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Path: utzoo!mnetor!uunet!mcvax!enea!sommar
From: sommar@enea.se (Erland Sommarskog)
Newsgroups: comp.lang.ada
Subject: Generics and disk overhead
Message-ID: <2792@enea.se>
Date: 2 Mar 88 12:51:46 GMT
Reply-To: sommar@enea.UUCP(Erland Sommarskog)
Followup-To: comp.lang.ada
Organization: ENEA DATA AB, Sweden
List-Id: <comp.lang.ada>


The scene: Four generic packages, a list handler(L), a queue and
stack handler(QS), a binary-tree handler(B) and a package for 
topological sorting(T). Some of the procedures in B are also generic.
Add to this a main program (M). Now M instantiates T, which instantiates 
B and QS and also some of the procedures in B. Finally QS instantiates L. 
All packages have a limited type parameter. The size of the code was
around 1100 lines, including comments, in kbytes around 40.

After compilation and linking this expanded to 900 kbytes! I find 
that quite extreme. My environment is VADS 5.41, 4.3 BSD and VAX. 
VADS uses the DIANA format, and these files are also the big 
consumers of disk space, but I have no idea if it is really 
necessary.
  To compare I also compiled and linked the program on VMS with
DEC-Ada. This costed 430 blocks or 220 kbytes. Somewhat more
reasonable. However, DEC does cheat. Recompiling a generic body
invalidates the instantiations. On the other hand recompilation 
with seven reinstantiations took a good time with VADS.

I'm not really sure whether DEC's cheating is permitted or not. The
paragraph in question would be 10.3(7-9). Anyone who knows? But
VADS seems definitely to be doing it wrong. Under some circumstances
the library acts as if a generic body was dependent of its instantiation.
-- 
Erland Sommarskog       
ENEA Data, Stockholm        
sommar@enea.UUCP           "Souvent pour s'amuser les hommes d'equipages
                            and it's like talking to a stranger" -- H&C.