[Python-checkins] peps: Add some comments and acknowledgements

[antoine.pitrou]

http://hg.python.org/peps/rev/d9be356b12a8
changeset:   4865:d9be356b12a8
user:        Antoine Pitrou <solipsis at pitrou.net>
date:        Sat Apr 27 13:24:45 2013 +0200
summary:
  Add some comments and acknowledgements

files:
  pep-3154.txt |  50 ++++++++++++++++++++++++++++++++-------
  1 files changed, 41 insertions(+), 9 deletions(-)


diff --git a/pep-3154.txt b/pep-3154.txt
--- a/pep-3154.txt
+++ b/pep-3154.txt
@@ -7,8 +7,9 @@
 Type: Standards Track
 Content-Type: text/x-rst
 Created: 2011-08-11
-Python-Version: 3.3
+Python-Version: 3.4
 Post-History:
+    http://mail.python.org/pipermail/python-dev/2011-August/112821.html
 Resolution: TBD
 
 
@@ -36,10 +37,10 @@
 object).  The opportunity was not taken at the time to improve the
 protocol in other ways.
 
-This PEP is an attempt to foster a number of small incremental
-improvements in a future new protocol version.  The PEP process is
-used in order to gather as many improvements as possible, because the
-introduction of a new protocol version should be a rare occurrence.
+This PEP is an attempt to foster a number of incremental improvements
+in a new pickle protocol version.  The PEP process is used in order to
+gather as many improvements as possible, because the introduction of a
+new pickle protocol should be a rare occurrence.
 
 
 Proposed changes
@@ -74,11 +75,15 @@
 pickles, and the unpickler refuses them.  Also, there is no "last frame"
 marker.  The last frame is simply the one which ends with a STOP opcode.
 
+A well-written C implementation doesn't need additional memory copies
+for the framing layer, preserving general (un)pickling efficiency.
+
 .. note::
 
-   How the pickler partitions the pickle stream into frames is an
-   implementation detail.  "Closing" a frame as soon as it reaches
-   ~64 KiB should be ok for both performance and pickle size overhead.
+   How the pickler decides to partition the pickle stream into frames is an
+   implementation detail.  For example, "closing" a frame as soon as it
+   reaches ~64 KiB is a reasonable choice for both performance and pickle
+   size overhead.
 
 Binary encoding for all opcodes
 -------------------------------
@@ -138,10 +143,31 @@
 would make many pickles smaller.
 
 
+Alternative ideas
+=================
+
+Prefetching
+-----------
+
+Serhiy Storchaka suggested to replace framing with a special PREFETCH
+opcode (with a 2- or 4-bytes argument) to declare known pickle chunks
+explicitly. Large data may be pickled outside such chunks.  A naïve
+unpickler should be able to skip the PREFETCH opcode and still decode
+pickles properly, but good error handling would require checking that
+the PREFETCH length falls on an opcode boundary.
+
+
 Acknowledgments
 ===============
 
-(...)
+In alphabetic order:
+
+* Alexandre Vassalotti, for starting the second PEP 3154 implementation [6]_
+
+* Serhiy Storchaka, for discussing the framing proposal [6]_
+
+* Stefan Mihaila, for starting the first PEP 3154 implementation as a
+  Google Summer of Code project mentored by Alexandre Vassalotti [7]_.
 
 
 References
@@ -162,6 +188,12 @@
 .. [5] Lib/multiprocessing/forking.py:
    http://hg.python.org/cpython/file/baea9f5f973c/Lib/multiprocessing/forking.py#l54
 
+.. [6] Implement PEP 3154, by Alexandre Vassalotti
+   http://bugs.python.org/issue17810
+
+.. [7] Implement PEP 3154, by Stefan Mihaila
+   http://bugs.python.org/issue15642
+
 
 Copyright
 =========

-- 
Repository URL: http://hg.python.org/peps