/* nag_dposv (f07fac) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.1, 2017.
*/
#include <stdio.h>
#include <nag.h>
#include <nagx04.h>
#include <nag_stdlib.h>
#include <nagf07.h>
int main(void)
{
/* Scalars */
Integer exit_status = 0, i, j, n, nrhs, pda, pdb;
/* Arrays */
double *a = 0, *b = 0;
/* Nag Types */
NagError fail;
Nag_OrderType order;
#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J-1)*pda + I - 1]
#define B(I, J) b[(J-1)*pdb + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I-1)*pda + J - 1]
#define B(I, J) b[(I-1)*pdb + J - 1]
order = Nag_RowMajor;
#endif
INIT_FAIL(fail);
printf("nag_dposv (f07fac) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &nrhs);
if (n < 0 || nrhs < 0) {
printf("Invalid n or nrhs\n");
exit_status = 1;
goto END;
}
/* Allocate memory */
if (!(a = NAG_ALLOC(n * n, double)) || !(b = NAG_ALLOC(n * nrhs, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
pda = n;
#ifdef NAG_COLUMN_MAJOR
pdb = n;
#else
pdb = nrhs;
#endif
/* Read the upper triangular part of A from data file */
for (i = 1; i <= n; ++i)
for (j = i; j <= n; ++j)
scanf("%lf", &A(i, j));
scanf("%*[^\n]");
/* Read b from data file */
for (i = 1; i <= n; ++i)
for (j = 1; j <= nrhs; ++j)
scanf("%lf", &B(i, j));
scanf("%*[^\n]");
/* Solve the equations Ax = b for x using nag_dposv (f07fac). */
nag_dposv(order, Nag_Upper, n, nrhs, a, pda, b, pdb, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dposv (f07fac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print solution */
printf("Solution\n");
for (i = 1; i <= n; ++i) {
for (j = 1; j <= nrhs; ++j)
printf("%11.4f%s", B(i, j), j % 7 == 0 ? "\n" : " ");
printf("\n");
}
/* Print details of factorization using nag_gen_real_mat_print (x04cac). */
printf("\n");
fflush(stdout);
nag_gen_real_mat_print(order, Nag_UpperMatrix, Nag_NonUnitDiag, n, n, a,
pda, "Cholesky factor U", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
END:
NAG_FREE(a);
NAG_FREE(b);
return exit_status;
}
#undef A
#undef B