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80 lines
2.8 KiB
C++
80 lines
2.8 KiB
C++
/*
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This file is part of TON Blockchain Library.
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TON Blockchain Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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TON Blockchain Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with TON Blockchain Library. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2017-2019 Telegram Systems LLP
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*/
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#include "td/fec/online/Rfc.h"
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namespace td {
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namespace online_code {
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Result<Rfc::Parameters> Rfc::get_parameters(size_t K) {
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return Rfc::Parameters(K, 0.001, 3);
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}
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Rfc::Parameters::Parameters(size_t source_blocks, double epsilon, uint32 quality)
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: source_blocks_(static_cast<uint32>(source_blocks))
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, epsilon_(epsilon)
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, quality_(quality)
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, degree_distribution_{epsilon}
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, outer_encoding_blocks_count_{
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static_cast<uint32>(1 + 0.55 * quality * epsilon * static_cast<double>(source_blocks))} {
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}
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size_t Rfc::Parameters::source_blocks_count() const {
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return source_blocks_;
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}
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size_t Rfc::Parameters::outer_encoding_blocks_count() const {
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return outer_encoding_blocks_count_;
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}
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size_t Rfc::Parameters::estimated_packets() const {
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return size_t(static_cast<double>(source_blocks_count() + outer_encoding_blocks_count()) * (1 + epsilon_));
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}
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Span<uint32> Rfc::Parameters::get_inner_encoding_row(size_t row_id) const {
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Random r(static_cast<uint32>(row_id));
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uint32 degree = degree_distribution_.get_degree(static_cast<uint32>(r() % (1 << 20)) * 1.0 / (1 << 20));
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inner_distribution_.set_random(&r);
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MutableSpan<uint32> res(row_buffer_.data(), degree);
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for (auto &x : res) {
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x = inner_distribution_();
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}
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//std::sort(res.begin(), res.end());
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//res.truncate(std::unique(res.begin(), res.end()) - res.begin());
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return res;
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}
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Rfc::Parameters::DegreeDistribution::DegreeDistribution(double epsilon) {
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uint32 F = static_cast<uint32>(log(epsilon * epsilon / 4) / log(1 - epsilon / 2) + 1 - 1e-9);
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double x = 1 - (1 + 1.0 / F) / (1 + epsilon);
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p_.reserve(F);
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p_.push_back(x);
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for (uint32 i = 2; i <= F; i++) {
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auto y = (1 - x) * F / ((F - 1.0) * i * (i - 1));
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p_.push_back(p_.back() + y);
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}
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}
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uint32 Rfc::Parameters::DegreeDistribution::get_degree(double x) const {
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for (uint32 i = 0; i < p_.size(); i++) {
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if (x < p_[i]) {
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return i + 1;
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}
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}
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UNREACHABLE();
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return 1;
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}
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size_t Rfc::Parameters::DegreeDistribution::get_max_degree() const {
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return p_.size();
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}
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} // namespace online_code
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} // namespace td
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