On Sat, 2013-03-02 at 12:52 -0800, Walter Bright wrote: > On 3/2/2013 12:08 PM, H. S. Teoh wrote: > > On Sat, Mar 02, 2013 at 12:02:08PM -0800, Walter Bright wrote: > >> On 3/2/2013 11:42 AM, Russel Winder wrote: > >>> On Sat, 2013-03-02 at 11:30 -0800, Walter Bright wrote: > >>>> On 3/2/2013 7:43 AM, Russel Winder wrote: > >>>>> For writing interpreters, RPython spanks C. > >>>> > >>>> What's RPython doing that makes it faster? > >>> > >>> Allowing PyPy to have a good JIT compiler. > >> > >> I don't understand. Does that JIT generate faster code than a C > >> compiler would generate? > > > > I don't know, but my wild guess is that a JIT optimizes the *right* > > hotspots based on real-time performance measurements, whereas a lot of C > > programmers are obsessed with optimizing what they *think* are the > > hotspots, but which really aren't. > > I meant what the C *compiler* generates.
Yes because the C/C++/D/etc. compilers are attempting to predict the control flow of the program in execution and optimize all cases for all possibilities. JIT's are just focussing on the runtime bottlenecks with the actual data as being used. This allows for more focussed code generation in the actual context. I would suspect that in many cases the generated code is effectively the same but JITs can often do unexpected and faster codes because they have more data to optimize with and less optimization to do. To say more would require actual comparative data and I suspect no-one on this list will do that. -- Russel. ============================================================================= Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net 41 Buckmaster Road m: +44 7770 465 077 xmpp: rus...@winder.org.uk London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder
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