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[Boost.GIL] GSoC 2020 - FFT implementation
by deb 06 Feb '20

06 Feb '20

Hi, I am a third year undergrad from IIT Bombay. I am interested in PROJECT 1: Image Processing Algorithms for BOOST.GIL . I have gone through the Getting started with Boost, Modular Boost Overview and Contributing page(on git repository for boost.gil) to get a fair idea of how Boost works. I went over the boost Gil library looking for an implementation of FFT(Fast Fourier transform) but could not find one . Since it is listed as a suggested project topic for the GSoC 2020 , I was hoping to implement it as part of my GSoC competency test. I have a few questions though:- a. Should I try and implement 1D-DFT(using FFT) independent from 2D-DFT (which is the more popular among image processing algorithms) ? b. Should I submit the above mentioned algorithms as separate PRs or as a single one? I am choosing FFT over other topics since it is an essential part of many image processing algorithms like Wiener filters, tomographic reconstructions etc. I have worked with image processing algorithms before on college projects and I think that I will be able to pull it off as a GSoC competency test. Thank You. Debabrata Mandal CSE undergrad, IIT Bombay -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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Boost_VERSION widely different between old CMake and new CMake find_package
by Dimitri John Ledkov 05 Feb '20

05 Feb '20

I have the following CMakeLists.txt: project(Boost CXX) cmake_minimum_required(VERSION 3.0) FIND_PACKAGE(Boost COMPONENTS filesystem REQUIRED) message( ${Boost_VERSION} ) In Ubuntu 18.04 LTS (Bionic) this produces: cmake ../ -- The CXX compiler identification is GNU 7.4.0 -- Check for working CXX compiler: /usr/bin/c++ -- Check for working CXX compiler: /usr/bin/c++ -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Detecting CXX compile features -- Detecting CXX compile features - done -- Boost version: 1.65.1 -- Found the following Boost libraries: -- filesystem -- system 106501 -- Configuring done -- Generating done -- Build files have been written to: /root/foo/build As in Boost_VERSION is set to 106501 In Ubuntu 20.04 LTS (Focal, devel release) which uses boost 1.71 with boost cmake files: -- The CXX compiler identification is GNU 9.2.1 -- Check for working CXX compiler: /usr/bin/c++ -- Check for working CXX compiler: /usr/bin/c++ -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Detecting CXX compile features -- Detecting CXX compile features - done -- Found Boost: /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake (found version "1.71.0") found components: filesystem 1.71.0 -- Configuring done -- Generating done -- Build files have been written to: /home/xnox/canonical/boost/debian/tests/srcs/filesystem/foo As in Boost_VERSION is set to 1.71.0 Now, lot of projects have Boost version comparison already and 1.71.0 is less than 106501. This creates problems for example when trying to detect and use new-style pythonXY components, filesystem v3 api, etc. For example I found in Ubuntu packages stanzas like: if (${Boost_VERSION} LESS 104400) Can we please fix Boost_VERSION in the new-style cmake to be compatible / same / similar / higher than the old Boost_VERSION string? -- Regards, Dimitri.

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[Boost.GIL] GSoC 2020 Project 1 - Seeking Mentor
by Ayush Bansal 01 Feb '20

01 Feb '20

Hi, I am a final year undergraduate student from IIT Khraragpur. I was interested in the project “Image Processing Algorithms” to be developed during GSoC 2020. I was mainly interested in implementation of Morphological IP Algorithms, Normalising channels and De-noising filters. I have a good knowledge about most of these algorithms and have worked with a lot of them as a part of my BTech Term Project. In addition to the list of algorithms provided for morphology, I had some other filters which I think could be implemented easily such as - Boundary Extraction, Hole Filling, Thinning and Thickening algorithms. Similarly, for de-noising filters, I was wondering if filters such as Conservative Smoothing, Adaptive Filters etc. could be added to the list. For my competency test, I was interested in doing the implementation of convolution filter and use it to detect edges. However, I did not understand where should I be posting my submission for the same. I have done my previous internship at Google India, where I implemented my code in Google’s Production server in C++, thus I also have the experience of writing good industry level code. I wanted to know if someone would be willing to mentor me for this project. Thanking you in advance. Regards Ayush Bansal Fifth Year Undergraduate Student Department of Computer Science and Engineering IIT Kharagpur

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[Boost.Real] Testing Boost.Real in Visual Studio
by Jai . 30 Jan '20

30 Jan '20

Hi, I would like to contribute to the upcoming Real library. I have cloned the library at BoostGSoC19/Real. I wanted to ask whether it is possible to directly test the library in Visual Studio, or do I have to use CMake to build the project first? Thanks, Jai

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URL library?
by Vinnie Falco 30 Jan '20

30 Jan '20

Is there any interest in a URL library for Boost? This is something that has been requested for a while now, and I've finally gotten around to it. Key features: * Construct a read-only url::view from a string_view * Construct a modifiable url::value from a string_view - Mutate the parts (e.g. set_scheme) - Set encoded or decoded strings: url::value u; u.set_username("Fr ed"); u.set_encoded_password("pass%20word"); - Retrieve encoded or decoded strings: u.username(); // returns decoded std::string u.encoded_password(); // returns encoded string_view For servers, execution paths are provided to avoid all dynamic allocation. For example to retrieve the decoded username: url::static_pool<4000> sp; std::cout << u.username( sp.allocator() ); The std::basic_string returned by username() uses the specified allocator. A server can handle URLs without allocating any memory. There's some punycode conversion routines but I haven't figured out if they should be part of the library, or how they would manifest as APIs (for international domain names). You can perform calculations with URLs using an Allocator (default to std::allocator<char>), or you can use a container with "static storage" (e.g. fixed_string): url::static_value<4000> u; // 4000 char capacity The library is here: <https://github.com/vinniefalco/url> This is still a work in progress, and I'm open to feedback that might help me make better remaining design choices. Thanks

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Re: [boost] Yet Another Container: DynamicArray
by Gavin Lambert 29 Jan '20

29 Jan '20

At 19:02 29/01/2020, Glen Fernandes wrote: >You shouldn't expect that. For any unique_ptr<T, D> you can only >expect that .get() gives you a D::pointer. For default_delete<T> >this might be T*. But it always depends on the Deleter. That seems like a significantly more annoying interface than std::shared_ptr uses. shared_ptr can hold fancy pointers too, but it happens explicitly via using fancy<T> rather than plain T, so the explicit indirection on usage is obvious too. Having that be an implementation detail of the deleter changing the effective "type" of the first template argument (which is what people think of as the type of the pointer, even if the standard disagrees) seems quite annoying. Maybe we should have a type-erased unique ownership pointer as well. I know the reason why we didn't was to avoid heap allocation or wasted storage for the common case, but there ought to be some happy middle ground. >The correct way to get a raw pointer from any >potentially-fancy-pointer x is: to_address(x) > >This can be boost::to_address (C++03 or higher), or >std::to_address (C++20 or higher) Hmm. This is news to me; I don't think I've read about it anywhere in conjunction with unique_ptr. Perhaps since it doesn't actually exist yet (most compilers are still mostly C++17). But eg. <https://en.cppreference.com/w/cpp/memory/unique_ptr>https://en.cppreference.com/w/cpp/memory/unique_ptr appears entirely mute on the topic. (There's a passing reference to fancy pointers but even that doesn't talk about it.)

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Re: [boost] unique_ptr<T, D> and D::pointer and fancy pointers
by Glen Fernandes 29 Jan '20

29 Jan '20

Gavin, in case my explanation in that earlier reply wasn't clear: Given std::unique_ptr<Foo, D> p; 1. Users know that *p and p->x do the right thing by Foo. 2. p.get() will get them a D::pointer. This D::pointer might be Foo*, or it might be offset_ptr<Foo> or it might be alloc_ptr<offset_ptr<Foo>> or any other pointer-like type. To get a Foo* out of p.get() regardless of which of the above three it returns, you can call: Foo* q = std::to_address(p.get()); // C++20 in std, C++03 in boost Or, if you know that p is not a null pointer, you can also use: if (p) { Foo* q = std::addressof(*p); // C++11 in std, C++03 in boost } std::unique_ptr<T, D> was always designed for this (since C++11). Because not all pointers we use are raw pointers. An Allocator::pointer might not be X*, it might be offset_ptr<X>, or it might be aligned_ptr<offset_ptr<X>>. This property of unique_ptr is also unrelated to allocate_unique (which just leverages this with a fancy-pointer around the Allocator::pointer which in turn might be a fancy-pointer). But even today, users are using unique_ptr with non-raw pointers (like Allocators where Allocator::pointer is offset_ptr<X> instead of X*). They don't assume that p.get() returns a raw X* pointer. This might be a lesser known property of unique_ptr to some (especially those that do not work much with custom allocators), but this is the way it has always been and intentionally so. Glen

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Yet Another Container: DynamicArray
by Christian Mazakas 29 Jan '20

29 Jan '20

I've been working on an AllocatorAwareContainer called `dynamic_array` and was wondering if there'd be any interest in including it in Boost. First and foremost, a link to the source code: https://github.com/LeonineKing1199/sleip `dynamic_array` is a heap-allocated array that can't be resized (without entirely re-assigning it). It's useful in cases where you'd normally use `std::vector` but have no need of `push_back`, `emplace_back`, or any of the other size modifiers that the container supports. These kinds of arrays are typically useful in I/O applications which normally only accept a pointer-size pair to write out to. Naturally the question arises, "why use `dynamic_array` in the year 2020 when we have `std::vector` and `boost::allocate_unique`?". `std::vector` imposes a constant storage cost of pointer, size, and capacity. `dynamic_array` only stores a pointer and a size making it slimmer in use-cases where there's no need of a separation between size and capacity. `dynamic_array` also supports constructors `std::vector` doesn't have. For example, `dynamic_array` is constructible from a Range and has a `noinit` constructor. `dynamic_array` even supports array objects which gives it another advantage. `boost::allocate_unique` is a significantly tougher class to beat because it boasts many of the same features: a dynamic allocation done using the supplied Allocator supporting `noinit` construction and array objects with a size (stored in the Deleter of the returned `std::unique_ptr`). And while it is true that `boost::allocate_unique` enables all of this, it still lacks a few key semantics. Namely, `dynamic_array` is copyable. It's also copy assignable and move assignable, including the case where the underlying allocators do not use the same memory resource and will instead perform a piece-wise move of the elements. It's arguable whether or not `std::unique_ptr` should support similar semantics so in the interim, `dynamic_array` is the next best thing. - Chris

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[Boost.Config] Should BOOST_FORCEINLINE depend on NDEBUG?
by dariomt＠gmail.com 29 Jan '20

29 Jan '20

Right now BOOST_FORCEINLINE does not depend on NDEBUG. This means that on Debug builds the code asks to be forced-inlined with optimizations disabled, which does not make much sense to me. This is reflected by a myriad warnings in msvc under level 4 warnings. In fact Multiprecision library works around this issue by defining their own macro BOOST_MP_FORCEINLINE which decays to just inline in Debug builds (boost/multiprecision/detail/number_base.hpp lines 25-29). I think this behavior should be adopted by BOOST_FORCEINLINE. I'm happy to do a PR if there is agreement from maintainers.

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Re: [boost] Yet Another Container: DynamicArray
by Glen Fernandes 29 Jan '20

29 Jan '20

I wrote: > Yes quite. i.e. What you believe is not true about boost::allocate_unique. > > i.e. For auto p = boost::allocate_unique<T[]>(a, n); > assert(p.get().size() == n); > > This is because the unique_ptr stores a pointer adaptor around the > Allocator::pointer which also stores the size. > > So the pointer and size are stored together in the unique_ptr result. Note, that the size is only stored for allocate_unique<T[]>(a,n) but not for allocate_unique<T[N]>(a) since there the N is known at compile time. For auto p = allocate_unique<T[N]>(a); your p.get().size() will return N, but there's no need to store a size_t for N, so we don't. > To get the plain Allocator::pointer out of it you can use p.get().ptr() > > Or, for example, p.release().ptr() for someone who wants to manage > it themselves. Glen

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