Re: The Dreaded "Missing Subunits"

["Randy Brukardt" <randy@rrsoftware.com>]

Robert A Duff wrote in message ...

>Every time you tell the tool to re-analyze the world, it has to do
this:
>(1) Expand the wildcard(s), to see if there are any new files or any
>files have been deleted.  Then (2) check the timestamp on each source
>file to see if it has been changed.  Then it has to re-parse all the
>files that have changed, or are new (and it has to forget about
>information related to deleted files).  This process is quite fast,
even
>for large programs.  It's essentially what 'make' does when you say
>'make main_program', or what 'gnatmake' does when told to build a
>program.


Careful! Don't assume that these steps are faster than just parsing the
file. When we were (re)designing our make tool, we found that reading a
timestamp took about the same amount of time as parsing 500 lines of a
file (this was on MS-DOS/Windows 95, I think). Moreover, saving the
gathered information on disk was complex enough that it cost the same as
parsing another 1000 lines of a file. Not many Ada files are bigger than
1500 lines. So we don't even try to save information about source files;
reparsing and rebuilding the information in memory is generally faster.

This is essentially the basis of Xtreme Programming, after all: don't
build something complex until you've proven that the simple version is
too slow. (Just another piece of common sense that someone is making a
lot of money selling to people without it.)

         Randy Brukardt