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456 lines
12 KiB
C++
456 lines
12 KiB
C++
/*
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* =====================================================================================
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*
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* Filename: ldgm-session-cpu.cpp
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*
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* Description: CPU implementation of LDGM coding
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*
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* Version: 1.0
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* Created: 04/12/2012 01:21:07 PM
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* Revision: none
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* Compiler: gcc
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*
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* Author: Milan Kabat (), kabat@ics.muni.cz
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* Organization:
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*
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* =====================================================================================
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <emmintrin.h>
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#include <string.h>
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#include <time.h>
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#include "ldgm-session-cpu.h"
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#include "timer-util.h"
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using namespace std;
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char*
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xor_using_sse (char* source, char* dest, int packet_size)
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{
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//First, do as many 128-bit XORs as possible
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int iter_bytes_16 = 0;
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int iter_bytes_4 = 0;
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int iter_bytes_1 = 0;
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iter_bytes_16 = (packet_size/16)*16;
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if ( iter_bytes_16 > 0)
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{
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// printf ( "iter_bytes: %d\n", iter_bytes );
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__m128i* wrd_ptr = (__m128i *) source;
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__m128i* wrd_end = (__m128i *) (source + iter_bytes_16);
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__m128i* dst_ptr = (__m128i *) dest;
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// printf ( "wrd_ptr address: %p\n", wrd_ptr );
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do
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{
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__m128i xmm1 = _mm_loadu_si128(wrd_ptr);
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__m128i xmm2 = _mm_loadu_si128(dst_ptr);
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xmm1 = _mm_xor_si128(xmm1, xmm2); // XOR 4 32-bit words
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_mm_storeu_si128(dst_ptr, xmm1);
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++wrd_ptr;
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++dst_ptr;
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} while (wrd_ptr < wrd_end);
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}
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//Check, whether further XORing is necessary
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if ( iter_bytes_16 < packet_size )
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{
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char *mark_source = source + iter_bytes_16;
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char *mark_dest = dest + iter_bytes_16;
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iter_bytes_4 = ((packet_size - iter_bytes_16)/4)*4;
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for ( int i = 0; i < (packet_size - iter_bytes_16)/4; i++)
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{
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int *s = ((int*) mark_source) + i;
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int *d = ((int*) mark_dest) + i;
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*d ^= *s;
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}
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mark_source += iter_bytes_4;
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mark_dest += iter_bytes_4;
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iter_bytes_1 = packet_size - iter_bytes_16 - iter_bytes_4;
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for ( int i = 0; i < iter_bytes_1; i++)
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{
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*(mark_dest + i) ^= *(mark_source+i);
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}
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}
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// printf ( "XORed: %d bytes using SSE, %d bytes as ints and %d bytes byte-per-byte.\n",
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// iter_bytes_16, iter_bytes_4, iter_bytes_1);
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return dest;
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}
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void
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LDGM_session_cpu::encode ( char* data_ptr, char* parity_ptr )
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{
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// start encoding
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// printf ( "packet_size: %d\n", this->packet_size );
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void *ppacket;
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char *parity_packet;
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for ( int m = 0; m < param_m; ++m) {
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int e = posix_memalign(&ppacket, 16, packet_size);
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if (e)
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{
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printf ( "Error while using posix_memalign\n" );
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return;
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}
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// printf ( "m: %d\n", m );
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memset(ppacket, 0, packet_size);
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parity_packet = (char*)ppacket;
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// printf ( "max w: %d\n", max_row_weight );
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//Find out which packets to XOR
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for ( int k = 0; k < max_row_weight+2; ++k) {
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int idx = pcm[m*(max_row_weight+2) + k];
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// printf ( "adept: %d\n", idx );
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if (idx > -1 && idx < param_k) {
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// printf ( "xoring idx: %d\n", idx );
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char *ptr = data_ptr + idx*packet_size;
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parity_packet = xor_using_sse(ptr, parity_packet, packet_size);
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}
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}
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//Apply inverted staircase matrix
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if( m > 0) {
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char *prev_parity = parity_ptr + (m-1)*packet_size;
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parity_packet = xor_using_sse(prev_parity, parity_packet, packet_size);
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}
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//Add the new parity packet to overall parity
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memcpy ( parity_ptr + m*packet_size, parity_packet, packet_size );
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free(ppacket);
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}
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return ;
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} /* ----- end of method LDGM_session_cpu::encode ----- */
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void
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LDGM_session_cpu::free_out_buf ( char *buf)
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{
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if ( buf != NULL )
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free(buf);
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}
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void
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LDGM_session_cpu::encode_naive ( char* data_ptr, char* parity_ptr )
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{
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// start encoding
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void *ppacket;
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char *parity_packet;
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for ( int m = 0; m < param_m; ++m) {
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int e = posix_memalign(&ppacket, 16, packet_size);
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if (e)
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{
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printf ( "Error while using posix_memalign\n" );
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return;
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}
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memset(ppacket, 0, packet_size);
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parity_packet = (char*)ppacket;
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//Find out which packets to XOR
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for ( int k = 0; k < max_row_weight+2; ++k) {
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int idx = pcm[m*(max_row_weight+2) + k];
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if (idx > -1 && idx < param_k) {
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char *ptr = data_ptr + idx*packet_size;
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// parity_packet = xor_using_sse(ptr, parity_packet, packet_size);
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for ( int i = 0; i < packet_size; i++)
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parity_packet[i] ^= *(ptr+i);
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}
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}
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//Apply inverted staircase matrix
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if( m > 0) {
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char *prev_parity = parity_ptr + (m-1)*packet_size;
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// parity_packet = xor_using_sse(prev_parity, parity_packet, packet_size);
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for ( int i = 0; i < packet_size; i++)
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parity_packet[i] ^= *(prev_parity+i);
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}
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//Add the new parity packet to overall parity
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memcpy ( parity_ptr + m*packet_size, parity_packet, packet_size );
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free(ppacket);
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}
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return ;
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} /* ----- end of method LDGM_session_cpu::encode ----- */
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void iterate ( Tanner_graph *g);
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char*
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LDGM_session_cpu::decode_frame ( char* received, int buf_size, int* frame_size,
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std::map<int, int> valid_data )
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{
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// printf ( "buf_size: %d\n", buf_size );
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Tanner_graph graph;
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int p_size = buf_size/(param_m+param_k);
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this->packet_size = p_size;
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// printf ( "p_size %d\n", p_size );
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graph.set_data_size(p_size);
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Timer_util timer;
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int i;
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int index = 0;
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// while ( i < (param_k + param_m)*p_size)
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// {
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// printf ( "%2d|", (unsigned char)received[i++] );
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// }
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//one variable node per each data packet in block K
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for ( i = 0; i < param_k; ++i )
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graph.add_node(Node::variable_node, index++, received + i*p_size);
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//one variable node per each parity packet in block M
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for ( i = 0; i < param_m; ++i)
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graph.add_node(Node::variable_node, index++, received + (i + param_k)*p_size);
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//one constraint node per each row of generation matrix
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for ( i = 0; i < param_m; ++i)
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graph.add_node(Node::constraint_node, index++, NULL);
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create_edges(&graph);
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// printf("Graph created in: %.3f s\n", t);
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/* printf ( "graf\n" );
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* for(map<int, Node>::iterator it = graph.nodes.begin(); it != graph.nodes.end(); ++it) {
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* Node n = it->second;
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* for ( int i = 0; i < p_size; ++i)
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* printf("%2d|", *(unsigned char *)(n.getDataPtr() + i));
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* printf ( "---\n" );
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* }
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*/
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/* for(map<int, Node>::iterator it = graph.nodes.begin(); it != graph.nodes.end(); ++it) {
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* Node n = it->second;
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* printf ( "neigbours of %d (count %lu): ", it->first, (it->second).neighbours.size() );
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* for(vector<int>::iterator itr = n.neighbours.begin(); itr != n.neighbours.end(); ++itr)
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* printf ( "%d ", *itr );
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* printf ( "\n" );
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* }
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*/
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//We need to merge intervals in the valid data vector
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map <int, int> merged_intervals;
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map<int,int>::iterator map_it;
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if ( valid_data.size() != 0 )
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{
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for ( map_it = valid_data.begin(); map_it != valid_data.end(); )
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{
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int start = map_it->first;
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int length = map_it->second;
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while ( start + length == (++map_it)->first )
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length += map_it->second;
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merged_intervals.insert ( pair<int, int> (start, length) );
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}
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}
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/* printf ( "Valid data: \n" );
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* for ( map_it = valid_data.begin(); map_it != valid_data.end(); ++map_it)
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* {
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* printf ( "|%d-%d| ", map_it->first, map_it->second );
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* }
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* printf ( "\n" );
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*
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* printf ( "Merged intervals: \n" );
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* for ( map_it = merged_intervals.begin(); map_it != merged_intervals.end(); ++map_it)
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* {
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* printf ( "|%d-%d| ", map_it->first, map_it->second );
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* }
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* printf ( "\n" );
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*
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*/
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map<int, Node>::iterator it;
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if ( merged_intervals.size() != 0)
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{
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it = graph.nodes.find(0);
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while (it != graph.nodes.find(param_k+param_m)) {
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(*it).second.setDone(false);
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int node_offset = (*it).second.getDataPtr() - received;
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// printf ( "offset: %d\n", node_offset );
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map_it = merged_intervals.begin();
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//Find the offset in valid data which is equal, or the first offset which is
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//lower than node offset
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bool found = false;
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while ( (map_it->first <= node_offset) && map_it != merged_intervals.end() )
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{
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map_it++;
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found = true;
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}
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if ( map_it->first > 0 )
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map_it--;
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//Next, find out if some interval covers this symbol
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if ( found && (map_it->first + map_it->second) >=
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(node_offset + p_size) )
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{
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(*it).second.setDone(true);
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// printf ( "setting node %d with offset %d and size %d as done\n", it->first,
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// node_offset, p_size);
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}
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++it;
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}
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}
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int not_done = 0;
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for ( it = graph.nodes.begin(); it != graph.nodes.find(param_k); it++)
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{
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if ( !it->second.isDone())
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{
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memset(it->second.getDataPtr(), 0, p_size);
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// printf ( "resetting node: %d\n", it->first );
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not_done++;
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}
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}
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// printf ( "not done: %d\n", not_done );
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/* srand(time(NULL));
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* for ( int j = 0; j < 100; j++)
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* {
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* it = graph.nodes.find(rand()%(param_k+param_m));
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* (*it).second.setDone(false);
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* }
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*/
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int iter = 0;
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while ( needs_decoding(&graph) && iter < 4) {
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// printf ( "iteratin\n" );
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iterate(&graph);
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iter++;
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}
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// printf("decoding process: %.3f s\n", t);
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//printf ( "iterations: %d\n", iter );
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int undecoded = 0;
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it = graph.nodes.find(0);
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while ( it != graph.nodes.find(param_k) ) {
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if (!(*it).second.isDone())
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undecoded++;
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++it;
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}
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// printf ( "Number of not recovered data packets: %d\n", undecoded );
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// printf("rest: %.3f s\n", t);
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if ( undecoded == 0 )
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{
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union int_bytes {
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unsigned int number;
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unsigned char bytes[4];
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};
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union int_bytes fs;
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memcpy(&(fs.bytes), received, 4);
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*frame_size = fs.number;
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}
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else
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*frame_size = 0;
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return received+4;
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} /* ----- end of method LDGM_session_cpu::decode ----- */
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void
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LDGM_session_cpu::iterate ( Tanner_graph *graph )
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{
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map<int, Node>::iterator it_c;
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vector<int> vec;
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static int recovered = 0;
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//select the first constraint node
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it_c = graph->nodes.find ( param_k + param_m );
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//iterate through constraint nodes
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while ( it_c != graph->nodes.end() ) {
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//iterate the node's neighbours to find out how many of them are not decoded
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map<int, Node>::iterator it_v;
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for(vector<int>::iterator j = it_c->second.neighbours.begin();
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j != it_c->second.neighbours.end(); ++j) {
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it_v = graph->nodes.find(*j);
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if ( !it_v->second.isDone() )
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vec.push_back(*j);
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}
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// printf ( "node %d has %d undecoded neighbours\n", it_c->first, vec.size() );
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//we can restore the missing packet
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if ( vec.size() == 1)
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{
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int r_index = vec.front();
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// if ( r_index == 0 )
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// {
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// printf ( "repairing first block\n" );
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// }
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it_v = graph->nodes.find(r_index);
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memset(it_v->second.getDataPtr(), 0, packet_size);
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char *r_data = it_v->second.getDataPtr();
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//find other nodes connected to this constraint node and XOR their values
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int count = 0;
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for(vector<int>::iterator j = it_c->second.neighbours.begin();
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j != it_c->second.neighbours.end(); ++j)
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{
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if ( *j != r_index )
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{
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// printf ( "decode, packet_size: %d\n", packet_size );
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char *g_data = (graph->nodes.find(*j))->second.getDataPtr();
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//XOR
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xor_using_sse(g_data, r_data, packet_size);
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count++;
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}
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}
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/* //validate recovered packet
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* for ( int i = 0; i < param_k; ++i) {
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* if(!memcmp(r_data, lost_ptr + i*packet_size, packet_size)) {
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* printf ( "packet ok\n" );
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* break;
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* }
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* }
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*/
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if ( count > 0 )
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it_v->second.setDone(true);
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recovered++;
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/* printf ( "restored data: \n" );
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* for ( int i = 0; i < packet_size; ++i)
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* printf ( "%2d|", (unsigned char)(*(it_v->second.getDataPtr() + i)) );
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* printf ( "---\n" );
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*/
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}
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vec.clear();
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++it_c;
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}
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// printf ( "recovered: %d\n", recovered );
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return;
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}
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