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| Original file line number | Diff line number | Diff line change |
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| // Hossein Moein | ||
| // September 13, 2023 | ||
| /* | ||
| Copyright (c) 2023-2028, Hossein Moein | ||
| All rights reserved. | ||
| Redistribution and use in source and binary forms, with or without | ||
| modification, are permitted provided that the following conditions are met: | ||
| * Redistributions of source code must retain the above copyright | ||
| notice, this list of conditions and the following disclaimer. | ||
| * Redistributions in binary form must reproduce the above copyright | ||
| notice, this list of conditions and the following disclaimer in the | ||
| documentation and/or other materials provided with the distribution. | ||
| * Neither the name of Hossein Moein and/or the ThreadPool nor the | ||
| names of its contributors may be used to endorse or promote products | ||
| derived from this software without specific prior written permission. | ||
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND | ||
| ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED | ||
| WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | ||
| DISCLAIMED. IN NO EVENT SHALL Hossein Moein BE LIABLE FOR ANY | ||
| DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES | ||
| (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | ||
| LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND | ||
| ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | ||
| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | ||
| SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| */ | ||
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| #include <ThreadPool/ThreadPool.h> | ||
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| #include <cassert> | ||
| #include <cstdio> | ||
| #include <cstdlib> | ||
| #include <ctime> | ||
| #include <iostream> | ||
| #include <iterator> | ||
| #include <numeric> | ||
| #include <string> | ||
| #include <vector> | ||
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| using namespace hmthrp; | ||
|
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| // ---------------------------------------------------------------------------- | ||
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| static constexpr std::size_t THREAD_COUNT = 5; | ||
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| // ---------------------------------------------------------------------------- | ||
|
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| struct PartialCalc { | ||
|
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| using itr_t = typename std::vector<std::size_t>::iterator; | ||
| using fut_t = std::future<std::size_t>; | ||
|
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| std::size_t | ||
| operator() (const itr_t src_begin, const itr_t src_end, | ||
| itr_t dst_begin, | ||
| fut_t *prev_fut) { | ||
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| std::partial_sum(src_begin, src_end, dst_begin); | ||
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| const std::size_t len = std::distance(src_begin, src_end); | ||
| std::size_t ret_val { *(dst_begin + (len - 1)) }; | ||
|
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| // If we were doing this in place (src == dst), we only needed to | ||
| // add the prev value to the first element of the new block | ||
| // | ||
| if (prev_fut) { | ||
| const std::size_t prev_value { prev_fut->get() }; | ||
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| for (std::size_t i = 0; i < len; ++i) | ||
| *(dst_begin + i) += prev_value; | ||
| ret_val = *(dst_begin + (len - 1)); | ||
| } | ||
| return (ret_val); | ||
| } | ||
| }; | ||
|
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| // ---------------------------------------------------------------------------- | ||
|
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| static void parallel_partial_sum() { | ||
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| std::cout << "Running parallel_partial_sum() ..." << std::endl; | ||
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| constexpr std::size_t n { 1000003 }; | ||
| std::vector<std::size_t> data (n); | ||
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| std::iota(data.begin(), data.end(), 1); | ||
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| std::vector<std::size_t> result (n, 0); | ||
| constexpr std::size_t block_size { n / THREAD_COUNT }; | ||
| std::vector<std::future<std::size_t>> futs; | ||
| ThreadPool thr_pool { THREAD_COUNT }; | ||
|
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| futs.reserve(THREAD_COUNT + 1); | ||
| futs.push_back(thr_pool.dispatch(false, | ||
| PartialCalc{ }, | ||
| data.begin(), | ||
| data.begin() + block_size, | ||
| result.begin(), | ||
| nullptr)); | ||
| for (std::size_t i = block_size; i < n; i += block_size) { | ||
| const std::size_t block_end { | ||
| ((i + block_size) > n) ? n : i + block_size | ||
| }; | ||
| // This depends on reserving the right size | ||
| // | ||
| PartialCalc::fut_t *prev_fut = &(futs.back()); | ||
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| futs.push_back(thr_pool.dispatch(false, | ||
| PartialCalc{ }, | ||
| data.begin() + i, | ||
| data.begin() + block_end, | ||
| result.begin() + i, | ||
| prev_fut)); | ||
| } | ||
| futs.back().get(); // wait for the last thread | ||
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| constexpr std::size_t last_sum { (n * (n + 1)) / 2 }; | ||
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| assert(result.back() == last_sum); | ||
| return; | ||
| } | ||
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| // ---------------------------------------------------------------------------- | ||
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| int main (int, char *[]) { | ||
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| parallel_partial_sum(); | ||
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| return (EXIT_SUCCESS); | ||
| } | ||
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| // ---------------------------------------------------------------------------- | ||
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| // Local Variables: | ||
| // mode:C++ | ||
| // tab-width:4 | ||
| // c-basic-offset:4 | ||
| // End: |