[Python-Dev] insertdict slower?

[Jeremy Hylton]

>>>>> "TP" == Tim Peters <tim.one@home.com> writes:

  TP> [Jeremy]
  >> I was curious about what the DictCreation microbenchmark in
  >> pybench was slower (about 15%) with 2.1 than with 2.0.  I ran
  >> both with profiling enabled (-pg, no -O) and see that insertdict
  >> is a fair bit slower in 2.1.  Anyone with dict implementation
  >> expertise want to hazard a guess about this?

  TP> You don't need to be an expert for this one: just look at the
  TP> code!  There's nothing to it, and not even a comment has changed
  TP> in insertdict since 2.0.  I don't believe the profile.

  [...]

  TP> So you're looking at a buggy profiler, a buggy profiling
  TP> procedure, or a Cache Mystery (the catch-all excuse for anything
  TP> that's incomprehensible without HW-level monitoring tools).
  TP> [...]

I wanted to be sure that some other change to the dictionary code
didn't have the unintended consequence of slowing down insertdict.
There is a real and measurable slowdown in MAL's DictCreation
microbenchmark, which needs to be explained somehow.  insertdict
sounds more plausible than many other explanations.  But I don't have
any more time to think about this before the release.

Jeremy