Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
This program transforms the structure of the input edge list to the form required for PageRank (PR) algorithm in vertex-centric frameworks. PR needs the number of neighbors of the destination vertex be provided in the input file as the third argument of every edge in the edge-list (after the source vertex index and destination vertex index).
/*
* pr_input_provider.cpp
*
* Created on: Aug 31, 2015
* Author: Farzad Khorasani
*/
#include <iostream>
#include <string>
#include <cstring>
#include <fstream>
#include <algorithm>
#include <stdexcept>
#include <unordered_map>
#include <cstdlib>
template< typename idxT>
void PR_maker( std::ifstream& inFile, std::ofstream& outFile, const bool nonDirectedGraph ) {
/*
* Declare variables and functions required.
*/
std::unordered_map<idxT, idxT> mapper;
std::string line;
auto addEntryF = [&]( idxT key ) {
auto pos_index = mapper.find( key );
if( pos_index == mapper.end() ) { // The key does not exist. We need to add it.
std::pair<idxT, idxT> kvp( key, 1 );
mapper.insert( kvp );
}
else // The key does exist.
++( pos_index->second );
};
auto readLineIndices = [&]( idxT& firstIdx, idxT& secondIdx ) {
std::size_t pos = 2015;
firstIdx = static_cast< idxT >( std::stoul( line, &pos ) );
std::string sub_line;
sub_line = line.substr( ++pos );
secondIdx = static_cast< idxT >( std::stoul( sub_line, &pos ) );
};
auto entryToFileInserter = [&]( idxT lIdx, idxT rIdx ) {
auto pos_index = mapper.find( lIdx );
outFile << lIdx << "\t" << rIdx << "\t" << ( ( pos_index != mapper.end() ) ? ( pos_index->second ) : 0 ) << "\n";
};
/*
* Start the work.
*/
// Read the input graph line-by-line to collect data.
while( std::getline( inFile, line ) ) {
if( line[0] < '0' || line[0] > '9' ) // Skipping any line blank or starting with a character rather than a number.
continue;
idxT firstIndex, secondIndex;
readLineIndices( firstIndex, secondIndex );
addEntryF( secondIndex );
if( nonDirectedGraph ) addEntryF( firstIndex );
}
// Restart the file pointer to its beginning.
inFile.clear();
inFile.seekg(0, std::ios::beg);
// Read the input graph line-by-line again and insert the third-column for each entry to the output file.
while( std::getline( inFile, line ) ) {
if( line[0] < '0' || line[0] > '9' ) { // Skipping any line blank or starting with a character rather than a number.
outFile << line << "\n";
continue;
}
idxT firstIndex, secondIndex;
readLineIndices( firstIndex, secondIndex );
entryToFileInserter( firstIndex, secondIndex );
if( nonDirectedGraph ) entryToFileInserter( secondIndex, firstIndex );
}
}
// Opening files safely.
template <typename T_file>
void openFileToAccess( T_file& inputF, const char* fileName ) {
inputF.open( fileName );
if( !inputF )
throw std::runtime_error( "Failed to open specified file." );
}
int main ( int argc, char ** argv )
{
const std::string usage =
"\tRequired command line arguments:\n\
-Input file: E.g., --input in.txt\n\
Additional arguments:\n\
-Output file (default: out.txt). E.g., --output myout.txt\n\
-Is the input graph directed (default:yes). To specify it as undirected: --undirected\n";
std::ofstream outFile;
std::ifstream inFile;
bool nonDirectedGraph = false; // By default, the graph is directed.
try{
// Getting required input parameters.
for( int iii = 1; iii < argc; ++iii )
if( !strcmp( argv[iii], "--input" ) && iii != argc-1 /*is not the last one*/)
openFileToAccess< std::ifstream >( inFile, argv[iii+1] );
else if( !strcmp( argv[iii], "--output" ) && iii != argc-1 /*is not the last one*/)
openFileToAccess< std::ofstream >( outFile, argv[iii+1] );
else if( !strcmp(argv[iii], "--undirected"))
nonDirectedGraph = true;
if( !inFile.is_open() )
throw std::runtime_error( "The input file has not been specified." );
if( !outFile.is_open() )
openFileToAccess< std::ofstream >( outFile, "out.txt" );
// Start the work.
std::cout << "Starting the work ..." << std::endl;
using vertexIndexType = unsigned int;
PR_maker<vertexIndexType>( inFile, outFile, nonDirectedGraph );
std::cout << "Done.\n";
}
catch( const std::exception& strException ) {
std::cerr << "Initialization Error: " << strException.what() << "\n";
std::cerr << "Usage: " << usage << std::endl << "Exiting." << std::endl;
return( EXIT_FAILURE );
}
catch(...) {
std::cerr << "An exception has occurred." << std::endl;
return( EXIT_FAILURE );
}
return( EXIT_SUCCESS );
}
Owner

farkhor commented Aug 31, 2015

This program uses C++11 features and libraries. Please compile it with a C++11 compiler.

Owner

farkhor commented Sep 1, 2015

Also, please note that if the input graph is non-directed for the above program, the output graph will be a directed version. To make a non-directed output graph from a non-directed input graph, you should comment out line 77 and rebuild the program.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment