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From: mdash@sfsup.UUCP
Newsgroups: comp.lang.ada
Subject: Re: Problems with creating large number of tasks that utilize re-entrant code
Message-ID: <1179@sfsup.UUCP>
Date: Tue, 10-Mar-87 10:13:08 EST
Article-I.D.: sfsup.1179
Posted: Tue Mar 10 10:13:08 1987
Date-Received: Thu, 12-Mar-87 22:52:05 EST
References: <1859@cwruecmp.UUCP>
Reply-To: mdash@/lang2/mdashUUCP (45415-M.D.Scheer)
Organization: AT&T Information Systems
Summary: access collections are the problem
List-Id: <comp.lang.ada>

In article <1859@cwruecmp.UUCP> asheem@cwruecmp.UUCP (Asheem Chandna) writes:
>
>Hi,
>
>   Thus we represent the STATION entity by a task type and at
>run time the user enters the number of STATIONS. The stations
>are then created dynamically (using access type pointers to the
>STATION task type).
>
>   The problem that we have is that we are unable to create a
>large number of stations. After creating about 70 STATION tasks
>we get "STORAGE ERROR". However, we seem to have sufficient
>virtual memory allocated plus the paging tables etc. all seem
>to be OK. 
>
>Each station has an access type record that contains it's parameters.
>These parameters are updated by calls on several re-entrant procedures.
>
>   I'd appreciate any help I can get. Also any criticisms relating
>to my methodology of using one task per station and using re-entrant 
>calls for the common code.

I can't see that re-entrant code has anything to do with this problem.
All Ada-generated code that does not reference persistent data should be
re-entrant.

According to the technical summary, VAX Ada allocates a sub-heap (access
collection) for each access type.  So the likely source of your problem is
that you are exhausting this pre-allocated space.  The obvious solution is
to allocate a larger access collection using a length clause for the access
type, i.e.,

	for A_TASK_DECLARATIONS'STORAGE_SIZE use ENOUGH_SPACE;

Of course, this will work only if VAX Ada implements length clauses for
access collections; I don't know offhand whether it does.  See LRM 13.2.

Mike Scheer
AT&T Information Systems, Summit NJ
201-522-6196