Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!linac!att!ucbvax!SMAUG.PHYSICS.MCGILL.CA!igraham
From: igraham@SMAUG.PHYSICS.MCGILL.CA (Ian Graham)
Newsgroups: comp.sys.sgi
Subject: Weird Fortran i/o?
Message-ID: <9105031951.AA02478@smaug.physics.mcgill.ca>
Date: 3 May 91 19:51:25 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 64

Hello,

A user on our system was checking benchmarks for system i/o on 
IRIS/SUN/HP9000/DECSTATION and came up with the following quirky 
results: (THe code is given at the bottom)  THe program writes
100000 bunches of 4 integers into a direct access fie, rewinds, 
and reads 'em all back.   Here are the results for a 4D-25:

START-TIME         0.0100      0.0700
IO WRITE           8.9400      4.7600
IO READ           26.4600    353.0300 <<---!!!!!!

So what gives?  Why should it take 5 MINUTES to read some data written
in 5 SECONDS!   On a Decstation 3000 (same CPU chipset...)  the OPPOSITE 
is true -- it takes 5 minutes to WRITE the file, and only 5 seconds to 
READ it!  On a Sun-3 things are altogether slower, but again the write 
is much slower than the read:

IO WRITE         100.4800    320.0400
IO READ           50.7400      8.1800

Meanwhile  on an HP9000 (Snake!??!) it takes only 5 seconds to 
read and/or write.  Nice if you are heavily i/o bound and running 
Fortran (as is the case for this user.)   

Anyone know what's going on? 

HEre are the system specifics, as far as I know them, and the test code:

IRIS      4D-25,        IRIX 3.3.1
SUN    SUN3-180,        SUNOS3.5
DEC    Decsation 3100,  ??
HP     HP9000-720       ??

                PROGRAM QUICKTEST
C Date: Fri, 03 May 91 12:56:28 EDT
C From: "Dave Gilkinson, hero at large 398-6511 " <gilk@campy>
                REAL TARRAY(2)             
                A= DTIME(TARRAY)
                WRITE(6,100)TARRAY(1),TARRAY(2)
 100            FORMAT(' START-TIME ',F10.4,2X,F10.4)

                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 ', F10.4,2X,F10.4 )
                REWIND(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 ', F10.4,2X,F10.4 )
                STOP
                END            


    ___________________________________________ Ian Graham ______________
						igraham@physics.mcgill.ca
					        Tel: (514) 398-6526
					        Fax: (514) 398-8434