Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!linac!att!ucbvax!fred.UUCP!shc From: shc@fred.UUCP (Steve Couturie) Newsgroups: comp.sys.sgi Subject: Re: Weird Fortran i/o? Message-ID: <9105040132.AA10813@fred> Date: 4 May 91 01:32:55 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 93 Well,: Re: Mail from Ian Graham -- Re weird Fortran I/O times on IRIS 4D/25: > > START-TIME 0.0100 0.0700 > IO WRITE 8.9400 4.7600 > IO READ 26.4600 353.0300 <<---!!!!!! > where the columns are user time and system time, respectively: I tried the test code, and sure enough, it's weird. BUT: a small modification makes it perform very well indeed: Replace the REWIND with CLOSE. Here are timings for 4 machines: [376]fred:shc/junk> ./quickc # 4D/20G, 16M mem, BUSY START-TIME 0.00 0.05 IO WRITE 8.97 1.08 IO READ 13.02 1.42 [21]dino:/tmp> ./quickc # 4D/25TG, 64M mem, idle START-TIME 0.00 0.03 IO WRITE 5.09 0.58 IO READ 7.62 0.88 [25]bambam:/tmp> ./quickc # 4D/240GTX, 56M mem, idle START-TIME 0.00 0.02 IO WRITE 3.66 0.39 IO READ 5.63 0.28 [103]lhdsy1:shc/junk> ./quickc # DEC 5400 Server, 64M mem, ? START-TIME 0.01 0.04 IO WRITE 13.69 74.98 IO READ 7.53 2.24 A 4D/25 runs a bit slower (20 MHz vs. 25 MHz) CPU than does the 5400 or 4D/240, while the 4D/20 is at 12.5 MHz. The 20 and 25 are using SCSI disks; the 240 is using ESDI's; the 5400 is using SCSI (I think). The 20 and 240 are at IRIX 3.3.2, the 25 at IRIX 3.3.1, the 5400 at Ultrix 4.1. I can only surmise that the IRIX Fortran I/O library is not, well, perfect. ---------------------- :-) I also note that the READ's still take a bit longer on the IRISes than the writes; note that the system time has all but vanished, though. Seems like a bug to me. I'd be interested in any comments from the SGI/Mtn.View folks.... ***************************************************************************** Below is the modified code: PROGRAM QUICKC C Date: Fri, 03 May 91 12:56:28 EDT C From: "Dave Gilkinson, hero at large 398-6511 " C C Modified by Steve Couturie, COFRC. REAL TARRAY(2) A= DTIME(TARRAY) WRITE(6,100)TARRAY(1),TARRAY(2) 100 FORMAT(' START-TIME ',F10.2,2X,F10.2) DO I = 1, 100000 WRITE(99) I,I+1,I+2,I+3 ENDDO B = DTIME(TARRAY) WRITE(6,130)TARRAY(1),TARRAY(2) 130 FORMAT(' IO WRITE ', F10.2,2X,F10.2 ) C REWIND(99) CLOSE(99) DO I = 1, 100000 READ(99)K,L,M,N ENDDO B = DTIME(TARRAY) WRITE(6,140)TARRAY(1),TARRAY(2) 140 FORMAT(' IO READ ', F10.2,2X,F10.2 ) STOP END ****************************************************************************** -- Steve Couturie Voice: (213) 694-9332 Chevron Oil Field Research Co. FAX: (213) 694-7228 P.O. Box 446 Internet: shc@chevron.com La Habra, CA 90633-0446 UUCP: ...!uunet!lhdsy1!shc