[Python-Dev] Thoughts on -O

Delaney, Timothy C (Timothy) tdelaney@avaya.com
Tue, 29 Apr 2003 10:10:39 +1000

Was doing some thinking in the shower this morning, and came up with =
some ideas for specifying optimisation. These are currently quite =
nebulous thoughts ...

We have the current situation:

-O only removes asserts
-OO removes asserts and docstrings.

I think this is an ideal time to revisit the purpose of -O for 2.4 or =

IMO the "vanilla" mode should be a "release" mode. Users should not have =
to use a command-line option to gain "release" optimisations such as =

I would propose that we have the following modes for python to work in.

1. Release/Production mode (no command-line switch)

  - asserts are turned off
  - well-tested/stable optimisations are included
  - possibly additional things, such as not calling trace functions

2. Optimised mode (-O)

  - more experimental optimisations are included i.e. those that may =
have performance improvements in some cases, but penalties in others, =

  - may possibly split this up so individual optimisations can be turned =
on and off as required - this would leave -O by itself as a no-op

3. Docstring elimination mode (-OO)

  - may be specified in addition to optimised mode - it does not imply =
optimised mode

4. Debug mode (-D?)

  - will be the slowest mode - no optimisations - cannot be called with =
either -O or -OO
  - turns on asserts
  - turns on trace functions

I would see Debug mode being used by developers in unit tests, code =
coverage, etc.

.pyc and .pyo files would need to know which optimisations they were =
compiled with so that if they would be loaded again with the "wrong" =
optimisations they would be re-compiled.

Anyway, any thoughts, rebuttals, etc would be of interest. I'd like to =
get some discussion before I create a PEP.


Tim Delaney