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pre-calculate R entries from directly computed first q entries

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This commit is contained in:
Ahmet Inan 2018-12-15 22:09:16 +01:00
commit e06c954148
1 changed files with 28 additions and 17 deletions
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45
ldpc_encoder.hh
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@ -20,29 +20,37 @@ class LDPCEncoder
static const int CNC = TABLE::LINKS_MAX_CN - 2;
uint16_t pos[R * CNC];
uint8_t cnc[R];
uint8_t cnc[q];
public:
LDPCEncoder()
{
for (int i = 0; i < R; ++i)
for (int i = 0; i < q; ++i)
cnc[i] = 0;
int bit_pos = 0;
const int *row_ptr = TABLE::POS;
for (int g = 0; TABLE::LEN[g]; ++g) {
int bit_deg = TABLE::DEG[g];
for (int r = 0; r < TABLE::LEN[g]; ++r) {
int acc_pos[bit_deg];
for (int d = 0; d < bit_deg; ++d)
acc_pos[d] = row_ptr[d];
for (int d = 0; d < bit_deg; ++d) {
int n = row_ptr[d] % q;
int m = row_ptr[d] / q;
pos[CNC*n+cnc[n]++] = bit_pos + (M - m) % M;
}
row_ptr += bit_deg;
for (int j = 0; j < M; ++j) {
for (int d = 0; d < bit_deg; ++d) {
int n = acc_pos[d];
pos[CNC*n+cnc[n]++] = bit_pos;
}
++bit_pos;
for (int d = 0; d < bit_deg; ++d)
acc_pos[d] = (acc_pos[d] + q) % R;
bit_pos += M;
}
}
for (int i = 0; i < q; ++i) {
int cnt = cnc[i];
int offset[cnt], shift[cnt];
for (int c = 0; c < cnt; ++c) {
shift[c] = pos[CNC*i+c] % M;
offset[c] = pos[CNC*i+c] - shift[c];
}
for (int j = 1; j < M; ++j) {
for (int c = 0; c < cnt; ++c) {
shift[c] = (shift[c] + 1) % M;
pos[CNC*(q*j+i)+c] = offset[c] + shift[c];
}
}
}
@ -50,10 +58,13 @@ public:
void operator()(int8_t *data, int8_t *parity)
{
int8_t tmp = 1;
for (int i = 0; i < R; ++i) {
for (int j = 0; j < cnc[i]; ++j)
tmp *= data[pos[CNC*i+j]];
parity[i] = tmp;
for (int j = 0; j < M; ++j) {
for (int i = 0; i < q; ++i) {
int cnt = cnc[i];
for (int c = 0; c < cnt; ++c)
tmp *= data[pos[CNC*(q*j+i)+c]];
parity[q*j+i] = tmp;
}
}
}
};