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From: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu (William Thomas Wolfe, 2847 )
Newsgroups: comp.lang.misc,comp.lang.ada
Subject: Re: Compilation bottlenecks
Message-ID: <8489@hubcap.clemson.edu>
Date: 25 Mar 90 00:45:31 GMT
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>From jamiller@hpcupt1.HP.COM (Jim Miller):
> I know of customers which *will not* recompile, due to the
> impact on the time their operation -- one just better find a better way.
> They are not using C.
>     jim - i'm not even sure these are my opinions - miller

 Although this statement _seems_ to imply that the reason has 
 something to do with the computational complexity of compiling 
 a language in which there is considerably more compiler analysis 
 being done (such as Ada, in which very large projects have often
 taken precisely this approach), in fact the REAL (tm) reason is that...

  MOST ADA COMPILATIONS ARE LIMITED BY I/O CAPACITY, NOT BY CPU SPEED!!!

 I heard at a conference recently of one project for which the time
 required to recompile a very large software system went from around
 ten days to around two or three days, simply by installing enough 
 I/O channel capacity to overcome the I/O bottleneck!!

 Ada is doing a lot of work with the program library's database in order
 to keep track of the relationships among the various compilation units,
 which is very useful in terms of tracking dependencies and is exactly 
 as it should be.  But it gives Ada compilation the basic characteristics
 of any database-oriented application, and having the appropriate hardware
 (such as the tremendous I/O capacity of typical IBM platforms) seems to be
 the single most important key to overcoming this situation, and giving back 
 to the very large projects their ability to recompile over the weekend!
  

 Bill Wolfe, wtwolfe@hubcap.clemson.edu