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simpler is better

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This commit is contained in:
Ahmet Inan 2024-03-26 19:15:45 +01:00
commit 270519aa79
2 changed files with 19 additions and 17 deletions
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14
cauchy_prime_field_erasure_coding.hh
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@ -21,7 +21,7 @@ struct CauchyPrimeFieldErasureCoding
return rcp(row + col);
}
// $b_{ij} = \frac{\prod_{k=1}^{n}{(x_j + y_k)(x_k + y_i)}}{(x_j + y_i)\prod_{k \ne j}^{n}{(x_j - x_k)}\prod_{k \ne i}^{n}{(y_i - y_k)}}$
PF inverse_cauchy_matrix(const int *rows, int i, int j, int n)
PF inverse_cauchy_matrix(const IO *rows, int i, int j, int n)
{
#if 0
PF row_j(rows[j]), col_i(i);
@ -83,9 +83,9 @@ struct CauchyPrimeFieldErasureCoding
temp[i] = add(temp[i], b * PF(a[i]));
}
}
void mac_sub(IO *c, const IO *a, PF b, int len, bool first, bool last)
void mac_sub(IO *c, const IO *a, PF b, IO s, int len, bool first, bool last)
{
int s = a[len], v = PF::P-1;
int v = PF::P-1;
if (first && last) {
for (int i = 0; i < len; i++)
c[i] = (b * PF(a[i] == s ? v : a[i]))();
@ -111,7 +111,7 @@ struct CauchyPrimeFieldErasureCoding
++s;
return s;
}
void encode(const IO *data, IO *block, int block_id, int block_len, int block_cnt)
int encode(const IO *data, IO *block, int block_id, int block_len, int block_cnt)
{
assert(block_id >= block_cnt && block_id < int(PF::P) / 2);
assert(block_len < int(PF::P-1) && block_len <= MAX_LEN);
@ -122,13 +122,13 @@ struct CauchyPrimeFieldErasureCoding
int sub = find_unused(block_len);
for (int i = 0; i < block_len; ++i)
block[i] = temp[i]() == PF::P-1 ? sub : temp[i]();
block[block_len] = sub;
return sub;
}
void decode(IO *data, const IO *blocks, const int *block_ids, int block_idx, int block_len, int block_cnt)
void decode(IO *data, const IO *blocks, const IO *block_subs, const IO *block_ids, int block_idx, int block_len, int block_cnt)
{
for (int k = 0; k < block_cnt; k++) {
PF b_ik = inverse_cauchy_matrix(block_ids, block_idx, k, block_cnt);
mac_sub(data, blocks + (block_len+1) * k, b_ik, block_len, !k, k == block_cnt - 1);
mac_sub(data, blocks + block_len * k, b_ik, block_subs[k], block_len, !k, k == block_cnt - 1);
}
}
};