On Wednesday, June 29, 2016 at 12:03:30 PM UTC+5:30, Rustom Mody wrote: > On Wednesday, June 29, 2016 at 11:57:03 AM UTC+5:30, Chris Angelico wrote: > > On Wed, Jun 29, 2016 at 3:55 PM, Rustom Mody wrote: > > >> The transparent shift from machine-word to bignum is what no longer > > >> exists. Both Py2 and Py3 will store large integers as bignums; Py2 has > > >> two separate data types (int and long), with ints generally > > >> outperforming longs, but Py3 simply has one (called int, but > > >> functionally like Py2's long), and does everything with bignums. > > >> There's no longer a boundary - instead, everything gets the "bignum > > >> tax". How steep is that tax? I'm not sure, but microbenchmarking shows > > >> that there definitely is one. How bad is it in real-world code? No > > >> idea. > > >> > > >> ChrisA > > > > > > New to me -- thanks. > > > I thought it did an FSR type covert machine word → BigInt conversion > > > under the hood. > > > Tax is one question > > > Justification for this change is another > > > > CPython doesn't currently do anything like that, but it would be > > perfectly possible to do it invisibly, and thus stay entirely within > > the language spec. I'm not aware of any Python implementation that > > does this, but it wouldn't surprise me if PyPy has some magic like > > that. It's PyPy's kind of thing. > > > > It's also entirely possible that a future CPython will have this kind > > of optimization too. It all depends on someone doing the > > implementation work and then proving that it's worth the complexity. > > > > ChrisA > > Huh? I though I was just describing python2's behavior: > > $ python > Python 2.7.11+ (default, Apr 17 2016, 14:00:29) > [GCC 5.3.1 20160413] on linux2 > Type "help", "copyright", "credits" or "license" for more information. > >>> x=2 > >>> type(x) > <type 'int'> > >>> y=x ** 80 > >>> y > 1208925819614629174706176L > >>> type(y) > <type 'long'>
Um ok I see the ...L there at the end of 2 ** 80 So its not exactly 'under the hood' -- https://mail.python.org/mailman/listinfo/python-list
