/*
*-----------------------------------------------------------------------------
* funct: mat_lsolve
* desct: solve linear equations
* given: a = square matrix A
* b = column matrix B
* retrn: column matrix X (of AX = B)
*-----------------------------------------------------------------------------
*/
MATRIX mat_lsolve(MATRIX a,MATRIX b,MATRIX X)
{
MATRIX A, B, P;
int n;
n = MatCol(a);
if ( ( A = mat_creat(n, n, UNDEFINED) ) == NULL )
return (NULL);
if ( ( B = mat_creat(n, 1, UNDEFINED) ) == NULL )
return (NULL);
mat_copy(a,A);
mat_copy(b,B);
if ( ( P = mat_creat(n, 1, UNDEFINED) ) == NULL )
return (NULL);
// if dimensions of C is wrong
if ( MatRow(X) != n || MatCol(X) != 1 ) {
printf("mat_lsolve error: incompatible output matrix size\n");
_exit(-1);
// if dimensions of C is correct
} else {
mat_lu( A, P );
mat_backsubs1( A, B, X, P, 0 );
}
mat_free(A);
mat_free(B);
mat_free(P);
return(X);
}
/*
*-----------------------------------------------------------------------------
* funct: mat_inv
* desct: find inverse of a matrix
* given: a = square matrix a
* retrn: square matrix Inverse(A)
* NULL = fails, singular matrix, or malloc() fails
* 1 = success
*-----------------------------------------------------------------------------
*/
MATRIX mat_inv(MATRIX a, MATRIX C)
{
MATRIX A, B, P;
int i, n;
n = MatCol(a);
if ( ( A = mat_creat( n, n, UNDEFINED ) ) == NULL )
return (NULL);
mat_copy(a,A);
if ( ( B = mat_creat( n, 1, UNDEFINED ) ) == NULL )
return (NULL);
if ( ( P = mat_creat( n, 1, UNDEFINED ) ) == NULL )
return (NULL);
// if dimensions of C is wrong
if ( MatRow(a) != MatRow(C) || MatCol(a) != MatCol(C) ) {
printf("mat_inv error: incompatible output matrix size\n");
_exit(-1);
// if dimensions of C is correct
} else {
/*
* - LU-decomposition -
* also check for singular matrix
*/
if (mat_lu(A, P) == -1) {
mat_free(A);
mat_free(B);
mat_free(C);
mat_free(P);
printf("mat_inv error: failed to invert\n");
return (NULL);
}
for (i=0; i<n; i++) {
mat_fill(B, ZERO_MATRIX);
B[i][0] = 1.0;
mat_backsubs1( A, B, C, P, i );
}
}
mat_free(A);
mat_free(B);
mat_free(P);
if (C==NULL) {
printf("mat_inv error: failed to invert\n");
return(NULL);
} else {
return (C);
}
}
/*
*-----------------------------------------------------------------------------
* funct: mat_inv
* desct: find inverse of a matrix
* given: a = square matrix a, and C, return for inv(a)
* retrn: square matrix Inverse(A), C
* NULL = fails, singular matrix
*-----------------------------------------------------------------------------
*/
MATRIX mat_inv( MATRIX a , MATRIX C)
{
MATRIX A, B, P;
int i, n;
#ifdef CONFORM_CHECK
if(MatCol(a)!=MatCol(C))
{
error("\nUnconformable matrices in routine mat_inv(): Col(A)!=Col(B)\n");
}
if(MatRow(a)!=MatRow(C))
{
error("\nUnconformable matrices in routine mat_inv(): Row(A)!=Row(B)\n");
}
#endif
n = MatCol(a);
A = mat_creat(MatRow(a), MatCol(a), UNDEFINED);
A = mat_copy(a, A);
B = mat_creat( n, 1, UNDEFINED );
P = mat_creat( n, 1, UNDEFINED );
/*
* - LU-decomposition -
* also check for singular matrix
*/
if (mat_lu(A, P) == -1)
{
mat_free(A);
mat_free(B);
mat_free(P);
return (NULL);
}
else
{
/* Bug??? was still mat_backsubs1 even when singular??? */
for (i=0; i<n; i++)
{
mat_fill(B, ZERO_MATRIX);
B[i][0] = 1.0;
mat_backsubs1( A, B, C, P, i );
}
mat_free(A);
mat_free(B);
mat_free(P);
return (C);
}
}
