[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

STINNER Victor added the comment: > Just FYI, there is no PGO run on the official 32-bit builds. I only run it on > the 64-bit build. Aaaah :-) That's good to know ;-) It can explain the performance difference. -- ___ Python tracker

[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

Steve Dower added the comment: Just FYI, there is no PGO run on the official 32-bit builds. I only run it on the 64-bit build. It might be worth investigating differences between the 3.7 and 3.8 implementations of reversed(). -- ___ Python tracke

[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

STINNER Victor added the comment: I close this issue. It's likely just a hiccup in the PGO compilation. It's not the thing that we can easily control. The good thing is that the common code path iter(list) is efficient ;-) > The code for listiter_next() and listreviter_next() is almost the

[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

Terry J. Reedy added the comment: I do not see the within-version slowdown on fresh Windows 10, Pro 64, 32-bit debug builds. 3.7: 26.4, 27.0 3.8: 26.8, 27.1 # installed normal 64 bit is 7.4, 7.4 3.9: 30.2, 30.1 # 10% slower -- components: +Windows nosy: +paul.moore, steve.dower, te

[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

Raymond Hettinger added the comment: The code for listiter_next() and listreviter_next() is almost the same. The main difference that the code for reversed saves the index to Py_ssize_t variable. Maybe that causes a 32-bit to 64-bit conversion and back. The change was made on 30 March 201

[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

Stefan Pochmann added the comment: Oh right. The times are correct, I just summarized wrongly there. -- ___ Python tracker ___ ___

[issue39521] reversed(mylist) much slower on Python 3.8 32-bit for Windows

Change by Stefan Pochmann : -- title: reversed(mylist) much slower on Python 3.8.1 32-bit for Windows -> reversed(mylist) much slower on Python 3.8 32-bit for Windows ___ Python tracker _