/* nag_lapacklin_dpotrf (f07fdc) Example Program.
*
* Copyright 2024 Numerical Algorithms Group.
*
* Mark 30.1, 2024.
*/
#include <nag.h>
#include <stdio.h>
int main(void) {
/* Scalars */
Integer i, j, n, pda;
Integer exit_status = 0;
Nag_UploType uplo;
Nag_MatrixType matrix;
NagError fail;
Nag_OrderType order;
/* Arrays */
char nag_enum_arg[40];
double *a = 0;
#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
order = Nag_RowMajor;
#endif
INIT_FAIL(fail);
printf("nag_lapacklin_dpotrf (f07fdc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
pda = n;
#else
pda = n;
#endif
/* Allocate memory */
if (!(a = NAG_ALLOC(n * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Read A from data file */
scanf(" %39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);
if (uplo == Nag_Upper) {
matrix = Nag_UpperMatrix;
for (i = 1; i <= n; ++i) {
for (j = i; j <= n; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
} else {
matrix = Nag_LowerMatrix;
for (i = 1; i <= n; ++i) {
for (j = 1; j <= i; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
}
/* Factorize A */
/* nag_lapacklin_dpotrf (f07fdc).
* Cholesky factorization of real symmetric
* positive-definite matrix
*/
nag_lapacklin_dpotrf(order, uplo, n, a, pda, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_dpotrf (f07fdc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print factor */
/* nag_file_print_matrix_real_gen (x04cac).
* Print real general matrix (easy-to-use)
*/
fflush(stdout);
nag_file_print_matrix_real_gen(order, matrix, Nag_NonUnitDiag, n, n, a, pda,
"Factor", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
END:
NAG_FREE(a);
return exit_status;
}