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only flip worst T bits

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This commit is contained in:
Ahmet Inan 2020-06-10 20:16:33 +02:00
commit 961e5b19fa
1 changed files with 11 additions and 20 deletions
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31
short_bch_code_decoder.hh
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@ -89,28 +89,19 @@ public:
}
// Chase algorithm
if (K > 6) {
const int num = 4;
int worst[num] = { 0 };
for (int i = 0; i < N; ++i) {
if (std::abs(code[i]) < std::abs(code[worst[0]])) {
worst[3] = worst[2];
worst[2] = worst[1];
worst[1] = worst[0];
worst[0] = i;
} else if (std::abs(code[i]) < std::abs(code[worst[1]])) {
worst[3] = worst[2];
worst[2] = worst[1];
worst[1] = i;
} else if (std::abs(code[i]) < std::abs(code[worst[2]])) {
worst[3] = worst[2];
worst[2] = i;
} else if (std::abs(code[i]) < std::abs(code[worst[3]])) {
worst[3] = i;
}
int worst[T] = { 0 };
for (int k = 0; k < N; ++k) {
int j = 0;
while (j < T && std::abs(code[worst[j]]) < std::abs(code[k]))
++j;
for (int i = T-1; i > j; --i)
worst[i] = worst[i-1];
if (j < T)
worst[j] = k;
}
for (int j = 1; j < (1 << num); ++j) {
for (int j = 1; j < (1 << T); ++j) {
int tmp = 0;
for (int i = 0; i < num; ++i)
for (int i = 0; i < T; ++i)
tmp |= ((j>>i)&1) << worst[i];
int dec = (*this)(cw ^ tmp);
if (dec == word)