/* nag_zero_nonlin_eqns_easy (c05qbc) Example Program. * * Copyright 2013 Numerical Algorithms Group. * * Mark 24, 2013. */ #include #include #include #include #include #include #ifdef __cplusplus extern "C" { #endif static void NAG_CALL fcn(Integer n, const double x[], double fvec[], Nag_Comm *comm, Integer *iflag); #ifdef __cplusplus } #endif int main(void) { static double ruser[1] = {-1.0}; Integer exit_status = 0, i, n = 9; double *fvec = 0, *x = 0, xtol; /* Nag Types */ NagError fail; Nag_Comm comm; INIT_FAIL(fail); printf("nag_zero_nonlin_eqns_easy (c05qbc) Example Program Results\n"); /* For communication with user-supplied functions: */ comm.user = ruser; if (n > 0) { if (!(fvec = NAG_ALLOC(n, double)) || !(x = NAG_ALLOC(n, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } } else { printf("Invalid n.\n"); exit_status = 1; goto END; } /* The following starting values provide a rough solution. */ for (i = 0; i < n; i++) x[i] = -1.0; /* nag_machine_precision (x02ajc). * The machine precision */ xtol = sqrt(nag_machine_precision); /* nag_zero_nonlin_eqns_easy (c05qbc). * Solution of a system of nonlinear equations (function * values only) */ nag_zero_nonlin_eqns_easy(fcn, n, x, fvec, xtol, &comm, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_zero_nonlin_eqns_easy (c05qbc).\n%s\n", fail.message); exit_status = 1; if (fail.code != NE_TOO_MANY_FEVALS && fail.code != NE_TOO_SMALL && fail.code != NE_NO_IMPROVEMENT) goto END; } printf(fail.code == NE_NOERROR ? "Final approximate" : "Approximate"); printf(" solution\n\n"); for (i = 0; i < n; i++) printf("%12.4f%s", x[i], (i%3 == 2 || i == n-1)?"\n":" "); if (fail.code != NE_NOERROR) exit_status = 2; END: NAG_FREE(fvec); NAG_FREE(x); return exit_status; } static void NAG_CALL fcn(Integer n, const double x[], double fvec[], Nag_Comm *comm, Integer *iflag) { Integer k; if (comm->user[0] == -1.0) { printf("(User-supplied callback fcn, first invocation.)\n"); comm->user[0] = 0.0; } for (k = 0; k < n; ++k) { fvec[k] = (3.0-x[k]*2.0)*x[k]+1.0; if (k > 0) fvec[k] -= x[k-1]; if (k < n-1) fvec[k] -= x[k+1]*2.0; } /* Set iflag negative to terminate execution for any reason. */ *iflag = 0; }