On Thu, Jun 2, 2016 at 1:06 PM, Jeroen Demeyer <jdeme...@cage.ugent.be> wrote: > On 2016-06-02 21:12, Robert Bradshaw wrote: >>> >>> "if isinstance(x, (int,long))", which is parsed as "if PyInt_Check(x) or >>> PyLong_Check(x)" is slightly slower than "if PyInt_Check(x) || >>> PyLong_Check(x)". >> >> That is very surprising. How much slower? > > With GCC 4.9.3, roughly 4% for a simple loop like > > for x in L: > if isinstance(x, (int, long)): > return True > >> I wonder if >> this is due to gcc's expectations about the likelyhood of truth values >> of the subexpressions in a logical or vs. an if... > > I doubt it. It's just the optimizer which optimizes arithmetic better than > if/goto.
I'm able to replicate the 4% slowdown in that example. However, if I replace L with a list of ints (rather than a list of non-ints) and change the return to an integer increment the isinstance version goes to 4% faster than the || version, so I'd call this microbenchmark a wash. _______________________________________________ cython-devel mailing list cython-devel@python.org https://mail.python.org/mailman/listinfo/cython-devel
