szabo_p@maths.su.oz.au (Paul Szabo) (10/26/90)
In FORTRAN, to write a file you OPEN it and then WRITE to the unit.
Somehow, this generates an inordinate amount of network traffic!
An example:
open (9,file='silly.out',status='new')
do i=1,1000
write (9,99) 'Just saying HELLO ...'
end do
99 format (a)
end
Running this (on a diskless node), using /etc/nodestat to display
network I/O statistics before and after, we see that this program
generates 13515 packets (6871 receive, 6644 transmit). Now this is
something like 12 packets per line, or 12kbytes per each line of 22
bytes, or a 500-fold increase in traffic!
If instead we used WRITE to unit 6, and then used the shell's
redirection (>) to write the file, we would have generated only about
250 packets (including all overheads, even the /etc/nodestat itself).
No problems are seen either if we re-write the program in C (using
fopen and fprintf). But using status='write' or recl=25 in the OPEN
statement seems to have no effect.
Has anyone come across this problem before? Is this a nasty bug, or is
there a simple workaround?
Any insight would be appreciated. We are desperate: imagine a couple
of dozen undergraduate students trying to write some files using
trivial little FORTRAN programs...
Paul Szabo szabo_p@maths.su.oz.aukahlers@ux1.cso.uiuc.edu (10/27/90)
> In FORTRAN, to write a file you OPEN it and then WRITE to the unit. > Somehow, this generates an inordinate amount of network traffic! There is a patch (for SR10.2, I think) which corrects a bad performance problem with the Fortran write library routines. It is a new ftnlib. This patch sure helped our Fortran write performance problems. Do you have this patch installed? -Kem ======================================================================== Kem Ahlers kahlers.ux1.cso.uiuc.edu (Internet) Caterpillar, Inc. u36009@ncsagate (Bitnet) Peoria, IL USA uunet!uiucuxc!uiucux1!kahlers (uucp)