Re: [9fans] mk time-check/slice issue

[erik quanstrom <quanstro@quanstro.net>]

On Thu Dec 19 05:02:50 EST 2013, 9fans@hamnavoe.com wrote:
> > So, I think you are saying, that for pieces in a mkfile that take less than
> > 1s to build it is possible for them to be build again, unnecessarily, when
> > mk is run again.  This is normal and just the way it is.  Is that correct?
>
> Correct except for "just the way it is".  There is a principle
> involved which is so pervasive to Plan 9 that we often forget to make
> it explicit.  To quote Ken Thompson: "Throughout, simplicity has been
> substituted for efficiency.  Complex algorithms are used only if their
> complexity can be localized."  He was writing in 1978 about UNIX, but
> Plan 9 follows firmly in this tradition.  (Linux not so much.)
>
> Using the existing file time stamps costs some efficiency, when
> targets are built more often than necessary.  The question is, how
> significant is this cost compared to the complexity of adding higher
> time resolution?  Note that it's not necessary to run mk repeatedly
> until it converges -- the algorithm is conservative in the sense that
> it will not build less than required.
>
> So, how many seconds is the unnecessary building of targets actually
> costing?

+1.  i just love to hear this approach expressed better than i can.
sorry for my redundant post.

- erik