. fortran(sp) fortran(dp) C vax1 no opt 69 112 102 vax1 opt 52 98 99 vax2 no opt 40 51 63 vax2 opt 40 49 64 vax3 no opt 32 43 48 vax3 opt 22 35 31 Key: vax1 = 4.2BSD Unix#8 vax2 = Berkeley VAX/UNIX 4.1 + floating point accelerator vax3 = VMS 3.6 + floating point accelerator opt = optimization turned on As far as VMS vs. unix is concerned, VMS is faster than 4.1 unix by a factor of 1.5 on average. 4.2 unix is slower than 4.1 simply because that machine does not have a floating point accelerator. Comparing the languages, single precision fortran is faster than C by a factor of 1.6 on average, and there is barely any difference between double precision fortran and C on the average. The single comparison that is usually made is fortran on VMS vs. C on unix. In this case fortran is faster by a factor of 3 using 4.1 unix. You can argue anyway that you like from these numbers. Single precision fortran is obviously fastest, but it is fairer to compare double precision fortran and C since C does all floating point operations in double precision, but fortran will let you use single precision when you want to where as C will not, but, but, but, .......... ....... .... .. . . . I am not prepared to defend fortran on the grounds of the 'niceness' of the language. For some applications, fortran stinks. However, one thing does seem clear. IF the bottom line is speed of execution THEN you should use fortran on VMS All the above has been concerned with vaxes. If you really need the greatest speed, then you must go out and buy a Cray or a CDC205. If you want to pull all of this apart by arguing that you should not generalize from a single experiment then I suggest that you run some experiments of your own. Peter Allan Kitt Peak National Observatory Tucson, Az UUCP: {akgua,allegra,arizona,decvax,hao,ihnp4,lbl-csam,seismo}!noao!allan ARPA: noao!allan@lbl-csam.arpa