diff options
Diffstat (limited to 'controller/fw/ldpc_decoder.c')
| -rw-r--r-- | controller/fw/ldpc_decoder.c | 94 |
1 files changed, 67 insertions, 27 deletions
diff --git a/controller/fw/ldpc_decoder.c b/controller/fw/ldpc_decoder.c index 10b5a08..fe59d77 100644 --- a/controller/fw/ldpc_decoder.c +++ b/controller/fw/ldpc_decoder.c @@ -5,6 +5,9 @@ #include <math.h> #include <stdio.h> + +void gausselimination(size_t n, size_t k, int8_t *A, int8_t *b); + void inner_logbp( size_t m, size_t n, size_t bits_count, size_t nodes_count, const uint32_t bits_values[], const uint32_t nodes_values[], @@ -60,6 +63,7 @@ int decode(size_t n, size_t nodes_count, size_t bits_count, uint32_t bits[], int for (unsigned int n_iter=0; n_iter<maxiter; n_iter++) { inner_logbp(m, n, bits_count, nodes_count, bits, (uint32_t*)bits_transposed, y, Lq, Lr, n_iter, L_posteriori); + /* float *arrs[3] = {Lq, Lr, L_posteriori}; const char *names[3] = {"Lq", "Lr", "L_posteriori"}; size_t lens[3] = {m*n, m*n, n}; @@ -86,6 +90,7 @@ int decode(size_t n, size_t nodes_count, size_t bits_count, uint32_t bits[], int } printf("\n]\n"); } + */ for (size_t i=0; i<n; i++) out[i] = L_posteriori[i] <= 0.0f; @@ -130,18 +135,18 @@ void inner_logbp( /* step 1 : Horizontal */ unsigned int bits_counter = 0; for (size_t i=0; i<m; i++) { - printf("=== i=%zu\n", i); + //printf("=== i=%zu\n", i); for (size_t p=bits_counter; p<bits_counter+bits_count; p++) { size_t j = bits_values[p]; - printf("\033[38;5;240mj=%04zd ", j); + //printf("\033[38;5;240mj=%04zd ", j); float x = 1; if (n_iter == 0) { for (size_t q=bits_counter; q<bits_counter+bits_count; q++) { if (bits_values[q] != j) { - int lcv = Lc[bits_values[q]]; - char *s = lcv < 0 ? "\033[91m" : (lcv > 0 ? "\033[92m" : "\033[94m"); - printf("nij=%04u Lc=%s%3d\033[38;5;240m ", bits_values[q], s, lcv); + //int lcv = Lc[bits_values[q]]; + //char *s = lcv < 0 ? "\033[91m" : (lcv > 0 ? "\033[92m" : "\033[94m"); + //printf("nij=%04u Lc=%s%3d\033[38;5;240m ", bits_values[q], s, lcv); x *= tanhf(0.5f * Lc[bits_values[q]]); } } @@ -153,7 +158,7 @@ void inner_logbp( } } - printf("\n==== i=%03zd p=%01zd x=%08f\n", i, p-bits_counter, x); + //printf("\n==== i=%03zd p=%01zd x=%08f\n", i, p-bits_counter, x); float num = 1 + x; float denom = 1 - x; @@ -197,31 +202,66 @@ void inner_logbp( } } -/* TODO -def get_message(tG, x): - """Compute the original `n_bits` message from a `n_code` codeword `x`. +/* Compute the original (k) bit message from a (n) bit codeword x. + * + * tG: (n, k)-matrix + * x: (n)-vector + * out: (k)-vector + */ +void get_message(size_t n, size_t k, int8_t *tG, int8_t *x, int8_t *out) { - Parameters - ---------- - tG: array (n_code, n_bits) coding matrix tG. - x: array (n_code,) decoded codeword of length `n_code`. + gausselimination(n, k, tG, x); - Returns - ------- - message: array (n_bits,). Original binary message. + out[k - 1] = x[k - 1]; + for (ssize_t i=k-2; i>=0; i--) { + out[i] = x[i]; - """ - n, k = tG.shape + uint8_t sum = 0; + for (size_t j=i+1; j<k; j++) + sum ^= tG[i*k + j] * out[j]; - rtG, rx = utils.gausselimination(tG, x) + out[i] = !!(out[i] - sum); + } +} - message = np.zeros(k).astype(int) +/* Solve linear system in Z/2Z via Gauss Gauss elimination. + * + * A: (n, k)-matrix + * b: (n)-vector + */ +void gausselimination(size_t n, size_t k, int8_t *A, int8_t *b) { + ssize_t d = k<n ? k : n; + for (ssize_t j=0; j<d; j++) { + + ssize_t pivot = -1; + for (size_t i=j; i<n; i++) { + if (A[i*k + j]) { + pivot = i; + break; + } + } + if (pivot == -1) + continue; + + if (pivot != j) { + for (size_t i=0; i<k; i++) { + int8_t tmp = A[j*k + i]; + A[j*k + i] = A[pivot*k + i]; + A[pivot*k + i] = tmp; + } - message[k - 1] = rx[k - 1] - for i in reversed(range(k - 1)): - message[i] = rx[i] - message[i] -= utils.binaryproduct(rtG[i, list(range(i+1, k))], - message[list(range(i+1, k))]) + int8_t tmp = b[j]; + b[j] = b[pivot]; + b[pivot] = tmp; + } + + for (size_t i=j+1; i<n; i++) { + if (A[i*k + j]) { + for (size_t p=0; p<k; p++) + A[i*k + p] = !!(A[i*k + p] - A[j*k + p]); + b[i] = !!(b[i] - b[j]); + } + } + } +} - return abs(message) -*/ |