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705 lines
14 KiB
C++
705 lines
14 KiB
C++
/*
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Generic LDPC algorithms
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Copyright 2018 Ahmet Inan <xdsopl@gmail.com>
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*/
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#ifndef GENERIC_HH
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#define GENERIC_HH
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#include "exclusive_reduce.h"
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namespace ldpctool {
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template <typename TYPE>
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struct NormalUpdate
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{
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static void update(TYPE *a, TYPE b)
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{
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*a = b;
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}
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};
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template <typename TYPE>
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struct SelfCorrectedUpdate
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{
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static void update(TYPE *a, TYPE b)
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{
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*a = (*a == TYPE(0) || (*a < TYPE(0)) == (b < TYPE(0))) ? b : TYPE(0);
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}
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};
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template <typename TYPE, typename UPDATE>
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struct MinSumAlgorithm
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{
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static TYPE zero()
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{
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return 0;
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}
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static TYPE one()
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{
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return 1;
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}
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static TYPE min(TYPE a, TYPE b)
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{
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return std::min(a, b);
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}
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static TYPE sign(TYPE a, TYPE b)
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{
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return b < TYPE(0) ? -a : b > TYPE(0) ? a : TYPE(0);
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}
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static void finalp(TYPE *links, int cnt)
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{
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TYPE mags[cnt], mins[cnt];
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for (int i = 0; i < cnt; ++i)
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mags[i] = std::abs(links[i]);
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CODE::exclusive_reduce(mags, mins, cnt, min);
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TYPE signs[cnt];
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CODE::exclusive_reduce(links, signs, cnt, sign);
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for (int i = 0; i < cnt; ++i)
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links[i] = sign(mins[i], signs[i]);
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}
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static TYPE add(TYPE a, TYPE b)
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{
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return a + b;
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}
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static TYPE sub(TYPE a, TYPE b)
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{
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return a - b;
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}
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static bool bad(TYPE v, int)
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{
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return v <= TYPE(0);
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}
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static void update(TYPE *a, TYPE b)
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{
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UPDATE::update(a, b);
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}
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};
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template <typename UPDATE>
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struct MinSumAlgorithm<float, UPDATE>
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{
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static float zero()
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{
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return 0.f;
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}
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static float one()
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{
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return 1.f;
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}
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static float min(float a, float b)
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{
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return std::min(a, b);
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}
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static int xor_(int a, int b)
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{
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return a ^ b;
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}
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static void finalp(float *links, int cnt)
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{
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int mask = 0x80000000;
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float mags[cnt], mins[cnt];
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for (int i = 0; i < cnt; ++i)
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mags[i] = std::abs(links[i]);
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CODE::exclusive_reduce(mags, mins, cnt, min);
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int signs[cnt];
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CODE::exclusive_reduce(reinterpret_cast<int *>(links), signs, cnt, xor_);
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for (int i = 0; i < cnt; ++i)
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signs[i] &= mask;
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for (int i = 0; i < cnt; ++i)
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reinterpret_cast<int *>(links)[i] = signs[i] | reinterpret_cast<int *>(mins)[i];
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}
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static float sign(float a, float b)
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{
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return b < 0.f ? -a : b > 0.f ? a : 0.f;
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}
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static float add(float a, float b)
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{
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return a + b;
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}
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static float sub(float a, float b)
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{
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return a - b;
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}
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static bool bad(float v, int)
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{
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return v <= 0.f;
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}
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static void update(float *a, float b)
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{
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UPDATE::update(a, b);
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}
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};
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template <typename UPDATE>
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struct MinSumAlgorithm<int8_t, UPDATE>
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{
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static int8_t zero()
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{
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return 0;
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}
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static int8_t one()
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{
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return 1;
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}
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static int8_t add(int8_t a, int8_t b)
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{
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int16_t x = int16_t(a) + int16_t(b);
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x = std::min<int16_t>(std::max<int16_t>(x, -128), 127);
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return x;
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}
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static int8_t sub(int8_t a, int8_t b)
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{
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int16_t x = int16_t(a) - int16_t(b);
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x = std::min<int16_t>(std::max<int16_t>(x, -128), 127);
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return x;
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}
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static int8_t min(int8_t a, int8_t b)
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{
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return std::min(a, b);
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}
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static int8_t xor_(int8_t a, int8_t b)
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{
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return a ^ b;
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}
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static int8_t sqabs(int8_t a)
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{
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return std::abs(std::max<int8_t>(a, -127));
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}
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static int8_t sign(int8_t a, int8_t b)
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{
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return b < 0 ? -a : b > 0 ? a : 0;
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}
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static void finalp(int8_t *links, int cnt)
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{
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int8_t mags[cnt], mins[cnt];
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for (int i = 0; i < cnt; ++i)
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mags[i] = sqabs(links[i]);
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CODE::exclusive_reduce(mags, mins, cnt, min);
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int8_t signs[cnt];
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CODE::exclusive_reduce(links, signs, cnt, xor_);
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for (int i = 0; i < cnt; ++i)
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signs[i] |= 127;
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for (int i = 0; i < cnt; ++i)
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links[i] = sign(mins[i], signs[i]);
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}
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static bool bad(int8_t v, int)
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{
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return v <= 0;
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}
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static void update(int8_t *a, int8_t b)
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{
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UPDATE::update(a, std::min<int8_t>(std::max<int8_t>(b, -32), 31));
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}
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};
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template <typename TYPE, typename UPDATE, int FACTOR>
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struct OffsetMinSumAlgorithm
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{
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static TYPE zero()
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{
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return 0;
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}
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static TYPE one()
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{
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return 1;
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}
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static TYPE min(TYPE a, TYPE b)
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{
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return std::min(a, b);
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}
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static TYPE sign(TYPE a, TYPE b)
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{
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return b < TYPE(0) ? -a : b > TYPE(0) ? a : TYPE(0);
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}
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static void finalp(TYPE *links, int cnt)
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{
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TYPE beta = 0.5 * FACTOR;
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TYPE mags[cnt], mins[cnt];
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for (int i = 0; i < cnt; ++i)
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mags[i] = std::max(std::abs(links[i]) - beta, TYPE(0));
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CODE::exclusive_reduce(mags, mins, cnt, min);
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TYPE signs[cnt];
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CODE::exclusive_reduce(links, signs, cnt, sign);
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for (int i = 0; i < cnt; ++i)
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links[i] = sign(mins[i], signs[i]);
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}
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static TYPE add(TYPE a, TYPE b)
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{
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return a + b;
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}
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static TYPE sub(TYPE a, TYPE b)
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{
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return a - b;
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}
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static bool bad(TYPE v, int)
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{
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return v <= TYPE(0);
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}
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static void update(TYPE *a, TYPE b)
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{
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UPDATE::update(a, b);
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}
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};
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template <typename UPDATE, int FACTOR>
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struct OffsetMinSumAlgorithm<int8_t, UPDATE, FACTOR>
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{
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static int8_t zero()
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{
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return 0;
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}
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static int8_t one()
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{
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return 1;
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}
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static int8_t add(int8_t a, int8_t b)
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{
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int16_t x = int16_t(a) + int16_t(b);
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x = std::min<int16_t>(std::max<int16_t>(x, -128), 127);
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return x;
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}
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static int8_t sub(int8_t a, int8_t b)
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{
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int16_t x = int16_t(a) - int16_t(b);
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x = std::min<int16_t>(std::max<int16_t>(x, -128), 127);
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return x;
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}
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static uint8_t subu(uint8_t a, uint8_t b)
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{
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int16_t x = int16_t(a) - int16_t(b);
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x = std::max<int16_t>(x, 0);
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return x;
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}
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static int8_t min(int8_t a, int8_t b)
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{
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return std::min(a, b);
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}
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static int8_t xor_(int8_t a, int8_t b)
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{
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return a ^ b;
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}
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static int8_t sqabs(int8_t a)
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{
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return std::abs(std::max<int8_t>(a, -127));
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}
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static int8_t sign(int8_t a, int8_t b)
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{
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return b < 0 ? -a : b > 0 ? a : 0;
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}
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static void finalp(int8_t *links, int cnt)
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{
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int8_t beta = std::nearbyint(0.5 * FACTOR);
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int8_t mags[cnt], mins[cnt];
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for (int i = 0; i < cnt; ++i)
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mags[i] = subu(sqabs(links[i]), beta);
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CODE::exclusive_reduce(mags, mins, cnt, min);
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int8_t signs[cnt];
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CODE::exclusive_reduce(links, signs, cnt, xor_);
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for (int i = 0; i < cnt; ++i)
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signs[i] |= 127;
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for (int i = 0; i < cnt; ++i)
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links[i] = sign(mins[i], signs[i]);
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}
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static bool bad(int8_t v, int)
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{
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return v <= 0;
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}
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static void update(int8_t *a, int8_t b)
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{
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UPDATE::update(a, std::min<int8_t>(std::max<int8_t>(b, -32), 31));
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}
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};
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template <typename TYPE, typename UPDATE, int FACTOR>
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struct MinSumCAlgorithm
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{
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static TYPE zero()
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{
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return 0;
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}
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static TYPE one()
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{
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return 1;
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}
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static TYPE correction_factor(TYPE a, TYPE b)
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{
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if (1) {
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TYPE c = TYPE(FACTOR) / TYPE(2);
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TYPE apb = std::abs(a + b);
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TYPE amb = std::abs(a - b);
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if (apb < TYPE(2) && amb > TYPE(2) * apb)
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return c;
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if (amb < TYPE(2) && apb > TYPE(2) * amb)
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return -c;
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return 0;
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}
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return std::log(TYPE(1)+std::exp(-std::abs(a+b))) - std::log(TYPE(1)+std::exp(-std::abs(a-b)));
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}
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static TYPE sign(TYPE a, TYPE b)
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{
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return b < TYPE(0) ? -a : b > TYPE(0) ? a : TYPE(0);
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}
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static TYPE min(TYPE a, TYPE b)
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{
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TYPE m = std::min(std::abs(a), std::abs(b));
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TYPE x = sign(sign(m, a), b);
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x += correction_factor(a, b);
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return x;
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}
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static void finalp(TYPE *links, int cnt)
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{
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TYPE tmp[cnt];
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CODE::exclusive_reduce(links, tmp, cnt, min);
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for (int i = 0; i < cnt; ++i)
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links[i] = tmp[i];
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}
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static TYPE add(TYPE a, TYPE b)
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{
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return a + b;
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}
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static TYPE sub(TYPE a, TYPE b)
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{
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return a - b;
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}
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static bool bad(TYPE v, int)
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{
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return v <= TYPE(0);
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}
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static void update(TYPE *a, TYPE b)
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{
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UPDATE::update(a, b);
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}
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};
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template <typename UPDATE, int FACTOR>
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struct MinSumCAlgorithm<float, UPDATE, FACTOR>
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{
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static float zero()
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{
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return 0.f;
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}
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static float one()
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{
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return 1.f;
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}
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static float correction_factor(float a, float b)
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{
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float c = 0.5f;
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float apb = std::abs(a + b);
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float amb = std::abs(a - b);
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if (apb < 2.f && amb > 2.f * apb)
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return c;
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if (amb < 2.f && apb > 2.f * amb)
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return -c;
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return 0;
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}
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static float min(float a, float b)
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{
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int mask = 0x80000000;
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float m = std::min(std::abs(a), std::abs(b));
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int tmp = (mask & (*reinterpret_cast<int *>(&a) ^ *reinterpret_cast<int *>(&b))) | *reinterpret_cast<int *>(&m);
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float x = *reinterpret_cast<float *>(&tmp);
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x += correction_factor(a, b);
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return x;
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}
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static void finalp(float *links, int cnt)
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{
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float tmp[cnt];
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CODE::exclusive_reduce(links, tmp, cnt, min);
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for (int i = 0; i < cnt; ++i)
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links[i] = tmp[i];
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}
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static float sign(float a, float b)
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{
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return b < 0.f ? -a : b > 0.f ? a : 0.f;
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}
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static float add(float a, float b)
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{
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return a + b;
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}
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static float sub(float a, float b)
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{
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return a - b;
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}
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static bool bad(float v, int)
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{
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return v <= 0.f;
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}
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static void update(float *a, float b)
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{
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UPDATE::update(a, b);
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}
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};
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template <typename UPDATE, int FACTOR>
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struct MinSumCAlgorithm<int8_t, UPDATE, FACTOR>
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{
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static int8_t zero()
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{
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return 0;
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}
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static int8_t one()
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{
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return 1;
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}
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static int8_t add(int8_t a, int8_t b)
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{
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int16_t x = int16_t(a) + int16_t(b);
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x = std::min<int16_t>(std::max<int16_t>(x, -128), 127);
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return x;
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}
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static uint8_t addu(uint8_t a, uint8_t b)
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{
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int16_t x = int16_t(a) + int16_t(b);
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x = std::min<int16_t>(x, 255);
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return x;
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}
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static int8_t sub(int8_t a, int8_t b)
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{
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int16_t x = int16_t(a) - int16_t(b);
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x = std::min<int16_t>(std::max<int16_t>(x, -128), 127);
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return x;
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}
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static uint8_t subu(uint8_t a, uint8_t b)
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{
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int16_t x = int16_t(a) - int16_t(b);
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x = std::max<int16_t>(x, 0);
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return x;
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}
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static uint8_t abs(int8_t a)
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{
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return std::abs<int16_t>(a);
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}
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static int8_t sqabs(int8_t a)
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{
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return std::abs(std::max<int8_t>(a, -127));
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}
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static int8_t sign(int8_t a, int8_t b)
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{
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return b < 0 ? -a : b > 0 ? a : 0;
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}
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static int8_t correction_factor(int8_t a, int8_t b)
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{
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uint8_t factor2 = FACTOR * 2;
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uint8_t c = FACTOR / 2;
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uint8_t apb = abs(add(a, b));
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uint8_t apb2 = addu(apb, apb);
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uint8_t amb = abs(sub(a, b));
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uint8_t amb2 = addu(amb, amb);
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if (subu(factor2, apb) && subu(amb, apb2))
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return c;
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if (subu(factor2, amb) && subu(apb, amb2))
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return -c;
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return 0;
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}
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static int8_t min(int8_t a, int8_t b)
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{
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int8_t m = std::min(sqabs(a), sqabs(b));
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int8_t x = sign(sign(m, a), b);
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x = add(x, correction_factor(a, b));
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return x;
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}
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static void finalp(int8_t *links, int cnt)
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{
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int8_t tmp[cnt];
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CODE::exclusive_reduce(links, tmp, cnt, min);
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for (int i = 0; i < cnt; ++i)
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links[i] = tmp[i];
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}
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static bool bad(int8_t v, int)
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{
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return v <= 0;
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}
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static void update(int8_t *a, int8_t b)
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{
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UPDATE::update(a, std::min<int8_t>(std::max<int8_t>(b, -32), 31));
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}
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};
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template <typename TYPE, typename UPDATE>
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struct LogDomainSPA
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{
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static TYPE zero()
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{
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return 0;
|
|
}
|
|
static TYPE one()
|
|
{
|
|
return 1;
|
|
}
|
|
static TYPE phi(TYPE x)
|
|
{
|
|
x = std::min(std::max(x, TYPE(0.000001)), TYPE(14.5));
|
|
return std::log(std::exp(x)+TYPE(1)) - std::log(std::exp(x)-TYPE(1));
|
|
}
|
|
static TYPE add(TYPE a, TYPE b)
|
|
{
|
|
return a + b;
|
|
}
|
|
static TYPE sub(TYPE a, TYPE b)
|
|
{
|
|
return a - b;
|
|
}
|
|
static TYPE sign(TYPE a, TYPE b)
|
|
{
|
|
return b < TYPE(0) ? -a : b > TYPE(0) ? a : TYPE(0);
|
|
}
|
|
static void finalp(TYPE *links, int cnt)
|
|
{
|
|
TYPE mags[cnt], sums[cnt];
|
|
for (int i = 0; i < cnt; ++i)
|
|
mags[i] = phi(std::abs(links[i]));
|
|
CODE::exclusive_reduce(mags, sums, cnt, add);
|
|
|
|
TYPE signs[cnt];
|
|
CODE::exclusive_reduce(links, signs, cnt, sign);
|
|
|
|
for (int i = 0; i < cnt; ++i)
|
|
links[i] = sign(phi(sums[i]), signs[i]);
|
|
}
|
|
static bool bad(TYPE v, int)
|
|
{
|
|
return v <= TYPE(0);
|
|
}
|
|
static void update(TYPE *a, TYPE b)
|
|
{
|
|
UPDATE::update(a, b);
|
|
}
|
|
};
|
|
|
|
template <typename TYPE, typename UPDATE, int LAMBDA>
|
|
struct LambdaMinAlgorithm
|
|
{
|
|
static TYPE zero()
|
|
{
|
|
return 0;
|
|
}
|
|
static TYPE one()
|
|
{
|
|
return 1;
|
|
}
|
|
static TYPE phi(TYPE x)
|
|
{
|
|
x = std::min(std::max(x, TYPE(0.000001)), TYPE(14.5));
|
|
return std::log(std::exp(x)+TYPE(1)) - std::log(std::exp(x)-TYPE(1));
|
|
}
|
|
static TYPE add(TYPE a, TYPE b)
|
|
{
|
|
return a + b;
|
|
}
|
|
static TYPE sub(TYPE a, TYPE b)
|
|
{
|
|
return a - b;
|
|
}
|
|
static TYPE sign(TYPE a, TYPE b)
|
|
{
|
|
return b < TYPE(0) ? -a : b > TYPE(0) ? a : TYPE(0);
|
|
}
|
|
static void finalp(TYPE *links, int cnt)
|
|
{
|
|
typedef std::pair<TYPE, int> Pair;
|
|
Pair mags[cnt];
|
|
for (int i = 0; i < cnt; ++i)
|
|
mags[i] = Pair(std::abs(links[i]), i);
|
|
std::nth_element(mags, mags+LAMBDA, mags+cnt, [](Pair a, Pair b){ return a.first < b.first; });
|
|
|
|
TYPE sums[cnt];
|
|
for (int i = 0; i < cnt; ++i) {
|
|
int j = 0;
|
|
if (i == mags[0].second)
|
|
++j;
|
|
sums[i] = phi(mags[j].first);
|
|
for (int l = 1; l < LAMBDA; ++l) {
|
|
++j;
|
|
if (i == mags[j].second)
|
|
++j;
|
|
sums[i] += phi(mags[j].first);
|
|
}
|
|
}
|
|
|
|
TYPE signs[cnt];
|
|
CODE::exclusive_reduce(links, signs, cnt, sign);
|
|
|
|
for (int i = 0; i < cnt; ++i)
|
|
links[i] = sign(phi(sums[i]), signs[i]);
|
|
}
|
|
static bool bad(TYPE v, int)
|
|
{
|
|
return v <= TYPE(0);
|
|
}
|
|
static void update(TYPE *a, TYPE b)
|
|
{
|
|
UPDATE::update(a, b);
|
|
}
|
|
};
|
|
|
|
template <typename TYPE, typename UPDATE>
|
|
struct SumProductAlgorithm
|
|
{
|
|
static TYPE zero()
|
|
{
|
|
return 0;
|
|
}
|
|
static TYPE one()
|
|
{
|
|
return 1;
|
|
}
|
|
static TYPE prep(TYPE x)
|
|
{
|
|
return std::tanh(TYPE(0.5) * x);
|
|
}
|
|
static TYPE postp(TYPE x)
|
|
{
|
|
return TYPE(2) * std::atanh(x);
|
|
}
|
|
static TYPE mul(TYPE a, TYPE b)
|
|
{
|
|
return a * b;
|
|
}
|
|
static TYPE sign(TYPE a, TYPE b)
|
|
{
|
|
return b < TYPE(0) ? -a : b > TYPE(0) ? a : TYPE(0);
|
|
}
|
|
static void finalp(TYPE *links, int cnt)
|
|
{
|
|
TYPE in[cnt], out[cnt];
|
|
for (int i = 0; i < cnt; ++i)
|
|
in[i] = prep(links[i]);
|
|
CODE::exclusive_reduce(in, out, cnt, mul);
|
|
for (int i = 0; i < cnt; ++i)
|
|
links[i] = postp(out[i]);
|
|
}
|
|
static TYPE add(TYPE a, TYPE b)
|
|
{
|
|
return a + b;
|
|
}
|
|
static TYPE sub(TYPE a, TYPE b)
|
|
{
|
|
return a - b;
|
|
}
|
|
static bool bad(TYPE v, int)
|
|
{
|
|
return v <= TYPE(0);
|
|
}
|
|
static void update(TYPE *a, TYPE b)
|
|
{
|
|
UPDATE::update(a, b);
|
|
}
|
|
};
|
|
|
|
} // namespace ldpctool
|
|
|
|
#endif
|