Gauss-seidel and ASCII

[Brandybuck]

I might still need some help with the rest of the assignment. So I'm not going to set this to solved yet, but I'm taking a break. my brain hurts and my stomach is empty

[Brandybuck]

hey so the code was running in virtual studio, but I need it to run with g++ I took out the #include "stdafx.h"

I keep getting the error

os@os:~$ g++ gaussian.cpp
g++: error: gaussian.cpp: No such file or directory
g++: fatal error: no input files
compilation terminated.

Its saved on the desktop of a debian OS and I've double checked the upper lower case letters. i've renamed it a few times and tried running that.

#include<iostream>
#include<cmath>

int main()
{
	double C[3], cL, i;
	double a[3][4] = { { 15, -3, -1, 3800 },
	{ -3, 18, -6, 1200 },
	{ -4, -3, 12, 2350 } };
	C[0] = a[0][3] / a[0][0];
	C[1] = a[1][3] / a[1][1];
	C[2] = a[2][3] / a[2][2];
	i = 1;
	cL = 1000;
	while (true)
	{
		if (i <= cL)
		{
			C[0] = (a[0][3] - C[1] * a[0][1] - C[2] * a[0][2]) / a[0][0];
			C[1] = (a[1][3] - C[0] * a[1][0] - C[2] * a[1][2]) / a[1][1];
			C[2] = (a[2][3] - C[0] * a[2][0] - C[1] * a[2][1]) / a[2][2];
			i = i + 1;
		}
		else
		{
			std::cout << C[0];
			std::cout << C[1];
			std::cout << C[2];
			break;
		}
	}
}

[Brandybuck]

lol it decided to work

[Brandybuck]

This is the next step I'm working on

After the function is called it will write the data to an ASCII file name results.dat in the following format:

any suggestions are helpful :)

[jonnin]

roughly.

ofstream ofs;
ofs.open("targetfile.txt");

ofs << what goes into file; //works exactly like cout.

ofs.close();

you can see the file on the unix console quickly with
cat filename

[Brandybuck]

I got the code to print an ASCII file with the correct answers, but I'm having difficulty getting it to read an ASCII file now

#include<iostream>
#include<cmath>
#include<cstdio>
#include<stdio.h>
#include<fstream>

using namespace std;

int main()
{
	double C[3], er, er0, a[3][4];
	FILE* fp;
	fp = fopen("datafile.dat", "r+");
	fscanf(fp, " %1f ", &a[3][4]);
	
	C[0] = a[0][3] / a[0][0];
	C[1] = a[1][3] / a[1][1];
	C[2] = a[2][3] / a[2][2];
	er=5e-10;
	er0=0;
	int n;

	while (n)
	{

			C[0] = (a[0][3] - C[1] * a[0][1] - C[2] * a[0][2]) / a[0][0];
			C[1] = (a[1][3] - C[0] * a[1][0] - C[2] * a[1][2]) / a[1][1];
			C[2] = (a[2][3] - C[0] * a[2][0] - C[1] * a[2][1]) / a[2][2];
			
			if ( ((C[1]-er0)/C[1])<er)
			{
				n=0;
			}
			er0=C[1];
	}


			FILE *fp1;
			fp1 = fopen("results.dat","w+");
			fprintf(fp1,"C[1] = %8.4f \n",C[0]);
			fprintf(fp1,"C[2] = %8.4f \n",C[1]);
			fprintf(fp1,"C[3] = %8.4f \n",C[2]);
}

the program runs without any errors but the answers are completly off

[Brandybuck]

This is the code I made to write an ASCII file names datafile.dat

#include <iostream>

#include <stdio.h>

int main ()

{

double a[3][4];

int i,j;

a[0][0]=15;

a[0][1]=-3;

a[0][2]=-1;

a[0][3]=3800;

a[1][0]=-3;

a[1][1]=18;

a[1][2]=-6;

a[1][3]=1200;

a[2][0]=-4;

a[2][1]=-3;

a[2][2]=12;

a[2][3]=2350;

FILE *fp;

fp = fopen("datafile.dat","w+");

for(i=0;i<3;i++)

{

for(j=0;j<4;j++)

{ fprintf(fp,"%.0f ",a[i][j]);

}

fprintf(fp,"\n");

}

fclose(fp);

return(0);

}

This code runs fine, I'm just uploading it as a reference for you.

[Brandybuck]

I changed it to this code and I'm getting the same wrong answer.

#include<iostream>
#include<cmath>
#include<cstdio>
#include<stdio.h>
#include<fstream>

using namespace std;

int main()
{
	double C[3], er, er0, a[3][4];
	FILE* fp;
	fp = fopen("datafile.dat", "r+");
	fscanf(fp, " %1f, %1f, %1f, %1f, %1f, %1f, %1f, %1f, %1f, %1f, %1f, %1f, ", &a[0][0], &a[0][1], &a[0][2], &a[0][3], &a[1][0], &a[1][1], &a[1][2], &a[1][3], &a[2][0], &a[2][1], &a[2][2], &a[2][3]);
	
	C[0] = a[0][3] / a[0][0];
	C[1] = a[1][3] / a[1][1];
	C[2] = a[2][3] / a[2][2];
	er=5e-10;
	er0=0;
	int n;

	while (n)
	{

			C[0] = (a[0][3] - C[1] * a[0][1] - C[2] * a[0][2]) / a[0][0];
			C[1] = (a[1][3] - C[0] * a[1][0] - C[2] * a[1][2]) / a[1][1];
			C[2] = (a[2][3] - C[0] * a[2][0] - C[1] * a[2][1]) / a[2][2];
			
			if ( ((C[1]-er0)/C[1])<er)
			{
				n=0;
			}
			er0=C[1];
	}


			FILE *fp1;
			fp1 = fopen("results.dat","w+");
			fprintf(fp1,"C[1] = %8.4f \n",C[0]);
			fprintf(fp1,"C[2] = %8.4f \n",C[1]);
			fprintf(fp1,"C[3] = %8.4f \n",C[2]);
}

[Brandybuck]

This is my full code now and i have no idea why its not running. I'm not getting any errors. I think its doing an infinite loop.

#include<iostream>
#include<cmath>
#include<cstdio>
#include<stdio.h>
#include<fstream>

using namespace std;

void GaussSeidel(double a[3][4])
{
	double C[3], er, er0;
	C[0] = a[0][3] / a[0][0];
	C[1] = a[1][3] / a[1][1];
	C[2] = a[2][3] / a[2][2];
	er=5e-20;
	er0=0;
	int n;
	while (n)
	{

			C[0] = (a[0][3] - C[1] * a[0][1] - C[2] * a[0][2]) / a[0][0];
			C[1] = (a[1][3] - C[0] * a[1][0] - C[2] * a[1][2]) / a[1][1];
			C[2] = (a[2][3] - C[0] * a[2][0] - C[1] * a[2][1]) / a[2][2];
			
			if ( ((C[1]-er0)/C[1])<er)
		{
				n=0;
		}
			er0=C[1];
	}
}
void GaussSeidel();
int main()
{
	int i,j;
	double a[3][4], C[3];
	FILE *fu;
	fu=fopen("datafile.dat","r+");

	if (fu == NULL)
	{
		cout << "file doesn't open\n";
	}
		for (i=0;i<3;i++)
		for (j=0;j<4;j++)
	{
		fscanf(fu," %1f ",&a[i][j]);
	}
GaussSeidel(a);
FILE *fp;
fp = fopen("results.dat","w+");
fscanf(fp," %1f ", &C[3]);
fprintf(fp,"C[1] = %8.4f \n",C[0]);
fprintf(fp,"C[2] = %8.4f \n",C[1]);
fprintf(fp,"C[3] = %8.4f \n",C[2]);
fclose (fu);
return 0;
}

[Brandybuck]

btw this is due at midnight please help

[ar569]

Dr. Lang got us all worked up now hasnt he?

[Brandybuck]

lol did you finish?

[Brandybuck]

are you Dr. Lang?

[ar569]

nah, im here for resources

[Brandybuck]

are you in CEI?

[ar569]

lmao no, who you doe?