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Re: [boost] [Boost-users] [review][fixed_string] FixedString review starts today
by Peter Dimov 02 Dec '19

02 Dec '19

> Wait, I forgot to increment the size! > > http://quick-bench.com/sI71NY7OpQ8ft27HpELko8q_4xM > > Not much improvement anyway. This one at least does something: http://quick-bench.com/g_-BAIENMHQ1Pi1d136FBdp0idQ It still measures nothing though; the string isn't actually written.

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Re: [boost] [Boost-users] [review][fixed_string] FixedString review starts today
by Peter Dimov 02 Dec '19

02 Dec '19

> > Zach Laine wrote: > > Ok, I tried this myself on Quickbench: > > > > http://quick-bench.com/WZPNHFBKI-hFxThBYRZVjndtBho > > I tried to fix that to add the null terminator, but as a result both > push_backs were entirely optimized away. > > http://quick-bench.com/DtPR9Yov1TSzUFeYRx0ipVvUYBk Wait, I forgot to increment the size! http://quick-bench.com/sI71NY7OpQ8ft27HpELko8q_4xM Not much improvement anyway.

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Boost 1.69 on Fedora/PPC64LE: tests results
by REIX, Tony 02 Dec '19

02 Dec '19

Hi, I'm testing Boost v1.69 on Fedora 31 / PPC64LE , as explained at: https://www.boost.org/development/running_regression_tests.html And I see many errors: 1 Failed test out of about 11 Run tests: # cd status # ../b2 ... Passed 101532 tests Failed 10368 tests 90.7% of tests completed sucsessefully Passed 1188 tests Failed 15 tests 98.8% of tests completed sucsessefully I do not know what I made wrong. So, since I do not see any Fedora/PPC64LE machine in the BuildFarm: https://www.boost.org/development/tests/master/developer/summary.html I'd like to know where I could find the summary of the official tests of Boost 1.69 on Fedora/PPC64LE. Thanks/Regards, Tony Reix

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Matrix Multiplication
by Siddhartha Sen 01 Dec '19

01 Dec '19

Having gone through quite a few libraries, the ones that intrigued me the most are Boost.Algorithms and Boost.GIL. I had an idea for Boost.GIl in fact. Basically what I wish to propose(please do correct me if it already exist) is a library that will have the functionality to convert a image to a negative one (I found the conversion of colour image to black and white functionality, but not this). Also, the process can be massively sped up by the incorporation of parallel programming paradigms like OpenMP. Do let me know what you guys think about this.

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[fixed_string] Why "fixed" rather than "static"?
by Andrzej Krzemienski 29 Nov '19

29 Nov '19

Hi Everyone, First, I would like to thank Vinnie and Krystian for writing and sharing the library. While this is not a review, I would like to share a thought about the choice of name. Given that we have static_vector, which seems to be doing a similar thing, why was this library called fixed_string rather than static_string? I note that name fixed_string has some potential to mislead the users as it might imply that it is the size that is fixed (like "a string that always stores 2-letter country codes"). I am not saying that the name choice is wrong. I would just want to see the rationale. Regards, &rzej;

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Re: [boost] [Boost-users] [review][fixed_string] FixedString review starts today
by Peter Dimov 29 Nov '19

29 Nov '19

> and yes, you can write code that will be correct if op+= doesn't check. Maybe you can, but I apparently can't. This is what I just wrote: void my_append( fixed_string<512> & s, std::string_view s1, std::string_view s2 ) { if( s.size() + s1.size() + s2.size() > s.max_size() ) throw std::length_error( "" ); s += s1; s += s2; } Is this correct? (Spoiler: no.)

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Re: [boost] [Boost-users] [review][fixed_string] FixedString review starts today
by Peter Dimov 29 Nov '19

29 Nov '19

> https://godbolt.org/z/Z37Pmx > https://godbolt.org/z/CXHRKQ I forgot to maintain a 0 terminator in this sketch; it's even worse with it. .L5: add rax, 1 movzx ecx, BYTE PTR [rdx] cmp rax, 512 ja .L11 add rdx, 1 mov BYTE PTR [rdi+7+rax], cl mov BYTE PTR [rdi+8+rax], 0 mov QWORD PTR [rdi], rax cmp rsi, rdx jne .L5 https://godbolt.org/z/nhYZQY .L3: movzx ecx, BYTE PTR [rdx+rax] mov BYTE PTR [rdi+8+rax], cl add rax, 1 mov BYTE PTR [rdi+8+rax], 0 mov QWORD PTR [rdi], rax cmp r8, rax jne .L3 https://godbolt.org/z/pGJRWs

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Re: [boost] [review][fixed_string] FixedString review starts Nov 25
by Peter Dimov 28 Nov '19

28 Nov '19

> Also, a synopsis section in the documentation might have been nice, to > allow one to see all the declarations in one place. (Admittedly, the main > header does serve that purpose somewhat.) I join the others in noting the pervasive lack of constexpr and noexcept. Even the default constructor isn't either. Can't think of a reason why it would throw. (The lack of constexpr is much easier to explain.) Also, Traits template parameters were wrong in C++98, and they remain wrong today, even though the committee has propagated that mistake into string_view.

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Re: [boost] [Boost-users] [review][fixed_string] FixedString review starts today
by Peter Dimov 28 Nov '19

28 Nov '19

> I would "precondition" `op+=( char const (&)[ M ] )` (and op=) by failing > at compile time when M > N, because the size is known, but in > fixed_string's case, the size isn't known. No I wouldn't. :-) The size isn't known in this case either. It's better to diagnose_if the whole thing.

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[STLInterfaces] only three operations?
by Andrzej Krzemienski 28 Nov '19

28 Nov '19

Hi, While the formal review of STLInterfaces has not yet started, some early feedback may be of help. The idea to implement relational operators from binary operator- for random_access_iterator looks too clever for me. Maybe this deserves a mention in the documentation it is from operator- that the library will generate all relational ops. For non-contiguous random_access_iterators (like in deque) it might be suboptimal to do it this way: a directly provided operator== might be faster than the one synthesized from operator-. Of course, I can provide the 6 relops operators myself, but I could have only 2 if the facade were capable of generating operator!= from operator== (and similar). Could operator!= for random_access_iterator be generated from operator!= ? Regards, &rzej;

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