Long compile time

[David Arnold <darnold@northcoast.com>]

All,

For me, the most frustrating thing about ConTeXt seems to be the long time
it takes to compile. I've read the texexex.pdf file and there are some nice
hints in there to reduce the compile time. I still have two questions.

1. Can I reduce to a minimum the compile time by entering a comment in the
first line of my file, something akin to

%output=pdf

that I use frequently? If this can be done, what is an optimal comment line
for limiting the compile time?

2. Suppose I have a master document with 

\input chap1
\input chap2
\input chap3

etc. Suppose I am working in chap3.tex and I only want to compile chap3. Of
course, I can comment out 

%\input chap1
%\input chap2

but then I lose the correct numbering of pages, chapters, etc. Is there a
better procedure?