On Tue, Sep 08, 2015 at 07:16:52AM +0000, Guenter Milde wrote:
> On 2015-09-08, Scott Kostyshak wrote:
> > On Mon, Sep 7, 2015 at 9:57 PM, Enrico Forestieri <for...@lyx.org> wrote:
> >> On Mon, Sep 07, 2015 at 04:11:07PM -0400, Scott Kostyshak wrote:
> >>> On Sun, May 03, 2015 at 02:02:06AM +0200, Enrico Forestieri wrote:
> >>> > On Sat, May 02, 2015 at 07:03:53PM -0400, Scott Kostyshak wrote:
>
> >>> My question is, when the user begins a preview, shouldn't the .aux
> >>> always removed so there is a fresh compile?
>
> No.
>
> >>> I think the answer has to do with somehow there is a faster
> >>> compilation if that .aux can be reused.
>
> Yes.
>
> >>> What determines whether the aux should be used or regenerated though?
> >>> LyX or LaTeX?
>
> Aux files are (re)generated with every LaTeX run. Whether they are outdated
> or not is determined by LaTeX based on the content:
>
> * if they are outdated (e.g. new or removed sections, targets on a
> different page, ...) LaTeX will issue the usual "labels may have changed"
> warning, triggering a new LaTeX run.
>
> * if they are still up-to-date, one LaTeX run will suffice to get a document
> with valid cross-links - this is checked automatically by LaTeX after any
> compilation run.
>
> There are cases where you this simple logic may fail:
>
> a) includeonly,
>
> >> There are cases where the previously generated aux files are useful and
> >> removing them causes wrong results. For example, if you include a number
> >> of child documents, say a child for each chapter, like this:
>
> >> \begin{document}
> >> \include{chap1}
> >> \include{chap2}
> >> ...
> >> \end{document}
>
> >> latex generates aux files for each included child. If you later are only
> >> working on chapter 4, you could do
>
> >> \includeonly{chap4}
> >> \begin{document}
> >> \include{chap1}
> >> \include{chap2}
> >> ...
> >> \end{document}
>
> >> and only chap4.tex gets compiled while cross-references to other chapters
> >> are still correct because their aux files are still there.
>
> > And how do we know that the aux files do not need updating? Does this
> > depend on whether the timestamp of the corresponding .tex is newer or
> > older?
>
> There is no timestamp comparison. The \includeonly option is also just for
> speedup during editing/preview. The user is responsible to include files
> that have changed significantly or live with an approximation of the
> document as preview. The final compilation should in any case be done with
> all documents included.
>
>
> b) removal of packages or other definitions from the preamble:
>
> When latexing "per hand", I mostly just leave the *.aux files in the
> folder for late use (which may be after some years...)
>
> Sometimes get an compilation error when removing a language option
> from a document and re-compiling: "language .... not defined".
> This is caused by the *.aux file still containing use cases for this
> language.
>
> The problem usually goes away for the next run (because the aux-file was
> updated).
>
> LyX could trigger removal of *.aux files if the same error occures in two
> successive compilation runs.
Thanks a lot, Günter. This is very helpful!
Scott
