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LDPC decoder fully working

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jaseg 2020-02-28 19:30:27 +01:00
parent 89b32316aa
commit 5effadcbaf
3 changed files with 108 additions and 48 deletions
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94
controller/fw/ldpc_decoder.c
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@ -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++) {
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))])
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;
}
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)
*/