billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu (William Thomas Wolfe, 2847 ) (03/25/90)
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