[Python-Dev] Python 3 optimizations continued... (original) (raw)

Ned Batchelder ned at nedbatchelder.com
Thu Sep 1 13:29:45 CEST 2011

On 8/30/2011 4:41 PM, stefan brunthaler wrote:

Ok, there there's something else you haven't told us. Are you saying that the original (old) bytecode is still used (and hence written to and read from .pyc files)?

Short answer: yes. Long answer: I added an invocation counter to the code object and keep interpreting in the usual Python interpreter until this counter reaches a configurable threshold. When it reaches this threshold, I create the new instruction format and interpret with this optimized representation. All the macros look exactly the same in the source code, they are just redefined to use the different instruction format. I am at no point serializing this representation or the runtime information gathered by me, as any subsequent invocation might have different characteristics. When the switchover to the new instruction format happens, what happens to sys.settrace() tracing? Will it report the same sequence of line numbers? For a small but important class of program executions, this is more important than speed.

--Ned.

Best, --stefan

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