/* nag_dgbsvx (f07bbc) Example Program. * * Copyright 2011 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include int main(void) { /* Scalars */ double growth_factor, rcond; Integer exit_status = 0, i, j, kl, ku, n, nrhs, pdab, pdafb, pdb, pdx; /* Arrays */ double *ab = 0, *afb = 0, *b = 0, *berr = 0, *c = 0; double *ferr = 0, *r = 0, *x = 0; Integer *ipiv = 0; /* Nag Types */ NagError fail; Nag_OrderType order; Nag_EquilibrationType equed; #ifdef NAG_COLUMN_MAJOR #define AB(I, J) ab[(J-1)*pdab + ku + I - J] #define B(I, J) b[(J-1)*pdb + I - 1] order = Nag_ColMajor; #else #define AB(I, J) ab[(I-1)*pdab + kl + J - I] #define B(I, J) b[(I-1)*pdb + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dgbsvx (f07bbc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%ld%ld%ld%ld%*[^\n]", &n, &nrhs, &kl, &ku); if (n < 0 || kl < 0 || ku < 0 || nrhs < 0) { printf("Invalid n, kl, ku or nrhs\n"); exit_status = 1; goto END; } pdab = kl+ku+1; pdafb = 2*kl+ku+1; #ifdef NAG_COLUMN_MAJOR pdx = n; pdb = n; #else pdx = nrhs; pdb = nrhs; #endif /* Allocate memory */ if (!(ab = NAG_ALLOC(pdab * n, double)) || !(afb = NAG_ALLOC(pdafb * n, double)) || !(b = NAG_ALLOC(n*nrhs, double)) || !(berr = NAG_ALLOC(nrhs, double)) || !(c = NAG_ALLOC(n, double)) || !(ferr = NAG_ALLOC(nrhs, double)) || !(r = NAG_ALLOC(n, double)) || !(x = NAG_ALLOC(n*nrhs, double)) || !(ipiv = NAG_ALLOC(n, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read the band matrix A and B from data file */ for (i = 1; i <= n; ++i) for (j = MAX(i - kl, 1); j <= MIN(i + ku, n); ++j) scanf("%lf", &AB(i, j)); scanf("%*[^\n]"); for (i = 1; i <= n; ++i) for (j = 1; j <= nrhs; ++j) scanf("%lf", &B(i, j)); scanf("%*[^\n]"); /* Solve the equations Ax = B for x using nag_dgbsvx (f07bbc). */ nag_dgbsvx(order, Nag_EquilibrateAndFactor, Nag_NoTrans, n, kl, ku, nrhs, ab, pdab, afb, pdafb, ipiv, &equed, r, c, b, pdb, x, pdx, &rcond, ferr, berr, &growth_factor, &fail); if (fail.code != NE_NOERROR && fail.code != NE_SINGULAR) { printf("Error from nag_dgbsvx (f07bbc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print solution using nag_gen_real_mat_print (x04cac). */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, x, pdx, "Solution(s)", 0, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print error bounds, condition number, the form of equilibration * and the pivot growth factor */ printf("\nBackward errors (machine-dependent)\n"); for (j = 1; j <= nrhs; ++j) printf("%11.1e%s", berr[j - 1], j%7 == 0?"\n":" "); printf("\n\nEstimated forward error bounds (machine-dependent)\n"); for (j = 1; j <= nrhs; ++j) printf("%11.1e%s", ferr[j - 1], j%7 == 0?"\n":" "); printf("\n\nEstimate of reciprocal condition number\n%11.1e\n\n", rcond); if (equed == Nag_NoEquilibration) printf("A has not been equilibrated\n"); else if (equed == Nag_RowEquilibration) printf("A has been row scaled as diag(R)*A\n"); else if (equed == Nag_ColumnEquilibration) printf("A has been column scaled as A*diag(C)\n"); else if (equed == Nag_RowAndColumnEquilibration) printf("A has been row and column scaled as diag(R)*A*diag(C)\n"); printf("\nEstimate of reciprocal pivot growth factor\n%11.1e\n", growth_factor); if (fail.code == NE_SINGULAR) printf("Error from nag_dgbsvx (f07bbc).\n%s\n", fail.message); END: if (ab) NAG_FREE(ab); if (afb) NAG_FREE(afb); if (b) NAG_FREE(b); if (berr) NAG_FREE(berr); if (c) NAG_FREE(c); if (ferr) NAG_FREE(ferr); if (r) NAG_FREE(r); if (x) NAG_FREE(x); if (ipiv) NAG_FREE(ipiv); return exit_status; } #undef AB #undef B