/* nag_dptsv (f07jac) Example Program. * * Copyright 2004 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include int main(void) { /* Scalars */ Integer exit_status = 0, i, j, n, nrhs, pdb; Nag_OrderType order; /* Arrays */ double *b = 0, *d = 0, *e = 0; /* Nag Types */ NagError fail; #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_dptsv (f07jac) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld%ld%*[^\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)) || !(d = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n-1, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } #ifdef NAG_COLUMN_MAJOR pdb = n; #else pdb = nrhs; #endif /* Read the lower bidiagonal part of the tridiagonal matrix A and the * right hand side b from data file. */ for (i = 0; i < n; ++i) scanf("%lf", &d[i]); scanf("%*[^\n]"); for (i = 0; i < n - 1; ++i) scanf("%lf", &e[i]); scanf("%*[^\n]"); 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_dptsv (f07jac). */ nag_dptsv(order, n, nrhs, d, e, b, pdb, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dptsv (f07jac).\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 */ printf("\nDiagonal elements of the diagonal matrix D\n"); for (i = 0; i < n; ++i) printf("%11.4f%s", d[i], i%7 == 6?"\n":" "); printf("\n\nSub-diagonal elements of the Cholesky factor L\n"); for (i = 0; i < n-1; ++i) printf("%11.4f%s", e[i], i%7 == 6?"\n":" "); printf("\n"); END: NAG_FREE(b); NAG_FREE(d); NAG_FREE(e); return exit_status; }