[MN-dev] [mndiff]: r149 - in trunk/noe: ldpc.c ldpc.h

[michael]

Author: michael
Date: Sun Apr 12 05:22:04 2009
New Revision: 149

Log:
Optional support for fast to encode matrixes.

Modified:
   trunk/noe/ldpc.c
   trunk/noe/ldpc.h

Modified: trunk/noe/ldpc.c
==============================================================================
--- trunk/noe/ldpc.c	Sat Apr 11 23:42:47 2009	(r148)
+++ trunk/noe/ldpc.c	Sun Apr 12 05:22:04 2009	(r149)
@@ -34,7 +34,7 @@
 #define MAX_NZC 32
 
 typedef struct LDPCContext{
-    unsigned int (*parity_matrix)[2][MAX_NZC];
+    int (*parity_matrix)[2][MAX_NZC];
     int (*inv_matrix)[2];
     int parity_len;
     int data_len;
@@ -151,6 +151,8 @@ LDPCContext *EXT(initLDPC)(int data_len,
         memset(tab, 0, parity_len);
         for(j=0; j<nzc; j++){
             int minrow=999999;
+
+            if(i<data_len || seed>0){
             for(y=0; y<parity_len; y++){
                 if(row[y] < minrow)
                     minrow= row[y];
@@ -158,6 +160,13 @@ LDPCContext *EXT(initLDPC)(int data_len,
             do{
                 y= get_random(&kiss)%parity_len;
             }while(tab[y] || (row[y] > minrow + (SIZE == 2)));
+            }else{
+                y= i + j - data_len;
+                if(y >= parity_len){
+                    c->parity_matrix[i][0][j] = -1;
+                    continue;
+                }
+            }
             tab[y]=1;
             c->parity_matrix[i][0][j] = y;
             c->parity_matrix[i][1][j] = EXT(log)[get_random(&kiss)%(SIZE-1)+1];
@@ -222,8 +231,10 @@ int EXT(init_matrixLDPC)(LDPCContext *c,
         x= erasure_pos[i];
         for(j=0; j<nzc; j++){
             y= c->parity_matrix[x][0][j];
+            if(y>=0){
             inv_matrix[i + y*2*parity_len]= EXT(exp)[c->parity_matrix[x][1][j]];
             row_weight[y]++;
+            }
         }
         col_weight[i]= nzc;
     }
@@ -266,8 +277,10 @@ int EXT(decodeLDPC)(LDPCContext *c, LDPC
         unsigned int v= code[i];
         for(j=0; j<c->nzc; j++){
             int y= c->parity_matrix[i][0][j] + c->parity_len;
+            if(y>=c->parity_len){
             int p= -EXT(exp)[c->parity_matrix[i][1][j]];
             syndrom[y]^= p & v;
+            }
         }
     }
 
@@ -288,8 +301,10 @@ int EXT(decodeLDPC)(LDPCContext *c, LDPC
         unsigned int v= EXT(log)[ code[i] ];
         for(j=0; j<c->nzc; j++){
             int y= c->parity_matrix[i][0][j] + c->parity_len;
+            if(y>=c->parity_len){
             int p= c->parity_matrix[i][1][j];
             syndrom[y]= sum(syndrom[y], EXT(exp)[p + v]);
+            }
         }
     }
 

Modified: trunk/noe/ldpc.h
==============================================================================
--- trunk/noe/ldpc.h	Sat Apr 11 23:42:47 2009	(r148)
+++ trunk/noe/ldpc.h	Sun Apr 12 05:22:04 2009	(r149)
@@ -26,6 +26,8 @@ struct LDPCContext;
 
 /**
  *
+ * @param seed if 0 then a matrix will be generated that can be encoded quicker
+ *             at the expense of worse error recovery capabilities.
  * @param nzc number of non zero elements per column, 0 means choose automatically.
  */
 struct LDPCContext *EXT(initLDPC)(int data_len, int parity_len, uint32_t seed, int nzc);