/* nag_dgecon (f07agc) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. * Mark 7b revised, 2004. */ #include #include #include #include #include #include #include int main(void) { /* Scalars */ double anorm, rcond; Integer exit_status = 0; Integer i, ipiv_len, j, n, pda; NagError fail; Nag_OrderType order; /* Arrays */ double *a = 0; Integer *ipiv = 0; #ifdef NAG_COLUMN_MAJOR #define A(I, J) a[(J-1)*pda + I - 1] order = Nag_ColMajor; #else #define A(I, J) a[(I-1)*pda + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dgecon (f07agc) Example Program Results\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%ld%*[^\n] ", &n); pda = n; ipiv_len = n; /* Allocate memory */ if (!(a = NAG_ALLOC(n * n, double)) || !(ipiv = NAG_ALLOC(ipiv_len, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ for (i = 1; i <= n; ++i) { for (j = 1; j <= n; ++j) scanf("%lf", &A(i, j)); } scanf("%*[^\n] "); /* Compute norm of A */ /* nag_dge_norm (f16rac). * 1-norm, infinity-norm, Frobenius norm, largest absolute * element, real general matrix */ nag_dge_norm(order, Nag_OneNorm, n, n, a, pda, &anorm, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dge_norm (f16rac).\n%s\n", fail.message); exit_status = 1; goto END; } /* Factorize A */ /* nag_dgetrf (f07adc). * LU factorization of real m by n matrix */ nag_dgetrf(order, n, n, a, pda, ipiv, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgetrf (f07adc).\n%s\n", fail.message); exit_status = 1; goto END; } printf("\n"); /* Estimate condition number */ /* nag_dgecon (f07agc). * Estimate condition number of real matrix, matrix already * factorized by nag_dgetrf (f07adc) */ nag_dgecon(order, Nag_OneNorm, n, a, pda, anorm, &rcond, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgecon (f07agc).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_machine_precision (x02ajc). * The machine precision */ if (rcond >= nag_machine_precision) { printf("Estimate of condition number =%11.2e\n", 1.0/rcond); } else printf("A is singular to working precision\n"); END: NAG_FREE(a); NAG_FREE(ipiv); return exit_status; }