/* * nextpnr -- Next Generation Place and Route * * Copyright (C) 2021 Symbiflow Authors * * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * */ #include "sampler.h" #include #include #include NEXTPNR_NAMESPACE_BEGIN static size_t partition_x(std::vector::iterator begin, std::vector::iterator end, const std::vector> &samples) { if (std::distance(begin, end) == 0) { return 0; } // Find the median x value. std::vector xs; xs.reserve(std::distance(begin, end)); for (auto iter = begin; iter != end; ++iter) { xs.push_back(samples[*iter].first); } std::sort(xs.begin(), xs.end()); xs.erase(std::unique(xs.begin(), xs.end()), xs.end()); // Partion on the median x value (e.g. 50% of samples on one side and // 50% of samples on the other side). int32_t x_div = xs[(xs.size() - 1) / 2]; auto split = std::partition(begin, end, [x_div, &samples](size_t index) -> bool { return samples[index].first <= x_div; }); return std::distance(begin, split); } /* Don't both splitting when the partition has less than kMinSplit. */ static constexpr ptrdiff_t kMinSplit = 20; static size_t partition_y(std::vector::iterator begin, std::vector::iterator end, const std::vector> &samples) { if (std::distance(begin, end) == 0) { return 0; } std::vector ys; ys.reserve(std::distance(begin, end)); for (auto iter = begin; iter != end; ++iter) { ys.push_back(samples[*iter].second); } std::sort(ys.begin(), ys.end()); ys.erase(std::unique(ys.begin(), ys.end()), ys.end()); int32_t y_div = ys[(ys.size() - 1) / 2]; auto split = std::partition(begin, end, [y_div, &samples](size_t index) -> bool { return samples[index].second <= y_div; }); return std::distance(begin, split); } static void add_split(std::vector *splits, size_t new_split) { if (splits->back() < new_split) { splits->push_back(new_split); } else if (splits->back() != new_split) { throw std::runtime_error("Split is not consectutive!"); } } void Sampler::divide_samples(size_t target_sample_count, const std::vector> &samples) { // Initialize indicies lookup and make 1 split with entire sample range. indicies.resize(samples.size()); for (size_t i = 0; i < samples.size(); ++i) { indicies[i] = i; } splits.reserve(2); splits.push_back(0); splits.push_back(samples.size()); size_t divisions = std::ceil(std::sqrt(target_sample_count) / 2.); if (divisions == 0) { throw std::runtime_error("Math failure, unreachable!"); } if (divisions > samples.size()) { // Handle cases where there are few samples. return; } // Recursively split samples first 50% / 50% in x direction, and then // 50% / 50% in y direction. Repeat until the bucket is smaller than // kMinSplit or the samples have been divided `divisions` times. std::vector new_splits; for (size_t division_count = 0; division_count < divisions; ++division_count) { new_splits.clear(); new_splits.push_back(0); for (size_t i = 0; i < splits.size() - 1; ++i) { size_t split_begin = splits.at(i); size_t split_end = splits.at(i + 1); if (split_end > indicies.size()) { throw std::runtime_error("split_end is not valid!"); } if (split_begin >= split_end) { throw std::runtime_error("Invalid split from earlier pass!"); } std::vector::iterator begin = indicies.begin() + split_begin; std::vector::iterator end = indicies.begin() + split_end; if (std::distance(begin, end) < kMinSplit) { add_split(&new_splits, split_begin); continue; } // Try to split samples 50/50 in x direction. size_t split = partition_x(begin, end, samples); // Try to split samples 50/50 in y direction after the x split. size_t split_y1 = partition_y(begin, begin + split, samples); size_t split_y2 = partition_y(begin + split, end, samples); // Because the y2 split starts at split, add it here. split_y2 += split; add_split(&new_splits, split_begin); add_split(&new_splits, split_begin + split_y1); add_split(&new_splits, split_begin + split); add_split(&new_splits, split_begin + split_y2); } add_split(&new_splits, samples.size()); if (new_splits.front() != 0) { throw std::runtime_error("Split must start at 0"); } if (new_splits.back() != samples.size()) { throw std::runtime_error("Split must end at last element"); } for (size_t i = 0; i < new_splits.size() - 1; ++i) { if (new_splits[i] >= new_splits[i + 1]) { throw std::runtime_error("Split indicies must be increasing"); } } std::swap(splits, new_splits); } } NEXTPNR_NAMESPACE_END 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186