Thread: Read coefficients of linear equations from file and use jacobi method

Hi,

I did a function that get inputs of equations from user but I am trying to get from a file

Code:

void getInput( int numUnKnowns, double** mat ){
    int i, j;


    printf
    (
	"\nEnter values for the specified row and column below ...\n"
	"(The last column is the value for the RHS of the equation.)\n"
    );


    for( i = 0 ; i < numUnKnowns ; i++ )
    {
	mat[i] = (double*) malloc( (numUnKnowns+1)*sizeof(double) );
	puts("");
	for( j = 0 ; j < numUnKnowns+1 ; j++ )
	{
	    printf("matrix[%d][%d] : ", i, j);
	    if( scanf("%lf", &mat[i][j]) != 1 )
	    {
		--j;
		puts("Bad entry ... try again with a 'real' number.");
	    }
	    while( getchar() != '\n' ) ; /* flush stdin ... */
	}
    }


    printf("\nThe matrix entered:\n\n");
    for( i = 0 ; i < numUnKnowns ; i++ )
    {
	for( j = 0 ; j < numUnKnowns+1 ; j++ ) printf("%+9f ", mat[i][j]);
	puts("");
    }


    printf("\nPress 'Enter' to start iteration ... ");
    getchar();
}

can anyone help me how the function read the linear equation from file. assume the file has:
6x + 2y -z = 5
-2x + 4y + z = 8
3x + y + 7z = 3

jacobi function

Code:

void jacobiCalcDisplay( int numUnKnowns, double** mat ){
    int* flag;
    int i, j, counter = 0;
    double* res;
    double* var = (double*) malloc( numUnKnowns*sizeof(double) );
    res = (double*) malloc( numUnKnowns*sizeof(double) );
    flag = (int*) malloc( numUnKnowns*sizeof(int) );


    for(i = 0 ; i < numUnKnowns ; i++ )
    var[i] = res[i] = flag[i] = 0;
    printf("The initial value of each array element was set to zero ...\n\n");


    printf( "*********************\n");
    printf( "START CALCULATING ...\n");
    printf( "*********************\n");


    do
    {
	counter++;
	/* for each iteration keep a copy of the old results ... */
	for(i = 0 ; i < numUnKnowns ; i++ )
	{
	    var[i] = res[i];
	}


	if( SHOW_ITERS ) printf("\nIteration number %d ...\n", counter);


	for(i = 0 ; i < numUnKnowns ; i++ ) /* calculation */
	{
	    res[i] = mat[i][numUnKnowns];
	    for(j = 0 ; j < numUnKnowns ; j++ )
		res[i] = res[i] - mat[i][j]*var[j] ;


	    res[i] = res[i] + mat[i][i]*var[i] ;
	    res[i] = res[i] / mat[i][i] ;
	    if( SHOW_ITERS ) printf("%c = %f\n", 'a'+i, res[i]);
	    if( fabs(res[i] - var[i]) < EPSILON ) /* stop condition */
	    flag[i]++;


	    if( counter==MAX_PRINT_ITERS) SHOW_ITERS = 0;
	}


    }while( !checkFlags( numUnKnowns, flag ) );


    printf( "\n********************************\n");
    printf( "The RESULTS of %d ITERATIONS ... \n", counter);
    printf( "********************************\n");


    /*  cross check ...*/


    for( i = 0 ; i < numUnKnowns ; i++)
	var[i] = dotProd( numUnKnowns, mat[i], res );


    showXcheck( numUnKnowns, mat, res, var );


    /* show sol'n vector (again) ... and free up all dynamic memory  */


    printf("\nSolution vector ...\n");
    for( i = 0 ; i < numUnKnowns ; i++)
    {
	printf("%c = %+f\n", 'a'+i, res[i]);
	free(mat[i]);
    }
    free( mat );
    free( flag );
    free( res );
    free( var );
}

I did a function that get inputs of equations from user but I am trying to get from a file

No, you found some code that approximates what you need, and now, because you're nothing but a scoop and poop programmer, you're looking for us to give you the code to give you exactly what you need. Pretty sad.

sorry, I did my assignment by myself
I can post all my work.
Am asking how can read from file not asking do that.

> Read coefficients of linear equations from file and use jacobi method is bad enough, and a dupe thread...

Also, you copied it all out of New thread especially for students of C and C++, don't be a ........ing liar.

Originally Posted by memcpy

Also, you copied it all out of New thread especially for students of C and C++, don't be a ........ing liar.

Please do try to contain yourself.