[be] [task #9084] Reduce bibledit-bin's cpu usage

[Teus Benschop]

URL:
  <http://savannah.nongnu.org/task/?9084>

                 Summary: Reduce bibledit-bin's cpu usage
                 Project: Bibledit
            Submitted by: teus
            Submitted on: Mon 02 Feb 2009 04:57:22 PM CAT
         Should Start On: Mon 02 Feb 2009 12:00:00 AM CAT
   Should be Finished on: Mon 02 Feb 2009 12:00:00 AM CAT
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

I ran bibledit-bin on Linux through callgrind, which is part of  
valgrind.

It seems the bulk of its idle CPU usage is in the following fragment,  
located in editor_aids.cpp:

   for (unsigned int i = 0; i < usfm->styles.size(); i++) {
     if (marker == usfm->styles[i].marker) {
       type = usfm->styles[i].type;
       subtype = usfm->styles[i].subtype;
       break;
     }
   }

This fragment is called every verse_tracker_timeout. Of the 51  
verse_tracker_timeouts captured by my sample, 43,880 calls were made  
to ustring::compare, which is called during evaluation of the if  
statement. Quick math shows about 860 calls to a string comparison per  
verse_tracker_timeout.

I think I might be possible to optimize the loop out completely by  
using a hash table to do the lookup here. This is significant because  
the idle CPU draw from bibledit-bin can be then further reduced,  
allowing for even greater laptop battery life, crucial for some of our  
deployment scenarios.

What do you think? My callgrind output is at https://thedennisons.org/ 
~dand/callgrind.out.19357.gz

dan :)






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