/* nag_dgtsvx (f07cbc) Example Program.
*
* NAGPRODCODE Version.
*
* Copyright 2016 Numerical Algorithms Group.
*
* Mark 26, 2016.
*/
#include <stdio.h>
#include <nag.h>
#include <nagx04.h>
#include <nag_stdlib.h>
#include <nagf07.h>
int main(void)
{
/* Scalars */
double rcond;
Integer exit_status = 0, i, j, n, nrhs, pdb, pdx;
/* Arrays */
double *b = 0, *berr = 0, *d = 0, *df = 0, *dl = 0, *dlf = 0, *du = 0;
double *du2 = 0, *duf = 0, *ferr = 0, *x = 0;
Integer *ipiv = 0;
/* Nag Types */
NagError fail;
Nag_OrderType order;
#ifdef NAG_COLUMN_MAJOR
#define B(I, J) b[(J-1)*pdb + I - 1]
order = Nag_ColMajor;
#else
#define B(I, J) b[(I-1)*pdb + J - 1]
order = Nag_RowMajor;
#endif
INIT_FAIL(fail);
printf("nag_dgtsvx (f07cbc) 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 (!(b = NAG_ALLOC(n * nrhs, double)) ||
!(berr = NAG_ALLOC(nrhs, double)) ||
!(d = NAG_ALLOC(n, double)) ||
!(df = NAG_ALLOC(n, double)) ||
!(dl = NAG_ALLOC(n - 1, double)) ||
!(dlf = NAG_ALLOC(n - 1, double)) ||
!(du = NAG_ALLOC(n - 1, double)) ||
!(du2 = NAG_ALLOC(n - 2, double)) ||
!(duf = NAG_ALLOC(n - 1, double)) ||
!(ferr = NAG_ALLOC(nrhs, double)) ||
!(x = NAG_ALLOC(n * nrhs, double)) || !(ipiv = NAG_ALLOC(n, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
#ifdef NAG_COLUMN_MAJOR
pdb = n;
pdx = n;
#else
pdb = nrhs;
pdx = nrhs;
#endif
/* Read the tridiagonal matrix A from data file */
for (i = 0; i < n - 1; ++i)
scanf("%lf", &du[i]);
scanf("%*[^\n]");
for (i = 0; i < n; ++i)
scanf("%lf", &d[i]);
scanf("%*[^\n]");
for (i = 0; i < n - 1; ++i)
scanf("%lf", &dl[i]);
scanf("%*[^\n]");
/* Read the right hand matrix B */
for (i = 1; i <= n; ++i)
for (j = 1; j <= nrhs; ++j)
scanf("%lf", &B(i, j));
scanf("%*[^\n]");
/* Solve the equations AX = B using nag_dgtsvx (f07cbc). */
nag_dgtsvx(order, Nag_NotFactored, Nag_NoTrans, n, nrhs, dl, d, du, dlf, df,
duf, du2, ipiv, b, pdb, x, pdx, &rcond, ferr, berr, &fail);
if (fail.code != NE_NOERROR && fail.code != NE_SINGULAR) {
printf("Error from nag_dgtsvx (f07cbc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print solution using nag_gen_real_mat_print (x04cac). */
fflush(stdout);
nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs,
x, pdx, "Solution(s)", 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;
}
/* Print solution, error bounds and condition number */
printf("\nBackward errors (machine-dependent)\n");
for (j = 0; j < nrhs; ++j)
printf("%11.1e%s", berr[j], j % 7 == 6 ? "\n" : " ");
printf("\n\nEstimated forward error bounds (machine-dependent)\n");
for (j = 0; j < nrhs; ++j)
printf("%11.1e%s", ferr[j], j % 7 == 6 ? "\n" : " ");
printf("\n\nEstimate of reciprocal condition number\n%11.1e\n", rcond);
if (fail.code == NE_SINGULAR)
printf("Error from nag_dgtsvx (f07cbc).\n%s\n", fail.message);
END:
NAG_FREE(b);
NAG_FREE(berr);
NAG_FREE(d);
NAG_FREE(df);
NAG_FREE(dl);
NAG_FREE(dlf);
NAG_FREE(du);
NAG_FREE(du2);
NAG_FREE(duf);
NAG_FREE(ferr);
NAG_FREE(x);
NAG_FREE(ipiv);
return exit_status;
}
#undef B