```/* nag_lapacklin_zpbsv (f07hnc) Example Program.
*
* Copyright 2020 Numerical Algorithms Group.
*
* Mark 27.1, 2020.
*/

#include <nag.h>
#include <stdio.h>

int main(void) {
/* Scalars */
Integer exit_status = 0, i, j, kd, n, nrhs, pdab, pdb;

/* Arrays */
Complex *ab = 0, *b = 0;
char nag_enum_arg[40];

/* Nag Types */
NagError fail;
Nag_UploType uplo;
Nag_OrderType order;

#ifdef NAG_COLUMN_MAJOR
#define AB_UPPER(I, J) ab[(J - 1) * pdab + kd + I - J]
#define AB_LOWER(I, J) ab[(J - 1) * pdab + I - J]
#define B(I, J) b[(J - 1) * pdb + I - 1]
order = Nag_ColMajor;
#else
#define AB_UPPER(I, J) ab[(I - 1) * pdab + J - I]
#define AB_LOWER(I, J) ab[(I - 1) * pdab + kd + J - I]
#define B(I, J) b[(I - 1) * pdb + J - 1]
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_lapacklin_zpbsv (f07hnc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &kd, &nrhs);
if (n < 0 || kd < 0 || nrhs < 0) {
printf("Invalid n, kd or nrhs\n");
exit_status = 1;
goto END;
}
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);

/* Allocate memory */
if (!(ab = NAG_ALLOC((kd + 1) * n, Complex)) ||
!(b = NAG_ALLOC(n * nrhs, Complex))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
pdab = kd + 1;
#ifdef NAG_COLUMN_MAJOR
pdb = n;
#else
pdb = nrhs;
#endif

/* Read the upper or lower triangular part of the band matrix A
* from data file
*/

if (uplo == Nag_Upper)
for (i = 1; i <= n; ++i)
for (j = i; j <= MIN(n, i + kd); ++j)
scanf(" ( %lf , %lf )", &AB_UPPER(i, j).re, &AB_UPPER(i, j).im);
else
for (i = 1; i <= n; ++i)
for (j = MAX(1, i - kd); j <= i; ++j)
scanf(" ( %lf , %lf )", &AB_LOWER(i, j).re, &AB_LOWER(i, j).im);
scanf("%*[^\n]");

/* Read b from data file */
for (i = 1; i <= n; ++i)
for (j = 1; j <= nrhs; ++j)
scanf(" ( %lf , %lf )", &B(i, j).re, &B(i, j).im);
scanf("%*[^\n]");

/* Solve the equations Ax = b for x using nag_lapacklin_zpbsv (f07hnc). */
nag_lapacklin_zpbsv(order, uplo, n, kd, nrhs, ab, pdab, b, pdb, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_zpbsv (f07hnc).\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("(%7.4f, %7.4f)%s", B(i, j).re, B(i, j).im,
j % 4 == 0 ? "\n" : " ");
printf("\n");
}
printf("\n");

/* Print details of factorization using
* nag_file_print_matrix_complex_band_comp (x04dfc).
*/
fflush(stdout);
if (uplo == Nag_Upper)
nag_file_print_matrix_complex_band_comp(
order, n, n, 0, kd, ab, pdab, Nag_BracketForm, "%7.4f",
"Cholesky factor U", Nag_IntegerLabels, 0, Nag_IntegerLabels, 0, 80, 0,
0, &fail);
else
nag_file_print_matrix_complex_band_comp(
order, n, n, kd, 0, ab, pdab, Nag_BracketForm, "%7.4f",
"Cholesky factor L", Nag_IntegerLabels, 0, Nag_IntegerLabels, 0, 80, 0,
0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_complex_band_comp (x04dfc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
END:
NAG_FREE(ab);
NAG_FREE(b);

return exit_status;
}

#undef AB_UPPER
#undef AB_LOWER
#undef B
```