[PATCH] lilypond-book performance with new hash subdirs

[John Mandereau]

Hi,

in current lilypond-book, it seems that using sets for reading existing
output file names is a significant speed bottleneck.  I see no good
reason for using sets here, as I'd expect glob.glob and os.listdir to
return lists (or tuples) without duplicate file names.  Using a list iso
a set speeds up lp-book a lot for me; may I commit and push the
following patch?

Cheers,
John

diff --git a/scripts/lilypond-book.py b/scripts/lilypond-book.py
index b29cb97..025861c 100644
--- a/scripts/lilypond-book.py
+++ b/scripts/lilypond-book.py
@@ -1635,14 +1635,14 @@ def write_file_map (lys, name):
 def split_output_files(directory):
     """Returns directory entries in DIRECTORY/XX/ , where XX are hex digits.
 
-    Return value is a set of strings.
+    Return value is a list of strings.
     """
-    files = set ()
+    files = []
     for subdir in glob.glob (os.path.join (directory, '[a-f0-9][a-f0-9]')):
         base_subdir = os.path.split (subdir)[1]
         sub_files = [os.path.join (base_subdir, name)
                      for name in os.listdir (subdir)]
-        files = files.union (sub_files)
+        files += sub_files
     return files
 
 def do_process_cmd (chunks, input_name, options):