If you get three +1’s from the top 6 contributors of C++ code (by volume), I’ll switch to -0, since the ones committing the most C++ code will be the most impacted and probably it should be their decision, imho.
On Sun, Sep 30, 2018 at 12:28 AM kellen sunderland < kellen.sunderl...@gmail.com> wrote: > About 60 but they're all addressed In the ref PR. > > On Sun, Sep 30, 2018, 6:12 AM Chris Olivier <cjolivie...@gmail.com> wrote: > > > How many errors exist in the code base right now if it were to be > enabled? > > > > On Sat, Sep 29, 2018 at 7:03 PM Naveen Swamy <mnnav...@gmail.com> wrote: > > > > > Thanks Kellen & Anton, for your detailed explanation and links to > > > advantages, appreciate it. > > > changing my vote to *-0*, I suggest to show as warnings. > > > > > > On Sat, Sep 29, 2018 at 8:06 PM Anton Chernov <mecher...@gmail.com> > > wrote: > > > > > > > And if you want a more authoritative opinion on that check out what > the > > > C++ > > > > core guidelines are saying [1]: > > > > > > > > > ES.71: Prefer a range-for-statement to a for-statement when there > is > > a > > > > choice > > > > > Reason > > > > > Readability. Error prevention. Efficiency. > > > > > > > > Best regards > > > > Anton > > > > > > > > [1] > > > > > > > > > > > > > > https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Res-for-range > > > > > > > > > > > > сб, 29 сент. 2018 г. в 16:13, Anton Chernov <mecher...@gmail.com>: > > > > > > > > > +1 > > > > > > > > > > Maybe it's not necessary to enforce usage of range-based for, but I > > > would > > > > > highly encourage to to it due to already named advantages. If code > > > would > > > > be > > > > > introduced using the old-style there could be a comment suggesting > > the > > > > new > > > > > way. But why do the manual work and not leave that to the automated > > > tool? > > > > > > > > > > And since it's already automated - wouldn't it be better to keep a > > > > unified > > > > > modern style? > > > > > > > > > > Just to make this a trend - C++ evolves quickly and this will not > be > > > only > > > > > upgrade that would needed to be made. And the easier such upgrades > > get > > > > > accepted the easier in general is to upgrade the codebase. > > > > > > > > > > Soon the standard will get ranges and concepts and this will change > > the > > > > > way C++ applications get written significantly. It is a good habit > to > > > be > > > > > open for changes and keep up with the trends. By using the new > > > > > possibilities the language can offer you prepare yourself for > further > > > > > changes and are more likely to accept them, evolving your > programming > > > > style. > > > > > > > > > > Take a look at a new examples on modern usages (taken from [1]): > > > > > > > > > > // since C++17 > > > > > for (auto&& [first,second] : mymap) { > > > > > // use first and second > > > > > } > > > > > > > > > > // since C++20 > > > > > for (auto& x : foo().items()) { /* .. */ } // undefined behavior if > > > foo() > > > > > returns by value > > > > > for (T thing = foo(); auto& x : thing.items()) { /* ... */ } // OK > > > > > > > > > > // since C++11 > > > > > struct cow_string { /* ... */ }; > > > > > // a copy-on-write string cow_string str = /* ... */; > > > > > // for(auto x : str) { /* ... */ } // may cause deep copy > > > > > for(auto x : std::as_const(str)) { /* ... */ } > > > > > > > > > > Regarding performance: it's really easy to prove that generated > > > assembly > > > > > is not changing at all. There is a really handy tool for that [2]. > > You > > > > can > > > > > check online the assembly for different language constructs and > > > different > > > > > compilers. > > > > > > > > > > Best regards, > > > > > Anton > > > > > > > > > > [1] https://en.cppreference.com/w/cpp/language/range-for > > > > > [2] https://gcc.godbolt.org > > > > > > > > > > сб, 29 сент. 2018 г. в 13:15, kellen sunderland < > > > > > kellen.sunderl...@gmail.com>: > > > > > > > > > >> It's more readable because it's concise and it's consistent for > many > > > > types > > > > >> you're looping over (i.e. primitive arrays, stl iterators, etc all > > > work > > > > >> the > > > > >> same way). It's also useful because it's consistent with other > > > > >> programming > > > > >> languages, making C++ codebases much easier to read for novice and > > > > >> intermediate developers. IMO it also leads to better naming in > loop > > > > >> bodies > > > > >> as the concise style means you're less likely to have important 1 > > > letter > > > > >> variable names describing loop elements (e.g. no int i =0 or it > > ...). > > > > >> More > > > > >> motivation can be found in the cpp standards proposals for C++11 > > > > >> > http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1868.html > > > and > > > > >> http://open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3853.htm. > > > > >> > > > > >> > > > > >> > > > > >> On Sat, Sep 29, 2018 at 6:38 PM Naveen Swamy <mnnav...@gmail.com> > > > > wrote: > > > > >> > > > > >> > Kellen, > > > > >> > > > > > >> > Could you please explain why you think range loops are better > and > > > how > > > > it > > > > >> > improves readability? this is a relatively new feature, many of > > > them > > > > >> are > > > > >> > used to the old syntax, shouldn't we leave it for the developers > > to > > > > >> choose > > > > >> > the one that best suits the need and their familiarity. > > > > >> > In general I support the notion of standardizing where > necessary, > > > > >> enforcing > > > > >> > rules on loops seems little bit like micro-managing how you > should > > > > write > > > > >> > C++ code for MXNet. > > > > >> > > > > > >> > -1(open to change based on new information) > > > > >> > > > > > >> > > > > > >> > > > > > >> > On Fri, Sep 28, 2018 at 5:20 PM Chris Olivier < > > > cjolivie...@gmail.com> > > > > >> > wrote: > > > > >> > > > > > >> > > ok then, my vote is still -1, however, because it’s just > adding > > > > >> needless > > > > >> > > friction for developers imho. > > > > >> > > > > > > >> > > On Fri, Sep 28, 2018 at 7:42 AM kellen sunderland < > > > > >> > > kellen.sunderl...@gmail.com> wrote: > > > > >> > > > > > > >> > > > "Range loops aren’t always the most performant way" Do you > > have > > > an > > > > >> > > example > > > > >> > > > where there's a perf difference? > > > > >> > > > > > > > >> > > > "In addition, sometimes you want the index. Or maybe you > want > > to > > > > >> > iterate > > > > >> > > > backwards, or not start from the first, etc. Maybe you want > > the > > > > >> > iterator > > > > >> > > > because you remove it from the list at the bottom of the > > > loop.... > > > > >> Seems > > > > >> > > > like a rule for the sake of having a rule." > > > > >> > > > > > > > >> > > > I should have been more clear about this point. If you're > > using > > > > the > > > > >> > > index > > > > >> > > > in the loop, doing reverse iteration, or not iterating from > > > > >> > start-to-end > > > > >> > > > this inspection is smart enough to realize it and will not > > > suggest > > > > >> > > > optimizing that type of loop. The loops that would be > changes > > > are > > > > >> > _only_ > > > > >> > > > the loops which are detected as equivalent to range-loops. > > > > Examples > > > > >> > can > > > > >> > > be > > > > >> > > > found here: > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://clang.llvm.org/extra/clang-tidy/checks/modernize-loop-convert.html > > > > >> > > > or you can look at what's been changed in the ref PR. I've > > > > >> initially > > > > >> > set > > > > >> > > > our confidence level at 'reasonable' but we could also set > to > > > > 'safe' > > > > >> > > which > > > > >> > > > would further reduce the number of loops the check would > apply > > > to. > > > > >> > > > > > > > >> > > > -Kellen > > > > >> > > > > > > > >> > > > On Fri, Sep 28, 2018 at 3:54 PM Chris Olivier < > > > > >> cjolivie...@apache.org> > > > > >> > > > wrote: > > > > >> > > > > > > > >> > > > > -1 > > > > >> > > > > > > > > >> > > > > Range loops aren’t always the most performant way. In > > > addition, > > > > >> > > sometimes > > > > >> > > > > you want the index. Or maybe you want to iterate > backwards, > > or > > > > not > > > > >> > > start > > > > >> > > > > from the first, etc. Maybe you want the iterator because > you > > > > >> remove > > > > >> > it > > > > >> > > > from > > > > >> > > > > the list at the bottom of the loop.... Seems like a rule > for > > > the > > > > >> sake > > > > >> > > of > > > > >> > > > > having a rule. > > > > >> > > > > > > > > >> > > > > On Fri, Sep 28, 2018 at 2:12 AM kellen sunderland < > > > > >> > > > > kellen.sunderl...@gmail.com> wrote: > > > > >> > > > > > > > > >> > > > > > Hello MXNet devs, > > > > >> > > > > > > > > > >> > > > > > I'd like to discuss uniformly adopting C++11 range loops > > in > > > > the > > > > >> > MXNet > > > > >> > > > > > project. The benefits I see are: > > > > >> > > > > > > > > > >> > > > > > * Improved C++ readability (examples below). > > > > >> > > > > > * Consistency with other languages. The range-loops > are > > > > quite > > > > >> > > similar > > > > >> > > > > to > > > > >> > > > > > loops almost all other programming languages. Given > > we're a > > > > >> > project > > > > >> > > > that > > > > >> > > > > > supports many languages this language consistency could > be > > > > >> positive > > > > >> > > for > > > > >> > > > > our > > > > >> > > > > > community. > > > > >> > > > > > * Consistency within the same project. Currently > > different > > > > >> authors > > > > >> > > > have > > > > >> > > > > > different loops styles which hurts codebase readability. > > > > >> > > > > > * Best available performance. There are often multiple > > > ways > > > > to > > > > >> > > write > > > > >> > > > > > loops in C++ with subtle differences in performance and > > > memory > > > > >> > usage > > > > >> > > > > > between loop methods. Using range-loops ensures we get > > the > > > > best > > > > >> > > > possible > > > > >> > > > > > perf using an intuitive loop pattern. > > > > >> > > > > > * Slightly lower chance for bugs / OOB accesses when > > > dealing > > > > >> with > > > > >> > > > > indexing > > > > >> > > > > > in an array for example. > > > > >> > > > > > > > > > >> > > > > > If we decide to enable this uniformly throughout the > > project > > > > we > > > > >> can > > > > >> > > > > enable > > > > >> > > > > > this policy with a simple clang-tidy configuration > change. > > > > >> There > > > > >> > > would > > > > >> > > > > be > > > > >> > > > > > no need for reviewers to have to manually provide > feedback > > > > when > > > > >> > > someone > > > > >> > > > > > uses an older C++ loops style. > > > > >> > > > > > > > > > >> > > > > > -Kellen > > > > >> > > > > > > > > > >> > > > > > Reference PR: > > > > >> > https://github.com/apache/incubator-mxnet/pull/12356/ > > > > >> > > > > > Previous clang-tidy discussion on the list: > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://lists.apache.org/thread.html/b0ae5a9df5dfe0d9074cb2ebe432264db4fa2175b89fa43a5f6e36be@%3Cdev.mxnet.apache.org%3E > > > > >> > > > > > > > > > >> > > > > > ------------------------- > > > > >> > > > > > Examples: > > > > >> > > > > > for (auto axis_iter = param.axis.begin() ; axis_iter!= > > > > >> > > > param.axis.end(); > > > > >> > > > > > ++axis_iter) { > > > > >> > > > > > CHECK_LT(*axis_iter, > static_cast<int>(ishape.ndim())); > > > > >> > > > > > stride_[reverse_index] = ishape[*axis_iter]; > > > > >> > > > > > ... > > > > >> > > > > > --> > > > > >> > > > > > for (int axis : param.axis) { > > > > >> > > > > > CHECK_LT(axis, static_cast<int>(ishape.ndim())); > > > > >> > > > > > stride_[reverse_index] = ishape[axis]; > > > > >> > > > > > ... > > > > >> > > > > > -------------------------- > > > > >> > > > > > for (size_t i = 0; i < in_array.size(); i++) { > > > > >> > > > > > auto &nd = in_array[i]; > > > > >> > > > > > pre_temp_buf_.emplace_back(nd.shape(), nd.ctx(), > true, > > > > >> > > nd.dtype()); > > > > >> > > > > > } > > > > >> > > > > > --> > > > > >> > > > > > for (auto & nd : in_array) { > > > > >> > > > > > pre_temp_buf_.emplace_back(nd.shape(), nd.ctx(), > true, > > > > >> > > nd.dtype()); > > > > >> > > > > > } > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > > > > > >
