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Decrease memory footprint of stack and improve stack decoder efficiency.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@5723 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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@ -32,7 +32,7 @@ int jelinek(
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unsigned char *symbols, /* Raw deinterleaved input symbols */
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unsigned int nbits, /* Number of output bits */
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unsigned int stacksize,
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struct node *stack,
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struct snode *stack,
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int mettab[2][256], /* Metric table, [sent sym][rx symbol] */
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unsigned int maxcycles)/* Decoding timeout in cycles per bit */
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{
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@ -51,11 +51,11 @@ int jelinek(
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}
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// zero the stack
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memset(stack,0,stacksize*sizeof(struct node));
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memset(stack,0,stacksize*sizeof(struct snode));
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// initialize the loop variables
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unsigned int lsym, highbit, ntail=31;
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uint64_t encstate=0, encstate_highbits=0;
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unsigned int lsym, ntail=31;
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uint64_t encstate=0;
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unsigned int nbuckets=1000;
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unsigned int low_bucket=nbuckets-1; //will be set on first run-through
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unsigned int high_bucket=0;
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@ -72,20 +72,22 @@ int jelinek(
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/********************* Start the stack decoder *****************/
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for (i=1; i <= ncycles; i++) {
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#ifdef DEBUG
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printf("***stackptr=%d, depth=%d, gamma=%d, encstate=%lx, encstate_highbits=%lx\n",
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stackptr, depth, gamma, encstate, encstate_highbits);
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printf("***stackptr=%ld, depth=%d, gamma=%d, encstate=%lx, bucket %d, low_bucket %d, high_bucket %d\n",
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stackptr, depth, gamma, encstate, bucket, low_bucket, high_bucket);
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#endif
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// save the highbit of the encoder state and shift to the left, bringing
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// in a 0. This is the encoder state of the daughter node connected
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// to the current node by the "0" branch
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highbit=encstate>>63;
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encstate=encstate<<1;
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if( depth > 63 ) {
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encstate_highbits=(encstate_highbits<<1)|highbit;
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// no need to store more than 7 bytes (56 bits) for encoder state because
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// only 50 bits are not 0's.
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if( depth < 56 ) {
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encstate=encstate<<1;
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}
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// get channel symbols associated with the 0 branch
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ENCODE(lsym,encstate); /* 0-branch (LSB is 0) */
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if( depth < 56 ) {
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ENCODE(lsym,encstate);
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} else {
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ENCODE(lsym,encstate<<(depth-55));
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}
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// lsym are the 0-branch channel symbols and 3^lsym are the 1-branch
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// channel symbols (due to a special property of our generator polynomials)
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totmet0 = gamma+metrics[depth][lsym]; // total metric for 0-branch daughter node
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@ -98,7 +100,6 @@ int jelinek(
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// place the 0 node on the stack, overwriting the parent (current) node
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stack[ptr].encstate=encstate;
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stack[ptr].encstate_highbits=encstate_highbits;
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stack[ptr].gamma=totmet0;
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stack[ptr].depth=depth;
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stack[ptr].jpointer=buckets[bucket];
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@ -123,14 +124,13 @@ int jelinek(
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if( bucket < low_bucket ) low_bucket=bucket;
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stack[ptr].encstate=encstate+1;
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stack[ptr].encstate_highbits=encstate_highbits;
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stack[ptr].gamma=totmet1;
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stack[ptr].depth=depth;
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stack[ptr].jpointer=buckets[bucket];
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buckets[bucket]=ptr;
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}
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// pick off the latest entry from the high bucket
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// pick off the latest entry from the high bucket
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while( buckets[high_bucket] == 0 ) {
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high_bucket--;
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}
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@ -139,7 +139,6 @@ int jelinek(
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depth=stack[ptr].depth;
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gamma=stack[ptr].gamma;
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encstate=stack[ptr].encstate;
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encstate_highbits=stack[ptr].encstate_highbits;
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// we are done if the top entry on the stack is at depth nbits
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if (depth == nbits) {
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@ -149,22 +148,15 @@ int jelinek(
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*cycles = i+1;
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*metric = gamma; /* Return final path metric */
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// printf("cycles %d stackptr=%d, depth=%d, gamma=%d, encstate=%lx, encstate_highbits=%lx\n",
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// *cycles, stackptr, depth, *metric, encstate, encstate_highbits);
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// 81 bits is an awkward number... shift everything to the right by one
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// bit first
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int highbit_lsb=encstate_highbits&(0x0000000000000001);
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encstate_highbits=encstate_highbits>>1;
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encstate=encstate>>1;
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if( highbit_lsb == 1 ) {
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encstate=encstate|(0x8000000000000000);
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}
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//copy data to output buffer
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data[0]=encstate_highbits>>8;
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data[1]=encstate_highbits&(0x00000000000000ff);
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for (i=2; i<10; i++) {
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data[i]=(encstate>>(56-(i-2)*8))&(0x00000000000000ff);
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// printf("cycles %d stackptr=%d, depth=%d, gamma=%d, encstate=%lx\n",
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// *cycles, stackptr, depth, *metric, encstate);
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for (i=0; i<7; i++) {
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data[i]=(encstate>>(48-i*8))&(0x00000000000000ff);
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}
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for (i=7; i<11; i++) {
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data[i]=0;
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}
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if(*cycles/nbits >= maxcycles) //timed out
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@ -3,15 +3,14 @@
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#include <stdint.h>
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struct node {
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struct snode {
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uint64_t encstate; // Encoder state
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uint64_t encstate_highbits; // least significant 50 bits are the data
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int gamma; // Cumulative metric to this node
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unsigned int depth; // depth of this node
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unsigned int jpointer;
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};
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struct node *stack;
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struct snode *stack;
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int jelinek(unsigned int *metric,
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unsigned int *cycles,
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@ -19,7 +18,7 @@ int jelinek(unsigned int *metric,
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unsigned char *symbols,
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unsigned int nbits,
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unsigned int stacksize,
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struct node *stack,
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struct snode *stack,
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int mettab[2][256],
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unsigned int maxcycles);
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@ -698,7 +698,7 @@ int main(int argc, char *argv[])
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}
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if( stackdecoder ) {
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stack=malloc(stacksize*sizeof(struct node));
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stack=malloc(stacksize*sizeof(struct snode));
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}
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if( optind+1 > argc) {
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