/* nag_zgtcon (f07cuc) Example Program. * * Copyright 2004 Numerical Algorithms Group. * * Mark 23, 2011 * */ #include #include #include #include #include #include int main(void) { /* Scalars */ double anorm, rcond; Integer exit_status = 0, i, n; /* Arrays */ Complex *d = 0, *dl = 0, *du = 0, *du2 = 0; Integer *ipiv = 0; /* Nag Types */ NagError fail; #define CABS(dl) sqrt(dl.re * dl.re + dl.im * dl.im) INIT_FAIL(fail); printf("nag_zgtcon (f07cuc) 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 = -2; goto END; } /* Allocate memory */ if (!(d = NAG_ALLOC(n, Complex)) || !(dl = NAG_ALLOC(n-1, Complex)) || !(du = NAG_ALLOC(n-1, Complex)) || !(du2 = NAG_ALLOC(n-2, Complex)) || !(ipiv = NAG_ALLOC(n, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read the tridiagonal matrix A from data file */ for (i = 0; i < n - 1; ++i) scanf(" ( %lf , %lf )", &du[i].re, &du[i].im); scanf("%*[^\n]"); for (i = 0; i < n; ++i) scanf(" ( %lf , %lf )", &d[i].re, &d[i].im); scanf("%*[^\n]"); for (i = 0; i < n - 1; ++i) scanf(" ( %lf , %lf )", &dl[i].re, &dl[i].im); scanf("%*[^\n]"); /* Compute the 1-norm of A */ if (n == 1) { anorm = CABS(d[0]); } else { anorm = MAX(CABS(d[0])+CABS(dl[0]), CABS(d[n-1])+CABS(du[n-2])); for (i = 1; i < n-1; ++i) anorm = MAX(anorm, CABS(d[i])+CABS(dl[i])+CABS(du[i-1])); } /* nag_zgttrf (f07crc) * LU factorization of complex tridiagonal matrix A */ nag_zgttrf(n, dl, d, du, du2, ipiv, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_zgttrf (f07crc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Estimate the condition number of A using * nag_zgtcon (f07cuc). * Estimates the reciprocal of the condition number of a LU factorized * complex tridiagonal matrix. */ nag_zgtcon(Nag_OneNorm, n, dl, d, du, du2, ipiv, anorm, &rcond, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_zgtcon (f07cuc).\n%s\n", fail.message); exit_status = 2; 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: NAG_FREE(d); NAG_FREE(dl); NAG_FREE(du); NAG_FREE(du2); NAG_FREE(ipiv); return exit_status; }