main.cpp

斯坦福Energy211/CME211课《c++编程——地球科学科学家和工程师》的课件

// This program demonstrates command-line arguments

#include <iostream>
#include <sstream>
#include <fstream>
#include "linsys.h"

using namespace std;

const char szUsage[] = {
	"Usage: custom_solve [-tol eps] [-method ge|jacobi|gs|sor] [-maxiter n] [-w val] datafile\n"
} ;

void UsageError( const string& sMesg ) {
	string total_mesg = "Error: " + sMesg + "\n" + szUsage;
	throw runtime_error( total_mesg.c_str() );
}

int main( int argc, char *argv[] )
{	
	try {
		
		// default values
		double tol = 1e-8;
		bool direct = true;
		int maxiter = 100;
		double w = 1.0;
		LinearSystem::IterMethod m = LinearSystem::MethodJacobi;
	
		string filename;
		
		// this points to the current argument
		char **cp;
		// iterate through arguments, skipping over
		// first one before we begin
		for ( cp = ++argv, --argc; argc > 0; 
				++cp, --argc ) {
			// all arguments begin with a -, except
			// for the name of the input file
			if ( **cp == '-' ) {
				string s = ++*cp;
				if ( s == "tol" ) {
					++cp;
					--argc;
					istringstream is( *cp );
					is >> tol;
				}
				else if ( s == "w" ) {
					++cp;
					--argc;
					istringstream is( *cp );
					is >> w;
				}
				else if ( s == "method" ) {
					++cp;
					--argc;
					string smethod = *cp;
					if ( smethod == "ge" )
						direct = true;
					else if ( smethod == "jacobi" ) {
						direct = false;
						m = LinearSystem::MethodJacobi;
					}
					else if ( smethod == "gs" ) {
						direct = false;
						m = LinearSystem::MethodGaussSeidel;
					}
					else if ( smethod == "sor" ) {
						direct = false;
						m = LinearSystem::MethodSOR;
					}
					else
						UsageError( "invalid iterative method" );
				}
				else if ( s == "maxiter" ) {
					++cp;
					--argc;
					istringstream is( *cp );
					is >> maxiter;
				}
				else {
					string sMesg = string( "Invalid option: " ) + *cp;
					UsageError( sMesg );
				}
			}
			else
				filename = *cp;
		}
		
		// this argument is required
		if ( filename.size() == 0 )
			UsageError( "no filename specified" );
	
		// open file, making sure it exists
		ifstream datafile( filename.c_str() );
		if ( datafile.fail() ) {
			string mesg = string( "file " ) + *cp + 
				" does not exist";
			UsageError( mesg );
		}
	
		Matrix A;
		ColVector b;

		// read system
		datafile >> A;
		cout << "A = \n" << A;
		datafile >> b;
		cout << "b = \n" << A;
	
		// and solve it, in manner prescribed
		// by command-line arguments
		LinearSystem S( A );
		ColVector x;
	
		if ( direct )
			x = S.DirectSolve( b );
		else {
			S.SetMaxIter( maxiter );
			S.SetTol( tol );
			x = S.IterativeSolve( b, m, w );
		}
		
		cout << "x = \n" << x;
		
	}
	catch( runtime_error e ) {
		// any exception, due to incorrect usage or
		// a problem solving the system, is caught here
		cout << e.what();
	}
		
	return 0;
}