On 09/09/2013 08:43 AM, Mark Shannon wrote:
I would like time to investigate this further, but at the moment I think it will either make attribute lookup poorly defined or slow.
Of the top of my head, the problem as a I see it is basically this: Currently, type.__getattribute__() is a fixed point in the lookup of attributes. The proposal means that a fixed point is not reached until the cls parameter of type.__getattribute__() is either object or type, otherwise type.__getattribute__() and type.__locallookup__ must bounce back and forth.
This will slow down *every* attribute lookup for what is a fairly obscure use case.
Looks like there's a patch we can try at http://bugs.python.org/issue18181. Here are Ronald's last timings: ------------------------------------------------------------------------------- PYBENCH 2.1 ------------------------------------------------------------------------------- * using CPython 3.4.0a0 (default, Jul 29 2013, 13:01:34) [GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] * disabled garbage collection * system check interval set to maximum: 2147483647 * using timer: time.perf_counter * timer: resolution=1e-09, implementation=clock_gettime(CLOCK_MONOTONIC) ------------------------------------------------------------------------------- Benchmark: pep447.pybench ------------------------------------------------------------------------------- Rounds: 10 Warp: 10 Timer: time.perf_counter Machine Details: Platform ID: Linux-2.6.32-358.114.1.openstack.el6.x86_64-x86_64-with-centos-6.4-Final Processor: x86_64 Python: Implementation: CPython Executable: /tmp/default-pep447/bin/python3 Version: 3.4.0a0 Compiler: GCC 4.4.7 20120313 (Red Hat 4.4.7-3) Bits: 64bit Build: Jul 29 2013 14:09:12 (#default) Unicode: UCS4 ------------------------------------------------------------------------------- Comparing with: default.pybench ------------------------------------------------------------------------------- Rounds: 10 Warp: 10 Timer: time.perf_counter Machine Details: Platform ID: Linux-2.6.32-358.114.1.openstack.el6.x86_64-x86_64-with-centos-6.4-Final Processor: x86_64 Python: Implementation: CPython Executable: /tmp/default/bin/python3 Version: 3.4.0a0 Compiler: GCC 4.4.7 20120313 (Red Hat 4.4.7-3) Bits: 64bit Build: Jul 29 2013 13:01:34 (#default) Unicode: UCS4 Test minimum run-time average run-time this other diff this other diff ------------------------------------------------------------------------------- BuiltinFunctionCalls: 45ms 44ms +1.3% 45ms 44ms +1.3% BuiltinMethodLookup: 26ms 27ms -2.4% 27ms 27ms -2.2% CompareFloats: 33ms 34ms -0.7% 33ms 34ms -1.1% CompareFloatsIntegers: 66ms 67ms -0.9% 66ms 67ms -0.8% CompareIntegers: 51ms 50ms +0.9% 51ms 50ms +0.8% CompareInternedStrings: 34ms 33ms +0.4% 34ms 34ms -0.4% CompareLongs: 29ms 29ms -0.1% 29ms 29ms -0.0% CompareStrings: 43ms 44ms -1.8% 44ms 44ms -1.8% ComplexPythonFunctionCalls: 44ms 42ms +3.9% 44ms 42ms +4.1% ConcatStrings: 33ms 33ms -0.4% 33ms 33ms -1.0% CreateInstances: 47ms 48ms -2.9% 47ms 49ms -3.4% CreateNewInstances: 35ms 36ms -2.5% 36ms 36ms -2.5% CreateStringsWithConcat: 69ms 70ms -0.7% 69ms 70ms -0.9% DictCreation: 52ms 50ms +3.1% 52ms 50ms +3.0% DictWithFloatKeys: 40ms 44ms -10.1% 43ms 45ms -5.8% DictWithIntegerKeys: 32ms 36ms -11.2% 35ms 37ms -4.6% DictWithStringKeys: 29ms 34ms -15.7% 35ms 40ms -11.0% ForLoops: 30ms 29ms +2.2% 30ms 29ms +2.2% IfThenElse: 38ms 41ms -6.7% 38ms 41ms -6.9% ListSlicing: 36ms 36ms -0.7% 36ms 37ms -1.3% NestedForLoops: 43ms 45ms -3.1% 43ms 45ms -3.2% NestedListComprehensions: 39ms 40ms -1.7% 39ms 40ms -2.1% NormalClassAttribute: 86ms 82ms +5.1% 86ms 82ms +5.0% NormalInstanceAttribute: 42ms 42ms +0.3% 42ms 42ms +0.0% PythonFunctionCalls: 39ms 38ms +3.5% 39ms 38ms +2.8% PythonMethodCalls: 51ms 49ms +3.0% 51ms 50ms +2.8% Recursion: 67ms 68ms -1.4% 67ms 68ms -1.4% SecondImport: 41ms 36ms +12.5% 41ms 36ms +12.6% SecondPackageImport: 45ms 40ms +13.1% 45ms 40ms +13.2% SecondSubmoduleImport: 92ms 95ms -2.4% 95ms 98ms -3.6% SimpleComplexArithmetic: 28ms 28ms -0.1% 28ms 28ms -0.2% SimpleDictManipulation: 57ms 57ms -1.0% 57ms 58ms -1.0% SimpleFloatArithmetic: 29ms 28ms +4.7% 29ms 28ms +4.9% SimpleIntFloatArithmetic: 37ms 41ms -8.5% 37ms 41ms -8.7% SimpleIntegerArithmetic: 37ms 41ms -9.4% 37ms 42ms -10.2% SimpleListComprehensions: 33ms 33ms -1.9% 33ms 34ms -2.9% SimpleListManipulation: 28ms 30ms -4.3% 29ms 30ms -4.1% SimpleLongArithmetic: 26ms 26ms +0.5% 26ms 26ms +0.5% SmallLists: 40ms 40ms +0.1% 40ms 40ms +0.1% SmallTuples: 46ms 47ms -2.4% 46ms 48ms -3.0% SpecialClassAttribute: 126ms 120ms +4.7% 126ms 121ms +4.4% SpecialInstanceAttribute: 42ms 42ms +0.6% 42ms 42ms +0.8% StringMappings: 94ms 91ms +3.9% 94ms 91ms +3.8% StringPredicates: 48ms 49ms -1.7% 48ms 49ms -2.1% StringSlicing: 45ms 45ms +1.4% 46ms 45ms +1.5% TryExcept: 23ms 22ms +4.9% 23ms 22ms +4.8% TryFinally: 32ms 32ms -0.1% 32ms 32ms +0.1% TryRaiseExcept: 17ms 17ms +0.9% 17ms 17ms +0.5% TupleSlicing: 49ms 48ms +1.1% 49ms 49ms +1.0% WithFinally: 48ms 47ms +2.3% 48ms 47ms +2.4% WithRaiseExcept: 45ms 44ms +0.8% 45ms 45ms +0.5% ------------------------------------------------------------------------------- Totals: 2284ms 2287ms -0.1% 2306ms 2308ms -0.1% (this=pep447.pybench, other=default.pybench)