Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!rutgers!mcnc!ece-csc!ncrcae!ncr-sd!hp-sdd!hplabs!ucbvax!VENUS.YCC.YALE.EDU!leichter
From: leichter@VENUS.YCC.YALE.EDU ("Jerry Leichter")
Newsgroups: comp.os.vms
Subject: re: run myprog/topcpu=?  Clarification
Message-ID: <8710171835.AA08060@ucbvax.Berkeley.EDU>
Date: Sat, 17-Oct-87 11:33:00 EDT
Article-I.D.: ucbvax.8710171835.AA08060
Posted: Sat Oct 17 11:33:00 1987
Date-Received: Sun, 18-Oct-87 12:37:45 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: "Jerry Leichter" <leichter@venus.ycc.yale.edu>
Organization: The ARPA Internet
Lines: 51


	...I would like to be able to do is say $ RUN MYPROGRAM/TOPCPU=50:30
	for example, so that myprogram will only run for 50 minutes, 30
	seconds of cpu. The time does not have to be dead on, anything
	reasonable close would be ok....

As you note later, there is no built-in way to do this.  The best approach,
if you can modify the program, is to let it time itself:  Use SYS$SETIMR to
request an AST after some appropriate period of time.  In the AST routine,
check the accumulated runtime of the image (SYS$GETJPI will get it for you)
and either re-schedule the AST or do a SYS$EXIT().  Using a fixed value of,
say, 10 seconds for "appropriate" should work; the clever way is to wait for
an amount of real time that equals the amount of further CPU time you want
the image to have.

The system calls involved here are fairly simple, but you can make things
even easier on yourself by using VAX C - alarm() sets an alarm clock that you
can catch with a signal handler; times() returns CPU time.  You can use
these even if your program is not written in C, though to use the signal
stuff you would have to have a C main program.  (Well, maybe not with the
VMS V4.6 version of the C RTL.)

Of course, the clean way to do this is to have a generic "establish time
limit" procedure that you could put in a library and have all your code call.

If you can't or don't want to modify your code, there's a simpler approach:
Run the image in a subprocess, and monitor it from the main process.  The
following (untested!) draft of a command file should do it:

$!
$! Invoke as:  @MRUN <time> <image> ...
$!
$! Where time is given if seconds.
$!
$ maxseconds = p1		!Be fancy here for, say, MM:SS times
$ maxtime = maxseconds * 100	!(CPU time is measured in 10ms units
$ spawn/nowait/process:"Watched_Pot" run 'p2' 'p3' 'p4' 'p5' 'p6' 'p7' 'p8'
$loop:
$ wait 00:00:10			!You can be fancy here
$ cputime = f$getjpi("Watched_Pot","CPUTIM")
$ if (cputime .lt. maxtime) then goto loop
$ stop "Watched_Pot"

This will forcibly clobber the process when it runs out of time.  It's
possible to do things like force it to exit (SYS$FORCEX call) - there's no
standard DCL interface to that call, but interface programs have been
written many times.  Or you could just suspend the image, waiting for some
human to look at it to decide if it should really be stopped or not.

							-- Jerry
------