Thread: Jacobi Iteration Method

Hello again, everyone. I've since moved away from my full-on matrice based solution and trying to do some manual computing now. I've done the thing myself, solved a linear equation system with 10 unknowns by hand, and found out the approximate solutions. However badly coded, the program should still give (as I've to hand in the project in a few hours) adequate results.

I cannot, however, for the love of god, get make my file-reading working. I've tried anything I can think of. It might be the lack of sleep, or whatever else.. Would anyone here be able to spot anything wrong with the file opening phase? It'd seem the error is there, as when I try to print the array I have got the file contents stored to, it just gives weird values... I'd greatly appreciate if anyone could help me out here and point out the problem.

P.S.: I'm using the algorithm mentioned here Here's the code and the 2 data textfiles..

SOURCE:

Code:

#include <stdio.h>
#include <stdlib.h>

#define VAR 100
#define n 10

void Read();
void Calculeet(float temp[VAR]);

int main()
{
	
	Read();
	
	

	
	return 0;
}
	
void Read()
{
	int i = 0;
	float temp[VAR];
	
	
	FILE *pData;
	pData = fopen("data2.txt", "r");
	
	if (pData == NULL)
	{
		fprintf(stderr, "Dosya açılamadı\n");
		exit(1);
	}
	
	while (!feof(pData))
	{
		fscanf (pData, "%f ", &temp[i]);
		i++;
			//for (i = 0;i < 30;i++)
	printf("%f\n", temp[i]);
	}
	
	fclose (pData);
	
	Calculeet(temp);

}

void Calculeet(float temp[VAR])
{


	float A[n],B[n],C[n],D[n],E[n],F[n],G[n],H[n],I[n],J[n],Z[n],tempa[1000],tempb[1000],tempc[1000]
	,tempd[1000],tempe[1000],tempf[1000],tempg[1000],temph[1000],tempi[1000],tempj[1000];
	int i = 0;
	
	
	
	FILE *pDataB;
	pDataB = fopen("DataB.txt", "r");
	
	
	if (pDataB == NULL)
	{
		fprintf(stderr, "Dosya açılamadı\n");
		exit(1);
	}
	
	while (!feof(pDataB))
	{
		fscanf (pDataB, "%f", &Z[i]);
		i++;
		
		printf("%f\n", Z[i]);
	}
	
	fclose (pDataB);
	
	
	printf ("%f\n%f\n", temp[0], temp[1]);
	
	i = 0;
	

	
	do
	{
	
	if (abs(i % 10) == 0)
		A[i%10] = temp[i];
	else if (abs(i % 10) == 1)
		B[i%10] = temp[i];
	else if (abs(i % 10) == 2)
		C[i%10] = temp[i];
	else if (abs(i % 10) == 3)
		D[i%10] = temp[i];	
	else if (abs(i % 10) == 4)
		E[i%10] = temp[i];
	else if (abs(i % 10) == 5)
		F[i%10] = temp[i];
	else if (abs(i % 10) == 6)
		G[i%10] = temp[i];
	else if (abs(i % 10) == 7)
		H[i%10] = temp[i];
	else if (abs(i % 10) == 8)
		I[i%10] = temp[i];
	else if (abs(i % 10) == 9)
	{
		J[i%10] = temp[i];
	}
	
	i++;
		
		
	} while (i < 100);
	printf("%f\n", A[0]);
	printf("%f\n", A[1]);
	printf("%f\n", A[2]);
	printf("%f\n", A[3]);
	printf("%f\n", A[4]);
	printf("%f\n", A[5]);
	printf("%f\n", A[6]);
	printf("%f\n", A[7]);
	printf("%f\n", A[8]);
	
	
		
	while (i <= 50)
	{
	tempa[i+1] = (Z[0]/A[0]) - (B[0]*tempb[i]/A[0]) - (C[0]*tempc[i]/A[0]) - (D[0]*tempd[i]/A[0]) - (E[0]*tempe[i]/A[0]) - (F[0]*tempf[i]/A[0])
	- (G[0]*tempg[i]/A[0]) - (H[0]*temph[i]/A[0]) - (I[0]*tempi[i]/A[0]) - (J[0]*tempj[i]/A[0]);
	tempb[i+1] = (Z[1]/B[1]) - (A[1]*tempa[i]/B[1]) - (C[1]*tempc[i]/B[1]) - (D[1]*tempd[i]/B[1]) - (E[1]*tempe[i]/B[1]) - (F[1]*tempf[i]/B[1]) 
	- (G[1]*tempg[i]/B[1]) - (H[1]*temph[i]/B[1]) - (I[1]*tempi[i]/B[1]) - (J[1]*tempj[i]/B[1]);
	tempc[i+1] = (Z[2]/C[2]) - (B[2]*tempb[i]/C[2]) - (A[2]*tempa[i]/C[2]) - (D[2]*tempd[i]/C[2]) - (E[2]*tempe[i]/C[2]) - (F[2]*tempf[i]/C[2]) 
	- (G[2]*tempg[i]/C[2]) - (H[2]*temph[i]/C[2]) - (I[2]*tempi[i]/C[2]) - (J[2]*tempj[i]/C[2]);
	tempd[i+1] = (Z[3]/D[3]) - (B[3]*tempb[i]/D[3]) - (A[3]*tempa[i]/D[3]) - (C[3]*tempc[i]/D[3]) - (E[3]*tempe[i]/D[3]) - (F[3]*tempf[i]/D[3]) 
	- (G[3]*tempg[i]/D[3]) - (H[3]*temph[i]/D[3]) - (I[3]*tempi[i]/D[3]) - (J[3]*tempj[i]/D[3]);
	tempe[i+1] = (Z[4]/E[4]) - (B[4]*tempb[i]/E[4]) - (A[4]*tempa[i]/E[4]) - (C[4]*tempc[i]/E[4]) - (D[4]*tempd[i]/E[4]) - (F[4]*tempf[i]/E[4]) 
	- (G[4]*tempg[i]/E[4]) - (H[4]*temph[i]/E[4]) - (I[4]*tempi[i]/E[4]) - (J[4]*tempj[i]/E[4]);
	tempf[i+1] = (Z[5]/F[5]) - (B[5]*tempb[i]/F[5]) - (A[5]*tempa[i]/F[5]) - (C[5]*tempc[i]/F[5]) - (D[5]*tempd[i]/F[5]) - (E[5]*tempe[i]/F[5]) 
	- (G[5]*tempg[i]/F[5]) - (H[5]*temph[i]/F[5]) - (I[5]*tempi[i]/F[5]) - (J[5]*tempj[i]/F[5]);
	tempg[i+1] = (Z[6]/G[6]) - (B[6]*tempb[i]/G[6]) - (A[6]*tempa[i]/G[6]) - (C[6]*tempc[i]/G[6]) - (D[6]*tempd[i]/G[6]) - (E[6]*tempe[i]/G[6]) 
	- (F[6]*tempf[i]/G[6]) - (H[6]*temph[i]/G[6]) - (I[6]*tempi[i]/G[6]) - (J[6]*tempj[i]/G[6]);
	temph[i+1] = (Z[7]/H[7]) - (B[7]*tempb[i]/H[7]) - (A[7]*tempa[i]/H[7]) - (C[7]*tempc[i]/H[7]) - (D[7]*tempd[i]/H[7]) - (E[7]*tempe[i]/H[7]) 
	- (F[7]*tempf[i]/H[7]) - (G[7]*tempg[i]/H[7]) - (I[7]*tempi[i]/H[7]) - (J[7]*tempj[i]/H[7]);
	tempi[i+1] = (Z[8]/I[8]) - (B[8]*tempb[i]/I[8]) - (A[8]*tempa[i]/I[8]) - (C[8]*tempc[i]/I[8]) - (D[8]*tempd[i]/I[8]) - (E[8]*tempe[i]/I[8]) 
	- (F[8]*tempf[i]/I[8]) - (G[8]*tempg[i]/I[8]) - (H[8]*temph[i]/I[8]) - (J[8]*tempj[i]/I[8]);
	tempj[i+1] = (Z[9]/J[9]) - (B[9]*tempb[i]/J[9]) - (A[9]*tempa[i]/J[9]) - (C[9]*tempc[i]/J[9]) - (D[9]*tempd[i]/J[9]) - (E[9]*tempe[i]/J[9]) 
	- (F[9]*tempf[i]/J[9]) - (G[9]*tempg[i]/J[9]) - (H[9]*temph[i]/J[9]) - (I[9]*tempi[i]/J[9]);
	
	printf("%.5f %.5f %.5f %.5f %.5f %.5f\n\n", tempa[i], tempb[i], tempc[i], tempd[i], tempe[i], tempf[i]);
	printf("%.5f %.5f %.5f %.5f\n\n", tempg[i], temph[i], tempi[i], tempj[i]);
	i++;
	}
}

data2.TXT

Code:

-30 -11 47 -8 38 -45 26 7 11 18
34 -36 43 39 13 48 40 -37 -39 -17
-29 44 -7 32 25 21 -50 -45 27 15
-23 42 -38 -33 1 -44 41 25 -36 -32
-3 -39 -23 -20 -10 36 -16 -45 -32 16
-31 -36 -41 0 -25 -23 37 24 -30 47
43 34 -44 -26 5 -14 40 -50 -22 -12
-49 -26 -38 34 35 -3 -7 6 50 -14
31 49 44 -32 16 -6 46 -27 36 -15
6 13 1 20 48 42 14 -3 -17 9

DataB.txt:

Code:

10
5
6
-30
40
-29
-5
0
10
7

I dunno what you mean by "weird values" but this won't make it past the first newline, if there is one:

Code:

fscanf (pData, "%f ", &temp[i]);

You should examine the return value of fscanf -- in fact, you should probably make use of it for error handling.

Code:

	{

	if (abs(i % 10) == 0)
		A[i%10] = temp[i];
	else if (abs(i % 10) == 1)
		B[i%10] = temp[i];
	else if (abs(i % 10) == 2)
		C[i%10] = temp[i];
	else if (abs(i % 10) == 3)
		D[i%10] = temp[i];	
	else if (abs(i % 10) == 4)
		E[i%10] = temp[i];
	else if (abs(i % 10) == 5)
		F[i%10] = temp[i];
	else if (abs(i % 10) == 6)
		G[i%10] = temp[i];
	else if (abs(i % 10) == 7)
		H[i%10] = temp[i];
	else if (abs(i % 10) == 8)
		I[i%10] = temp[i];
	else if (abs(i % 10) == 9)
	{
		J[i%10] = temp[i];
	}

1) Surely this is what switch statements were invented for.

2) Don't control loops with feof()
Cprogramming.com FAQ > Why it's bad to use feof() to control a loop

Sounds good. Keep working on it and aim to finish well before the deadline. There is no better feeling than having a good time and going to bed at your convenience the night before the deadline when slackers are chugging red bull and coffee. Post here any specific questions you have.

This program screams: Use two dimensional arrays!

Originally Posted by iMalc

This program screams: Use two dimensional arrays!

Definitely, also use Fortran instead.

Also, sounds like the OP is doing a homework assignment. If not, Jacobi/Gauss-Seidel are poor choices to solve matrices and will only converge for well-conditioned matrices. Successive over-relaxation (SOR) is like Gauss-Seidel but exhibits better convergence. There are a lot of options, but Jacobi/Gauss-Seidel are probably the last ones you want to use.