Re: [boost] GSOC 2015 : Project on Concurrent Hash Tables

Thanks for the frank reply Niall. Firstly, I am interested in working with this project regardless of whether I get selected for GSoC. I am willing to learn C++11 and try to contribute high quality code to Boost. Secondly, I don't mind other candidates leveraging on the code I have written. I believe that's the whole point of open source. Yeah, I understand GSoC is competitive but I am a firm believer that we should keep the best interests of the community over individuals. I have decided to share the piece of code I have written. From what I understand, the code is serving the basic needs of move constructor and move assignment. As I have not extensively used C++11, I am quite unsure of anything else that I have to add to these to make the code more efficient and maintainable. I am just sharing the diff of the source code. I have skipped the diff of unittests here. Please point out any issues or improvements I can work on. Thanks in advance. - concurrent_unordered_map(const concurrent_unordered_map &); - concurrent_unordered_map(concurrent_unordered_map &&) BOOST_NOEXCEPT; + concurrent_unordered_map(const concurrent_unordered_map &); concurrent_unordered_map &operator=(const concurrent_unordered_map &); - concurrent_unordered_map &operator=(concurrent_unordered_map &&) BOOST_NOEXCEPT; public: + concurrent_unordered_map(concurrent_unordered_map &&old_map) BOOST_NOEXCEPT : _hasher(std::move(old_map._hasher)), _key_equal(std::move(old_map._key_eq + { + //Hold the rehash lock + typedef decltype(_rehash_lock) rehash_lock_t; + typedef decltype(old_map._rehash_lock) old_rehash_lock_t; + lock_guard guard(_rehash_lock, adopt_lock_t()); + lock_guard old_guard(old_map._rehash_lock, adopt_lock_t()); + _buckets.exchange(old_map._buckets.load(memory_order_consume), memory_order_release); + old_map._buckets.exchange(nullptr, memory_order_acq_rel); + old_map._buckets = new buckets_type(13); + old_map._oldbucketit = old_map._oldbuckets.begin(); + old_map._oldbuckets.fill(nullptr); + } + + concurrent_unordered_map &operator=(concurrent_unordered_map &&old_map) BOOST_NOEXCEPT + { + if (this != &old_map) { + //Hold the rehash lock + typedef decltype(_rehash_lock) rehash_lock_t; + typedef decltype(old_map._rehash_lock) old_rehash_lock_t; + lock_guard guard(_rehash_lock, adopt_lock_t()); + lock_guard old_guard(old_map._rehash_lock, adopt_lock_t()); + _buckets.exchange(old_map._buckets.load(memory_order_consume), memory_order_release); + _hasher = std::move(old_map._hasher); + _key_equal = std::move(old_map._key_equal); + _max_load_factor = std::move(old_map._max_load_factor); + _min_bucket_capacity = std::move(old_map._min_bucket_capacity); + old_map._buckets.exchange(nullptr, memory_order_acq_rel); + old_map._buckets = new buckets_type(13); + old_map._oldbucketit = old_map._oldbuckets.begin(); + old_map._oldbuckets.fill(nullptr); + } + return *this; + } Thanks, Amarnath On Tue, Feb 24, 2015 at 8:40 PM, Niall Douglas wrote:

On 24 Feb 2015 at 17:30, Amarnath V A wrote:

...

I have coded the move constructor and move assignment operator. I am not sure how good the code is. (Again, let me reiterate I am new to C++11). Will have some time to look at that? Should I share it here in the lists or should I send you a private mail?

It wouldn't be appropriate for me as the likely mentor to comment on anything specifically until GSoC student applications have closed, and then I can treat all submissions equally and fairly. So someone else here will have to comment on your work specifically, as I can only comment in very general and non-specific terms.

Regarding whether to post here with your effort for the community to inspect your work ... well, other candidates you might be competing against will see it as well. They may be able to leverage the discussion here to submit a better application than you. You may find no one here answers, and posting your answer here hasn't benefited you at all.

That said, and assuming anyone bothers to review your work, the fact you were here so early and asked for help in the right kind of way looks very positive, even if your written application compares poorly to another. There is also a valid point that if more of the community who rank GSoC applications have seen your coding skills now AND your coding skills are above average, then the chances are they will rank you more favourably.

Similarly, if your coding skills are below average, the community may well remember that and penalise you for it. If, however, you react really well to critique and show a rapid and marked improvement, then that might favour you.

I do apologise for the equivocal answer. I just wanted you to be aware that there are risks in either route, but there are also benefits. I would say that Boost is an open source software community, and its culture and how it judges others reflects that. Past that, the decision must be yours alone.

Niall --- Boost C++ Libraries Google Summer of Code 2015 admin https://svn.boost.org/trac/boost/wiki/SoC2015

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