From 5effadcbaf66f476c8fffefa2c349676f41c3f52 Mon Sep 17 00:00:00 2001
From: jaseg <git-bigdata-wsl-arch@jaseg.de>
Date: Fri, 28 Feb 2020 19:30:27 +0100
Subject: LDPC decoder fully working

---
 controller/fw/ldpc_decoder.c       | 94 +++++++++++++++++++++++++++-----------
 controller/fw/ldpc_decoder_test.py | 35 ++++++++++----
 controller/fw/test_decoder.py      | 27 +++++------
 3 files changed, 108 insertions(+), 48 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)
-*/
diff --git a/controller/fw/ldpc_decoder_test.py b/controller/fw/ldpc_decoder_test.py
index d5cbb24..3b91bba 100644
--- a/controller/fw/ldpc_decoder_test.py
+++ b/controller/fw/ldpc_decoder_test.py
@@ -16,8 +16,8 @@ args = parser.parse_args()
 
 lib = C.CDLL('./ldpc_decoder_test.so')
 
-n = 384
-nodes, bits = 6, 8
+n = 5*19
+nodes, bits = 17, 19
 H, G = pyldpc.make_ldpc(n, nodes, bits, systematic=False, seed=0)
 _1, bits_pos, _2 = scipy.sparse.find(H)
 _, k = G.shape
@@ -26,18 +26,23 @@ st = np.random.RandomState(seed=0)
 test_data = st.randint(0, 2, k)
 d = np.dot(G, test_data) % 2
 x = (-1) ** d
+x[29:] = 0
 
 bits_pos = bits_pos.astype(np.uint32)
 x = x.astype(np.int8)
 
 lib.decode.argtypes = [C.c_size_t, C.c_size_t, C.c_size_t, C.POINTER(C.c_size_t), C.POINTER(C.c_int8), C.POINTER(C.c_int8), C.c_uint]
+lib.get_message.argtypes = [C.c_size_t, C.c_size_t, C.POINTER(C.c_int8), C.POINTER(C.c_int8), C.POINTER(C.c_int8)]
 
 if args.reference:
     ref_out = test_decoder.decode(H, x, 3)
     print('decoder output:', ref_out, flush=True)
-    print('msg reconstruction:', pyldpc.get_message(G, ref_out))
-    print('reference decoder: ', np.all(np.equal(pyldpc.get_message(G, ref_out), test_data)), flush=True)
-    print(ref_out.dtype)
+    print('msg reconstruction:', test_decoder.get_message(G, ref_out))
+    print('reference decoder: ', np.all(np.equal(test_decoder.get_message(G, ref_out), test_data)), flush=True)
+    np.set_printoptions(linewidth=220)
+    print(test_data)
+    print(test_decoder.get_message(G, ref_out))
+    print(test_decoder.get_message(G, ref_out) ^ test_data)
 
 else:
     out = np.zeros(n, dtype=np.uint8)
@@ -48,6 +53,20 @@ else:
         out.ctypes.data_as(C.POINTER(C.c_int8)),
         25), flush=True)
     print('decoder output:', out)
-    print('msg reconstruction:', pyldpc.get_message(G, out))
-    print('decoder under test:', np.all(np.equal(pyldpc.get_message(G, out.astype(np.int64)), test_data)))
-    print(out.dtype)
+    print('msg reconstruction:', test_decoder.get_message(G, out.astype(np.int64)))
+    print('decoder under test:', np.all(np.equal(test_decoder.get_message(G, out.astype(np.int64)), test_data)))
+    np.set_printoptions(linewidth=220)
+    print(test_data)
+    print(test_decoder.get_message(G, out.astype(np.int64)))
+    G = G.astype(np.int8)
+    msg = np.zeros(k, dtype=np.int8)
+    lib.get_message(
+            n, k,
+            G.ctypes.data_as(C.POINTER(C.c_int8)),
+            out.astype(np.int8).ctypes.data_as(C.POINTER(C.c_int8)),
+            msg.ctypes.data_as(C.POINTER(C.c_int8)))
+    print(msg)
+    print(msg ^ test_data)
+
+print('codeword length:', len(x))
+print('data length:', len(test_data))
diff --git a/controller/fw/test_decoder.py b/controller/fw/test_decoder.py
index 806125b..8be5b02 100644
--- a/controller/fw/test_decoder.py
+++ b/controller/fw/test_decoder.py
@@ -43,23 +43,24 @@ def decode(H, y, snr, maxiter=100):
     Lr = np.zeros(shape=(m, n, n_messages))
 
     for n_iter in range(maxiter):
-        print(f'============================ iteration {n_iter} ============================')
+        #print(f'============================ iteration {n_iter} ============================')
         Lq, Lr, L_posteriori = _logbp_numba(bits_hist, bits_values, nodes_hist,
                                             nodes_values, Lc, Lq, Lr, n_iter)
-        print("Lq=", Lq.flatten())
-        print("Lr=", Lr.flatten())
+        #print("Lq=", Lq.flatten())
+        #print("Lr=", Lr.flatten())
         #print("L_posteriori=", L_posteriori.flatten())
-        print('L_posteriori=[')
-        for row in L_posteriori.reshape([-1, 16]):
-            for val in row:
-                cc = '\033[91m' if val < 0 else ('\033[92m' if val > 0 else '\033[94m')
-                print(f"{cc}{val: 012.6g}\033[38;5;240m", end=', ')
-            print()
+        #print('L_posteriori=[')
+        #for row in L_posteriori.reshape([-1, 16]):
+        #    for val in row:
+        #        cc = '\033[91m' if val < 0 else ('\033[92m' if val > 0 else '\033[94m')
+        #        print(f"{cc}{val: 012.6g}\033[38;5;240m", end=', ')
+        #    print()
         x = np.array(L_posteriori <= 0).astype(int)
 
         product = utils.incode(H, x)
 
         if product:
+            print(f'found, n_iter={n_iter}')
             break
 
     if n_iter == maxiter - 1:
@@ -83,13 +84,13 @@ def _logbp_numba(bits_hist, bits_values, nodes_hist, nodes_values, Lc, Lq, Lr,
     bits_counter = 0
     nodes_counter = 0
     for i in range(m):
-        print(f'=== i={i}')
+        #print(f'=== i={i}')
         ff = bits_hist[i]
         ni = bits_values[bits_counter: bits_counter + ff]
         bits_counter += ff
         for j_iter, j in enumerate(ni):
             nij = ni[:]
-            print(f'\033[38;5;240mj={j:04d}', end=' ')
+            #print(f'\033[38;5;240mj={j:04d}', end=' ')
 
             X = np.ones(n_messages)
             if n_iter == 0:
@@ -97,13 +98,13 @@ def _logbp_numba(bits_hist, bits_values, nodes_hist, nodes_values, Lc, Lq, Lr,
                     if nij[kk] != j:
                         lcv = Lc[nij[kk],0]
                         lcc = '\033[91m' if lcv < 0 else ('\033[92m' if lcv > 0 else '\033[94m')
-                        print(f'nij={nij[kk]:04d} Lc={lcc}{lcv:> 8f}\033[38;5;240m', end=' ')
+                        #print(f'nij={nij[kk]:04d} Lc={lcc}{lcv:> 8f}\033[38;5;240m', end=' ')
                         X *= np.tanh(0.5 * Lc[nij[kk]])
             else:
                 for kk in range(len(nij)):
                     if nij[kk] != j:
                         X *= np.tanh(0.5 * Lq[i, nij[kk]])
-            print(f'\n==== {i:03d} {j_iter:01d} {X[0]:> 8f}')
+            #print(f'\n==== {i:03d} {j_iter:01d} {X[0]:> 8f}')
             num = 1 + X
             denom = 1 - X
             for ll in range(n_messages):
-- 
cgit