graph_preprocessor.cpp

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#include <iostream>
#include <string>
#include <utility>
#include <map>
#include <cstdio>
#include <vector>
#include <sys/file.h>
#include <stdint.h>
#include <algorithm>
 
 
using namespace std;
 
template<typename _ForwardIterator>
bool is_sorted(_ForwardIterator __first, _ForwardIterator __last)
{
    if (__first == __last)
        return true;
 
    _ForwardIterator __next = __first;
    for (++__next; __next != __last; __first = __next, ++__next)
        if (*__next < *__first)
            return false;
    return true;
}
 
template<typename _ForwardIter, typename T>
void iota(_ForwardIter __first, _ForwardIter __last, T __value)
{
    while (__first != __last)
        *__first++ = __value++;
}
 
 
int main()
{
    int64_t nverts = 133633040;
    int64_t nedges = 5507679822;
    FILE * infp = fopen("uk-union.graph.bin", "rb");
    
    uint32_t * gen_edges = new uint32_t[2*nedges];
    fread(gen_edges, 2*nedges, sizeof(uint32_t), infp);
    cout << "Read data" << endl;    
 
    vector< vector<uint32_t> > adj(nverts);
    vector< uint32_t > shuffler(nverts);
    iota(shuffler.begin(), shuffler.end(), static_cast<uint32_t>(0));
    random_shuffle ( shuffler.begin(), shuffler.end() );
 
    for(int64_t i=0; i< 2*nedges; i+=2)
    {
         adj[shuffler[gen_edges[i]]].push_back(shuffler[gen_edges[i+1]]);
         adj[shuffler[gen_edges[i+1]]].push_back(shuffler[gen_edges[i]]);
    }
    cout << "Made adjacencies" << endl;
    delete [] gen_edges;
    
    FILE * outp = fopen("uk-union.symmetric.bin", "wb");
 
    int64_t count = 0;
    for(int64_t i=0; i< nverts; ++i)
    {
        uint32_t edge[2];
        edge[0] = i;
        sort(adj[i].begin(), adj[i].end());
        vector<uint32_t>::iterator p_end = unique(adj[i].begin(), adj[i].end()); // move consecutive duplicates past the end, store the new end
        for(vector<uint32_t>::iterator p = adj[i].begin(); p != p_end; ++p)
        {
            edge[1] = *p;
            fwrite(edge, 1, 2*sizeof(uint32_t), outp);
            ++count;
        }
    }
    fclose(outp);
    cout << "Number of edges: " << count << endl;
}