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Add comment to explain the implications of not sorting keywords by rhettinger · Pull Request #3331 · python/cpython

rhettinger

In Python 3.6, sorted() was removed from _make_key() for the lru_cache and instead rely on guaranteed keyword argument order preservation.  This makes keyword argument handling faster but it also causes multiple callers with a different keyword argument order to be cached as separate items.  Depending on your point of view, this is either a performance regression (increased number of cache misses) or a performance enhancement (faster computation of keys).

jimmylai pushed a commit to jimmylai/cpython that referenced this pull request

Sep 5, 2017 
* 'master' of https://github.com/python/cpython: (32 commits)
  Conceptually, roots is a set.  Also searching it as a set is a tiny bit faster (python#3338)
  bpo-31343: Include sys/sysmacros.h (python#3318)
  bpo-30102: Call OPENSSL_add_all_algorithms_noconf (python#3112)
  Prevent a few make suspicious warnings. (python#3341)
  Include additional changes to support blurbified NEWS (python#3340)
  Simplify NEWS entry to prevent suspicious warnings. (python#3339)
  bpo-31347: _PyObject_FastCall_Prepend: do not call memcpy if args might not be null (python#3329)
  Revert "bpo-17852: Maintain a list of BufferedWriter objects.  Flush them on exit. (python#1908)" (python#3337)
  bpo-17852: Maintain a list of BufferedWriter objects.  Flush them on exit. (python#1908)
  Fix terminology in comment and add more design rationale. (python#3335)
  Add comment to explain the implications of not sorting keywords (python#3331)
  bpo-31170: Update libexpat from 2.2.3 to 2.2.4 (python#3315)
  bpo-28411: Remove "modules" field from Py_InterpreterState. (python#1638)
  random_triangular:  sqrt() is more accurate than **0.5 (python#3317)
  Travis: use ccache (python#3307)
  remove IRIX support (closes bpo-31341) (python#3310)
  Code clean-up.  Remove unnecessary pre-increment before the loop starts. (python#3312)
  Regen Moduls/clinic/_ssl.c.h (pythonGH-3320)
  bpo-30502: Fix handling of long oids in ssl. (python#2909)
  Cache externals, depending on changes to PCbuild (python#3308)
  ...

GadgetSteve pushed a commit to GadgetSteve/cpython that referenced this pull request

Sep 10, 2017 
…on#3331)

In Python 3.6, sorted() was removed from _make_key() for the lru_cache and instead rely on guaranteed keyword argument order preservation.  This makes keyword argument handling faster but it also causes multiple callers with a different keyword argument order to be cached as separate items.  Depending on your point of view, this is either a performance regression (increased number of cache misses) or a performance enhancement (faster computation of keys).