[Texmacs-dev] Revised patch: Speedup in startup time

[Norbert Nemec]

Sorry about that. Here is a patch that should solve the issue more 
safely by using local static variables that are are initialized at the 
first call to the routine.

Unfortunately, this adds the overhead of checking a flag at each call, 
but it is the simplest solution and still significantly faster than the 
allocation of a new object at each call.

Greetings,
Norbert


Gubinelli Massimiliano wrote:
> Hi all,
>  the patch for is_none (url) does not work correcly. In C++ the order 
> of nonlocal static initializations is undefined, so it can happen (at 
> least to me) that
> none_tree is not itialized when url_none is called.... This causes a 
> Bus error on mac.
> Please remove the patch or provide explicit initialization on first 
> use. See for example
>
>
> http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Runtime_Static_Initialization_Order_Idioms 
>
>
>
> Best,
> Max
>
>
>
> On 14 juin 09, at 03:59, Joris van der Hoeven wrote:
>
> > Hi Norbert,
> >
> > Thanks for finding this out; I commited your patch.
> > For sure, many more optimizations of this kind can be done,
> > but it also hampers the readability. It is probably a good idea
> > to make more heavy use of symbols; of course the tree_label class
> > already serves this purpose, but is would probably be good to
> > handle frequently used strings in a similar way,
> > for instance following the lines suggested by Max.
> > However, this probably will require quite a lot of work,
> > if we want to make it clean, systematic and really efficient.
> > If profiling could detect the places which are most critical,
> > a few patches of your kind might actually suffice.
> >
> > There is an even more crucial optimization issue,
> > which concerns a systematic use of const references.
> > A long time ago, David Alouche performed some experiences and
> > noticed a 15% speedup just by treating the basics which
> > are now in Kernel. Maybe a 30% or 50% overall speedup could
> > be achieved by using const references in a systematic way.
> > Again, this has to be done very carefully and systematically,
> > which requires quite a lot of time (and hampers readability;
> > C++ is not really nice in this respect).
> >
> > Best wishes, Joris
> >
> >
> > On Fri, Jun 12, 2009 at 02:51:31PM +0200, Norbert Nemec wrote:
> > > Hi there,
> > >
> > > I just tried to do some profiling of TeXmacs and managed to produce 
> > > a small but significant speedup in the startup time: from 2.0 sec to 
> > > 1.8 sec (averaged over several runs of "time texmacs -q").
> > >
> > > Turns out that quite some time was spent in frequent calls to the 
> > > routine implemented as
> > >
> > > -------
> > > inline bool is_none (url u) { return u->t == tuple ("none"); }
> > > -------
> > >
> > > replacing this by a comparison with a global variable initialized 
> > > just once. Attached is a tiny patch that implements this change.
> > >
> > > Far more important than this change itself, however, is the general 
> > > question that it poses: how many more objects are there in the code 
> > > that are initialized from a constant string over and over again? How 
> > > much efficiency could we gain from a global symbol table that is 
> > > initialized just once?
> > >
> > > Greetings,
> > > Norbert
> > > --
> > > GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
> > > Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01
> >
> >
> > > _______________________________________________
> > > Texmacs-dev mailing list
> > > address@hidden
> > > http://lists.gnu.org/mailman/listinfo/texmacs-dev
> >
> >
> >
> > _______________________________________________
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>
>
>
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Optimize url code by using static variables.

From:  <>


---

 src/src/System/Classes/url.cpp |    2 --
 src/src/System/Classes/url.hpp |   14 ++++++--------
 2 files changed, 6 insertions(+), 10 deletions(-)


diff --git a/src/src/System/Classes/url.cpp b/src/src/System/Classes/url.cpp
index 5d95977..8acbceb 100644
--- a/src/src/System/Classes/url.cpp
+++ b/src/src/System/Classes/url.cpp
@@ -77,8 +77,6 @@
 #define URL_SEPARATOR ':'
 #endif
 
-tree none_tuple= tuple ("none");
-
 /******************************************************************************
 * Unrooted url constructors
 ******************************************************************************/
diff --git a/src/src/System/Classes/url.hpp b/src/src/System/Classes/url.hpp
index 8784e14..cbaf6a0 100644
--- a/src/src/System/Classes/url.hpp
+++ b/src/src/System/Classes/url.hpp
@@ -49,8 +49,6 @@ inline url as_url(tree t) { return url(t); }
 * url constructors
 ******************************************************************************/
 
-extern tree none_tuple;
-
 url url_general (string name, int type);
 url url_unix (string name);
 url url_unix (string dir, string name);
@@ -59,9 +57,9 @@ url url_system (string dir, string name);
 url url_standard (string name);
 url url_standard (string dir, string name);
 
-inline url url_none () { return as_url (none_tuple); }
-inline url url_here () { return as_url (tree (".")); }
-inline url url_parent () { return as_url (tree ("..")); }
+inline url url_none () { static url u = as_url(tuple("none")) ; return u ; }
+inline url url_here () { static url u = as_url(tree(".")); return u ; }
+inline url url_parent () { static url u = as_url(tree("..")); return u ; }
 inline url url_pwd () { return url_system ("$PWD"); }
 
 url url_root (string protocol);       // root url
@@ -80,9 +78,9 @@ inline url url_parent (url u) { return u * url_parent (); }
 * predicates
 ******************************************************************************/
 
-inline bool is_none (url u) { return u->t == none_tuple; }
-inline bool is_here (url u) { return u->t == "."; }
-inline bool is_parent (url u) { return u->t == ".."; }
+inline bool is_none (url u) { static tree t = tuple("none") ; return u->t == 
t; }
+inline bool is_here (url u) { static tree t(".") ; return u->t == t; }
+inline bool is_parent (url u) { static tree t(".."); return u->t == t; }
 inline bool is_atomic (url u) { return is_atomic (u->t); }
 inline bool is_concat (url u) { return is_tuple (u->t, "concat", 2); }
 inline bool is_or (url u) { return is_tuple (u->t, "or", 2); }