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added polar bit freezers, encoders and decoders
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Ahmet Inan
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8 changed files with 985 additions and 0 deletions
146
polar_list_decoder.hh
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146
polar_list_decoder.hh
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/*
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Successive cancellation list decoding of polar codes
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Copyright 2020 Ahmet Inan <inan@aicodix.de>
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*/
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#pragma once
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#include <algorithm>
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#include "polar_helper.hh"
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namespace CODE {
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template <typename TYPE, int M>
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struct PolarListTree
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{
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typedef PolarHelper<TYPE> PH;
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typedef typename PH::PATH PATH;
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typedef typename PH::MAP MAP;
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static const int N = 1 << M;
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static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, const uint8_t *frozen)
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{
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for (int i = 0; i < N/2; ++i)
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soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
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MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen);
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for (int i = 0; i < N/2; ++i)
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soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
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MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen+N/2);
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for (int i = 0; i < N/2; ++i)
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hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
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return vshuf(lmap, rmap);
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}
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};
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template <typename TYPE>
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struct PolarListTree<TYPE, 0>
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{
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typedef PolarHelper<TYPE> PH;
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typedef typename PH::PATH PATH;
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typedef typename PH::MAP MAP;
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static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, const uint8_t *frozen)
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{
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MAP map;
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TYPE hrd, sft = soft[1];
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if (*frozen) {
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for (int k = 0; k < TYPE::SIZE; ++k)
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if (sft.v[k] < 0)
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metric[k] -= sft.v[k];
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hrd = PH::one();
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for (int k = 0; k < TYPE::SIZE; ++k)
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map.v[k] = k;
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} else {
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PATH fork[2*TYPE::SIZE];
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for (int k = 0; k < TYPE::SIZE; ++k)
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fork[k] = fork[k+TYPE::SIZE] = metric[k];
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for (int k = 0; k < TYPE::SIZE; ++k)
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if (sft.v[k] < 0)
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fork[k] -= sft.v[k];
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else
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fork[k+TYPE::SIZE] += sft.v[k];
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int perm[2*TYPE::SIZE];
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for (int k = 0; k < 2*TYPE::SIZE; ++k)
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perm[k] = k;
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std::nth_element(perm, perm+TYPE::SIZE, perm+2*TYPE::SIZE, [fork](int a, int b){ return fork[a] < fork[b]; });
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for (int k = 0; k < TYPE::SIZE; ++k)
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metric[k] = fork[perm[k]];
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for (int k = 0; k < TYPE::SIZE; ++k)
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map.v[k] = perm[k] % TYPE::SIZE;
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for (int k = 0; k < TYPE::SIZE; ++k)
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hrd.v[k] = perm[k] < TYPE::SIZE ? 1 : -1;
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message[*count] = hrd;
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maps[*count] = map;
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++*count;
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}
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*hard = hrd;
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return map;
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}
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};
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template <typename TYPE, int MAX_M>
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class PolarListDecoder
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{
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typedef PolarHelper<TYPE> PH;
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typedef typename TYPE::value_type VALUE;
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typedef typename PH::PATH PATH;
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typedef typename PH::MAP MAP;
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static const int MAX_N = 1 << MAX_M;
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TYPE soft[2*MAX_N];
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TYPE hard[MAX_N];
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MAP maps[MAX_N];
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public:
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void operator()(PATH *metric, TYPE *message, const VALUE *codeword, const uint8_t *frozen, int level)
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{
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assert(level <= MAX_M);
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int count = 0;
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metric[0] = 0;
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for (int k = 1; k < TYPE::SIZE; ++k)
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metric[k] = 1000;
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int length = 1 << level;
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for (int i = 0; i < length; ++i)
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soft[length+i] = vdup<TYPE>(codeword[i]);
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switch (level) {
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case 0: PolarListTree<TYPE, 0>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 1: PolarListTree<TYPE, 1>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 2: PolarListTree<TYPE, 2>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 3: PolarListTree<TYPE, 3>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 4: PolarListTree<TYPE, 4>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 5: PolarListTree<TYPE, 5>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 6: PolarListTree<TYPE, 6>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 7: PolarListTree<TYPE, 7>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 8: PolarListTree<TYPE, 8>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 9: PolarListTree<TYPE, 9>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 10: PolarListTree<TYPE, 10>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 11: PolarListTree<TYPE, 11>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 12: PolarListTree<TYPE, 12>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 13: PolarListTree<TYPE, 13>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 14: PolarListTree<TYPE, 14>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 15: PolarListTree<TYPE, 15>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 16: PolarListTree<TYPE, 16>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 17: PolarListTree<TYPE, 17>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 18: PolarListTree<TYPE, 18>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 19: PolarListTree<TYPE, 19>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 20: PolarListTree<TYPE, 20>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 21: PolarListTree<TYPE, 21>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 22: PolarListTree<TYPE, 22>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 23: PolarListTree<TYPE, 23>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 24: PolarListTree<TYPE, 24>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 25: PolarListTree<TYPE, 25>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 26: PolarListTree<TYPE, 26>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 27: PolarListTree<TYPE, 27>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 28: PolarListTree<TYPE, 28>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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case 29: PolarListTree<TYPE, 29>::decode(metric, message, maps, &count, hard, soft, frozen); break;
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default: assert(false);
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}
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MAP acc = maps[count-1];
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for (int i = count-2; i >= 0; --i) {
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message[i] = vshuf(message[i], acc);
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acc = vshuf(maps[i], acc);
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}
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}
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};
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}
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