X-Git-Url: https://scripts.mit.edu/gitweb/www/ikiwiki.git/blobdiff_plain/5ca59b3a8db9a804167b0e081c311bd41993781c..711f86e627e56f317d367d1d9a5bd71afb7697df:/doc/bugs/Buggy_dependency_graph.mdwn?ds=sidebyside

diff --git a/doc/bugs/Buggy_dependency_graph.mdwn b/doc/bugs/Buggy_dependency_graph.mdwn
index d90884bb5..116a2aea4 100644
--- a/doc/bugs/Buggy_dependency_graph.mdwn
+++ b/doc/bugs/Buggy_dependency_graph.mdwn
@@ -3,29 +3,27 @@ I think there is a problem in my "dependency graph". As an example,
 ikiwiki generated for [my site](http://poivron.org/~nil/misc/ikiwiki_buggy_index)
 (note that the site changed since this index was generated).
 
-Some **HUGE** dependencies appear, like
+Some **HUGE** dependencies appear, clearly non optimal, like
 
-    depends=((((((....((((((A|B)|A)|C)|A)|D)|A)|E)|A)|F)|A)|G....)
+    depends = A｜ B | A | C | A | D | A | E | A | F | A | G | ....
 
-    depends=((((((....((((((A|B)|C)|D)|A)|B)|C)|D)|A)|B)|C)|A)|B....)
+or 
+
+    depends= A | B | C | D | A | B | C | D | A | B | C | D | ....
 
 Couldn't isolate the cause, but some sources for this problem may be:
 
 * related to the img module
-
-* very visible because one of my pages includes 80 resized images
+* easily observable in my sire because one of my pages includes 80 resized images
 
 Other special things in my templates and site:
 
 * a sidebar with \[[include pages="notes/\*" template=foo]] while notes.mdwn has 
   a \[[include pages="notes/*"]] and uses the sidebar; removed it, doesn't change
-
 * a template (biblio.tmpl) calling the "img" plugin with a template parameter as the
   image filename; removed it, doesn't change
-
 * some strange games with tags whose page calls a "map" directive to show other tags
   shile tags are also used in tagclouds (in the sidebar and in the main pages)
-
 * ...
 
 I observed these problems (same *kind*, I didn't check in details) on
@@ -33,6 +31,50 @@ I observed these problems (same *kind*, I didn't check in details) on
 * ikiwiki 2.00gpa1 + v5.8.4 + Debian 3.1
 * ikiwiki 2.3 + v5.8.8 + Ubuntu 7.04
 
-I can think about stripping down my wiki source and making it available online for analysis.
+I can think about reducung the size of my wiki source and making it available online for analysis.
 
 -- NicolasLimare
+
+> As long as these dependencies don't grow over time (ie, when a page is
+> edited and nothing changed that should add a dependency), I wouldn't
+> worry about them. There are many things that can cause non-optimal
+> dependencies to be recorded. For one thing, if you inline something, ikiwiki
+> creates a dependency like:
+> 
+> (PageSpec) or (file1 or file2 or file3 ...)
+> 
+> Where fileN are all the files that the PageSpec currently matches. (This
+> is ncessary to detect when a currently inlined file is deleted, and know
+> the inlining page needs an update.) Now consider what it does if you have
+> a single page with two inline statements, that inline the same set of
+> stuff twice:
+> 
+> ((PageSpec) or (file1 or file2 or file3 ...) or (PageSpec) or (file1 or file2 or file3 ...)
+>
+> Clearly non-optimal, indeed.
+> 
+> Ikiwiki doesn't bother to simplify complex PageSpecs
+> because it's difficult to do, and because all they use is some disk
+> space. Consider what ikiwiki uses these dependencies for.
+> All it wants to know is: does the PageSpec for this page it's considering
+> rebuilding match any of the pages that have changed? Determining this is
+> a simple operation -- the PageSpec is converted to perl code. The perl
+> code is run.
+> 
+> So the total impact of an ugly dependency like this is:
+> 
+> 1. Some extra data read/written to disk.
+> 2. Some extra space in memory.
+> 3. A bit more data for the PageSpec translation code to handle. But that
+>    code is quite fast.
+> 4. Typically one extra function call when the generated perl code is run.
+>    Ie, when the expression on the left-hand side fails, which typically
+>    happens after one (inexpensive) function call, it has to check
+>    the identical expression on the right hand side.
+> 
+> So this is at best a wishlist todo item, not a bug. A PageSpec simplifier
+> (or improved `pagespec_merge()` function) could be written and improve
+> ikiwiki's memory and disk usage, but would it actually speed it up any?
+> We'd have to see the code to the simplifier to know.
+> 
+> --[[Joey]]