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From: ebert@muc.de (Rolf Ebert)
Subject: scheduler program in Ada
Date: 1998/06/05
Message-ID: <6l97ru$l9@colin.muc.de>#1/1
X-Deja-AN: 359880903
Organization: MUC.DE - Individual Network (IN) Domain Munich
Newsgroups: comp.lang.ada
Date: 1998-06-05T00:00:00+00:00
List-Id: <comp.lang.ada>


I'd like to write a scheduler in Ada much like the Unix crond
program.

The program has a cycle time of 5 minutes, for example.   A config file
specifies jobs which have to be started at a given offset from the 
start of the cycle.  That is I have a list of (offset,job) pairs.
The possible offsets have a resolution of 1/10 sec.  Theoretically
we could start 5*60*10=3000 jobs per 5min. cycle.

What is the best approach to do that in Ada?

I have thought about two possible solutions:
1) One task starts a new task every 1/10 sec. The newly created task
   looks into the (offset,jobs) - list and decides if anything is to do.
   If it is , it starts the corresponding job.  Either the task terminates
   after finishing the job or it stops if there is nothing to do.

2) As the list of (offset,job)-pairs does not change over time, the 
   scheduler can calculate the starting times once for all.  It can than 
   avoid starting unneccessary tasks .

Not having too much experience with the tasking facilities of Ada, is there
anything else I can do?

	Rolf
	ebert@wapor.muc.de
	ebert@muc.de
	ebert@pe-muc.de