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aicodix___code/polar_list_decoder.hh
Ahmet Inan 631ec8beef use uint32_t for the frozen bits
2021-07-13 10:50:06 +02:00

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/*
Successive cancellation list decoding of polar codes
Copyright 2020 Ahmet Inan <inan@aicodix.de>
*/
#pragma once
#include <algorithm>
#include "polar_helper.hh"
namespace CODE {
template <typename TYPE, int M>
struct PolarListTree
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, const uint32_t *frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen);
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen+N/2/32);
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 6>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int M = 6;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, const uint32_t *frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen[0]);
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen[1]);
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 5>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int M = 5;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, uint32_t frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen & ((1<<(1<<(M-1)))-1));
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen >> (N/2));
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 4>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int M = 4;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, uint32_t frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen & ((1<<(1<<(M-1)))-1));
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen >> (N/2));
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 3>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int M = 3;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, uint32_t frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen & ((1<<(1<<(M-1)))-1));
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen >> (N/2));
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 2>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int M = 2;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, uint32_t frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen & ((1<<(1<<(M-1)))-1));
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen >> (N/2));
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 1>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int M = 1;
static const int N = 1 << M;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, uint32_t frozen)
{
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::prod(soft[i+N], soft[i+N/2+N]);
MAP lmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard, soft, frozen & ((1<<(1<<(M-1)))-1));
for (int i = 0; i < N/2; ++i)
soft[i+N/2] = PH::madd(hard[i], vshuf(soft[i+N], lmap), vshuf(soft[i+N/2+N], lmap));
MAP rmap = PolarListTree<TYPE, M-1>::decode(metric, message, maps, count, hard+N/2, soft, frozen >> (N/2));
for (int i = 0; i < N/2; ++i)
hard[i] = PH::qmul(vshuf(hard[i], rmap), hard[i+N/2]);
return vshuf(lmap, rmap);
}
};
template <typename TYPE>
struct PolarListTree<TYPE, 0>
{
typedef PolarHelper<TYPE> PH;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static MAP decode(PATH *metric, TYPE *message, MAP *maps, int *count, TYPE *hard, TYPE *soft, uint32_t frozen)
{
MAP map;
TYPE hrd, sft = soft[1];
if (frozen) {
for (int k = 0; k < TYPE::SIZE; ++k)
if (sft.v[k] < 0)
metric[k] -= sft.v[k];
hrd = PH::one();
for (int k = 0; k < TYPE::SIZE; ++k)
map.v[k] = k;
} else {
PATH fork[2*TYPE::SIZE];
for (int k = 0; k < TYPE::SIZE; ++k)
fork[k] = fork[k+TYPE::SIZE] = metric[k];
for (int k = 0; k < TYPE::SIZE; ++k)
if (sft.v[k] < 0)
fork[k] -= sft.v[k];
else
fork[k+TYPE::SIZE] += sft.v[k];
int perm[2*TYPE::SIZE];
for (int k = 0; k < 2*TYPE::SIZE; ++k)
perm[k] = k;
std::nth_element(perm, perm+TYPE::SIZE, perm+2*TYPE::SIZE, [fork](int a, int b){ return fork[a] < fork[b]; });
for (int k = 0; k < TYPE::SIZE; ++k)
metric[k] = fork[perm[k]];
for (int k = 0; k < TYPE::SIZE; ++k)
map.v[k] = perm[k] % TYPE::SIZE;
for (int k = 0; k < TYPE::SIZE; ++k)
hrd.v[k] = perm[k] < TYPE::SIZE ? 1 : -1;
message[*count] = hrd;
maps[*count] = map;
++*count;
}
*hard = hrd;
return map;
}
};
template <typename TYPE, int MAX_M>
class PolarListDecoder
{
static_assert(MAX_M >= 5 && MAX_M <= 29);
typedef PolarHelper<TYPE> PH;
typedef typename TYPE::value_type VALUE;
typedef typename PH::PATH PATH;
typedef typename PH::MAP MAP;
static const int MAX_N = 1 << MAX_M;
TYPE soft[2*MAX_N];
TYPE hard[MAX_N];
MAP maps[MAX_N];
public:
void operator()(PATH *metric, TYPE *message, const VALUE *codeword, const uint32_t *frozen, int level)
{
assert(level <= MAX_M);
int count = 0;
metric[0] = 0;
for (int k = 1; k < TYPE::SIZE; ++k)
metric[k] = 1000;
int length = 1 << level;
for (int i = 0; i < length; ++i)
soft[length+i] = vdup<TYPE>(codeword[i]);
switch (level) {
case 5: PolarListTree<TYPE, 5>::decode(metric, message, maps, &count, hard, soft, *frozen); break;
case 6: PolarListTree<TYPE, 6>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 7: PolarListTree<TYPE, 7>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 8: PolarListTree<TYPE, 8>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 9: PolarListTree<TYPE, 9>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 10: PolarListTree<TYPE, 10>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 11: PolarListTree<TYPE, 11>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 12: PolarListTree<TYPE, 12>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 13: PolarListTree<TYPE, 13>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 14: PolarListTree<TYPE, 14>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 15: PolarListTree<TYPE, 15>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 16: PolarListTree<TYPE, 16>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 17: PolarListTree<TYPE, 17>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 18: PolarListTree<TYPE, 18>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 19: PolarListTree<TYPE, 19>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 20: PolarListTree<TYPE, 20>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 21: PolarListTree<TYPE, 21>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 22: PolarListTree<TYPE, 22>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 23: PolarListTree<TYPE, 23>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 24: PolarListTree<TYPE, 24>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 25: PolarListTree<TYPE, 25>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 26: PolarListTree<TYPE, 26>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 27: PolarListTree<TYPE, 27>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 28: PolarListTree<TYPE, 28>::decode(metric, message, maps, &count, hard, soft, frozen); break;
case 29: PolarListTree<TYPE, 29>::decode(metric, message, maps, &count, hard, soft, frozen); break;
default: assert(false);
}
MAP acc = maps[count-1];
for (int i = count-2; i >= 0; --i) {
message[i] = vshuf(message[i], acc);
acc = vshuf(maps[i], acc);
}
}
};
}
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