March 2019 - Boost - lists.preview.boost.org

[interprocess] support for a new synchronisation mechanism
by Dudi Likvornik 06 Mar '19

06 Mar '19

Hi, My name is David, I would like to suggest a new synchronisation mechanism based on linux futex. as far as I saw, its not being supported as of now with in the interprocess communication library. One suggestion is to support a mutex, here is an example, possible partial implementation, based upon the following paper: http://dept-info.labri.fr/~denis/Enseignement/2008-IR/Articles/01-futex.pdf Mutex::Mutex(): m_word(UNLOCK) {} void Mutex::lock() { int lockState = UNLOCK; if(std::atomic_compare_exchange_strong(&m_word, &lockState, static_cast<int>(LOCK_SINGLE)) == false) { if(lockState != LOCK_MANY) lockState = std::atomic_exchange(&m_word, static_cast<int>(LOCK_MANY)); while(lockState != UNLOCK) { #if defined(__linux) syscall(SYS_futex, &m_word, FUTEX_WAIT, LOCK_MANY, nullptr, nullptr, 0); #else throw Exception(__CORE_SOURCE, "wait is not being supported by current platform"); #endif lockState = std::atomic_exchange(&m_word, static_cast<int>(LOCK_MANY)); } } } void Mutex::unlock() { if(std::atomic_fetch_sub(&m_word, 1) == LOCK_SINGLE) return; m_word = UNLOCK; #if defined(__linux) syscall(SYS_futex, &m_word, FUTEX_WAKE, 1, nullptr, nullptr, 0); #else throw Exception(__CORE_SOURCE, "wake is not being supported by current platform"); #endif } bool Mutex::try_lock() { int lockState = UNLOCK; return std::atomic_compare_exchange_strong(&m_word, &lockState, static_cast<int>(LOCK_SINGLE)); } ————————————————————————————————————————————————————————— And a conditional variable: Condition::Condition(): m_command(SLEEP), m_waitersCount(0){} void Condition::signal(Command command) { m_wakeLock.lock(); if(m_waitersCount == 0) { m_wakeLock.unlock(); return; } m_command.store(command, std::memory_order_relaxed); #if defined(__linux) syscall(SYS_futex, &m_command, FUTEX_WAKE, command == NOTIFY_ONE ? 1 : std::numeric_limits<int>::max(), nullptr, nullptr, 0); #else throw Exception(__CORE_SOURCE, "wake is not being supported by current platform"); #endif while(m_command.load(std::memory_order_relaxed) != SLEEP && m_waitersCount.load(std::memory_order_relaxed) != 0){} m_wakeLock.unlock(); } void Condition::wait(std::unique_lock<core::Mutex> &lock) { m_waitersCount++; lock.unlock(); while(true) { while(m_command.load(std::memory_order_relaxed) == SLEEP) #if defined(__linux) syscall(SYS_futex, &m_command, FUTEX_WAIT, SLEEP, nullptr, nullptr, 0); #else throw Exception(__CORE_SOURCE, "wait is not being supported by current platform"); #endif int fromCommand_one = NOTIFY_ONE; if(m_command.compare_exchange_strong(fromCommand_one, static_cast<int>(SLEEP), std::memory_order_relaxed)) { m_waitersCount--; lock.lock(); return; } else if(m_command.load(std::memory_order_relaxed) == NOTIFY_ALL) { if(m_waitersCount.fetch_sub(1, std::memory_order_relaxed) == 1) m_command.store(SLEEP, std::memory_order_relaxed); lock.lock(); return; } } } ConditionVariable::ConditionVariable() {} void ConditionVariable::wait(std::unique_lock<core::Mutex> &lock) { m_condition.wait(lock); } void ConditionVariable::notify_one() { m_condition.signal(Condition::NOTIFY_ONE); } void ConditionVariable::notify_all() { m_condition.signal(Condition::NOTIFY_ALL); } class ConditionVariable { public: ConditionVariable(); ConditionVariable(const ConditionVariable&) = delete; ConditionVariable& operator=(const ConditionVariable&) = delete; void wait(std::unique_lock<Mutex>& lock); template<typename Predict> void wait(std::unique_lock<Mutex>& lock, const Predict& predict) { while(predict() == false) m_condition.wait(lock); } void notify_one(); void notify_all(); private: Condition m_condition; }; Your thoughts of the idea, if any. p.s. Please be soft, its my first post ever :).

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Boost.uBLAS [gsoc19]
by Sarthakag 06 Mar '19

06 Mar '19

Hello, I am Sarthak Agarwal, 3rd-year undergraduate student from Birla Institute of Technology and Science, Pilani - Goa, India currently pursuing a double major MSc. Mathematics and B.E. Computer Science and Engineering. I am an active Competitive Programmer on various online judges for the last 4 years. I am comfortable in C/C++(STL) and Python(Django). I wish to contribute to Boost.uBLAS, specifically to Project 4 on implementing non-negative matrix factorization(NMF). I would also like to know if there are any upcoming ideas to implement in Boost.intrusive. I have completed the Boost Competency test and learned a lot while doing it. How can I share it for valuable feedback? I look forward to your guidance. Sarthak Agarwal -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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Regarding GSOC'19
by Keshav Gupta 05 Mar '19

05 Mar '19

Hi I am Keshav Gupta from India and wanted to work with Boost during GSOC 2019 on the major topic of Boost GIL. So can you tell me how to proceed with? Regards Keshav Gupta

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[variant2] Need rationale for never-empty guarantee
by Andrzej Krzemienski 04 Mar '19

04 Mar '19

Hi Peter, Thank you for writing and sharing this implementation of variant. I am sorry if I am bringing back an issue that has been already discussed and solved before, but I do not understand the rationale behind doing compromises in order to provide the never-empty guarantee. The short rationale provided in Boost.Variant library: https://www.boost.org/doc/libs/1_69_0/doc/html/variant/design.html#variant.… was provided before we got C++11 the moved-from state in the language. Today, it should come as no surprise to programmers that a type might be in a "moved from" state where only a limited interface of an object can be used. The guarantee provided by variant's assignment is not a strong exception safety guarantee: it is possible that my variant has value A, I want to assign value B, and (due to an exception) I end up with value C. If this happens, the only thing I can reasonably do is to either abandon whatever I was doing or reset the variant to the state that I need. So the guarantee that it is not left empty does not seem to be of much use. But the cost to be paid is noticeable. I think that this question should be addressed in the documentation. Regards, Andrzej

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[gsoc19][astronomy] Code for review
by Avinal Kumar 04 Mar '19

04 Mar '19

where should I submit my code for programming competency test ??

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Mentors invitations
by David Bellot 04 Mar '19

04 Mar '19

Dear Boost C++ mentors, it seems we only have 5 mentors this year. It's not a lot. Usually, we have one student per mentor, but we also have 6 to 8 students as well. We need at least one or two mentors more. I've just sent the invite from the GSOC website to become a mentor. If you didn't receive it yet, it's surely because I forgot your name. Can you please send me a reminder now with your correct email address? If you didn't propose to become a mentor but want to now, please let me know as well. Cheers, David

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GSoC 2019 Introduction|Boost.Python-C++-Python Integration Project
by Roopkatha Samanta 04 Mar '19

04 Mar '19

Hi, I am Roopkatha Samanta, studying in 2nd year CSE (undergrad) at Jadavpur University, Kolkata, India. I am very well versed with programming languages like C, C++, Python and Java. I am very much into mathematics too and also interested in machine learning and deep learning. Presenly I am working on two projects in domain of Image Processing as my undergrad project and also trying to develop games on my own. I would like to contribute toBoost.Python-C++-Python Integration Project as my GSoC 2019 Project. Kindly guide me through the process on how to start. Regards, Roopkatha Samanta

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[gsoc19] Logo
by Cem Bassoy 04 Mar '19

04 Mar '19

Hi, is there a chance to change the current logo on the organization list https://summerofcode.withgoogle.com/organizations/?sp-page=5 with https://de.wikipedia.org/wiki/Boost_(C%2B%2B-Bibliothek)#/media/File:Boost.… The current image on the google summer of code page does not look too good and all other organization have smooth ones. Best Cem

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GSoC 2019
by Shourya IIT B 04 Mar '19

04 Mar '19

Respected Sir, I am Parashuram Shourya from India. Currently, I am doing my Master’s in Geoinformatics from Centre of Studies in Resources Engineering(CSRE), Indian Institute of Technology Bombay(IITB). I have a Bachelor's degree in Computer Science and Engineering. Currently, I am learning Machine Learning and High-Performance Computing. I have vast programming experience in C, C++, Python I would love to contribute to The Qt Project in the upcoming Google Summer of Code 2019. I would be very grateful to get any directions to start with so that I can pursue and participate in GSoC 2019 with your organization.

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GSoC 2019: we're in again!
by David Bellot 04 Mar '19

04 Mar '19

Dear Boost community, this year again, Boost C++ has been accepted as a mentor organization for the Google Summer of Code 2019. We are very happy to be part of this program every year because it brings talented students and a substantial amount of money to our organization to support our work toward the best libraries in C++. If you want to be a mentor, please propose your project now here: https://github.com/boostorg/boost/wiki/Google-Summer-of-Code:-2019 It's very important to write your proposal as soon as possible to attract the best students. If you have any questions, please contact me immediately. If you happen to be in Sydney, come and have a chat with me directly. Happy coding, David

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