/* nag_dptcon (f07jgc) Example Program. * * Copyright 2004 Numerical Algorithms Group. * * Mark 23, 2011. * * UNFINISHED - replace commented out climp calls */ #include #include #include #include #include int main(void) { /* Scalars */ double anorm, rcond; Integer exit_status = 0, i, n; /* Arrays */ double *d = 0, *e = 0; /* Nag Types */ NagError fail; INIT_FAIL(fail); printf("nag_dptcon (f07jgc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld%*[^\n]", &n); if (n < 0) { printf("Invalid n\n"); exit_status = 1; goto END; } /* Allocate memory */ if (!(d = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n-1, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read the lower bidiagonal part of the tridiagonal matrix A 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]"); /* Compute the 1-norm of A */ anorm = MAX(ABS(d[0])+ABS(e[0]), ABS(e[n-2])+ABS(d[n-1])); for (i = 1; i < n-1; ++i) anorm = MAX(anorm, ABS(d[i])+ABS(e[i])+ABS(e[i-1])); /* Factorize the tridiagonal matrix A using nag_dgbsv (f07bac). */ nag_dpttrf(n, d, e, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgbsv (f07bac).\n%s\n", fail.message); exit_status = 1; goto END; } /* Estimate the condition number of A using nag_dptcon (f07jgc). */ nag_dptcon(n, d, e, anorm, &rcond, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dptcon (f07jgc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print the estimated condition number */ if (rcond >= nag_machine_precision) printf("Estimate of condition number = %11.2e\n\n", 1.0/rcond); else printf("A is singular to working precision. RCOND = %11.2e\n\n", rcond); END: if (d) NAG_FREE(d); if (e) NAG_FREE(e); return exit_status; }