/* nag_zgbcon (f07buc) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include #include int main(void) { /* Scalars */ Integer i, ipiv_len, j, kl, ku, n, pdab; Integer exit_status=0; double anorm, rcond, sum; NagError fail; Nag_OrderType order; /* Arrays */ Complex *ab=0; Integer *ipiv=0; #ifdef NAG_COLUMN_MAJOR #define AB(I,J) ab[(J-1)*pdab + kl + ku + I - J] order = Nag_ColMajor; #else #define AB(I,J) ab[(I-1)*pdab + kl + J - I] order = Nag_RowMajor; #endif INIT_FAIL(fail); Vprintf("nag_zgbcon (f07buc) Example Program Results\n\n"); /* Skip heading in data file */ Vscanf("%*[^\n] "); Vscanf("%ld%ld%ld%*[^\n] ", &n, &kl, &ku); ipiv_len = n; pdab = 2*kl + ku + 1; /* Allocate memory */ if ( !(ab = NAG_ALLOC((2*kl+ku+1) * n, Complex)) || !(ipiv = NAG_ALLOC(ipiv_len, Integer)) ) { Vprintf("Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ for (i = 1; i <= n; ++i) { for (j = MAX(i-kl,1); j <= MIN(i+ku,n); ++j) Vscanf(" ( %lf , %lf )", &AB(i,j).re, &AB(i,j).im); } Vscanf("%*[^\n] "); /* Compute norm of A */ anorm = 0.0; for (j = 1; j <= n; ++j) { sum = 0.0; for (i = MAX(j-ku,1); i <= MIN(j+kl,n); ++i) /* nag_complex_abs (a02dbc). * Modulus of a complex number */ sum = sum + nag_complex_abs(AB(i,j)); anorm = MAX(anorm,sum); } /* Factorize A */ /* nag_zgbtrf (f07brc). * LU factorization of complex m by n band matrix */ nag_zgbtrf(order, n, n, kl, ku, ab, pdab, ipiv, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_zgbtrf (f07brc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Estimate condition number */ /* nag_zgbcon (f07buc). * Estimate condition number of complex band matrix, matrix * already factorized by nag_zgbtrf (f07brc) */ nag_zgbcon(order, Nag_OneNorm, n, kl, ku, ab, pdab, ipiv, anorm, &rcond, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_zgbcon (f07buc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print condition number */ /* nag_machine_precision (x02ajc). * The machine precision */ if (rcond > X02AJC) Vprintf("Estimate of condition number = %10.2e\n",1.0/rcond); else Vprintf("A is singular to working precision\n"); END: if (ab) NAG_FREE(ab); if (ipiv) NAG_FREE(ipiv); return exit_status; }