/* nag_dptrfs (f07jhc) Example Program. * * Copyright 2004 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include #include int main(void) { /* Scalars */ Integer exit_status = 0, i, j, n, nrhs, pdb, pdx; Nag_OrderType order; /* Arrays */ double *b = 0, *berr = 0, *d = 0, *df = 0, *e = 0, *ef = 0, *ferr = 0; double *x = 0; /* Nag Types */ NagError fail; #ifdef NAG_COLUMN_MAJOR #define B(I, J) b[(J-1)*pdb + I - 1] order = Nag_ColMajor; #else #define B(I, J) b[(I-1)*pdb + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dptrfs (f07jhc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld%ld%*[^\n]", &n, &nrhs); if (n < 0 || nrhs < 0) { printf("Invalid n or nrhs\n"); exit_status = 1; goto END; } /* Allocate memory */ if (!(b = NAG_ALLOC(n * nrhs, double)) || !(berr = NAG_ALLOC(nrhs, double)) || !(d = NAG_ALLOC(n, double)) || !(df = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n-1, double)) || !(ef = NAG_ALLOC(n-1, double)) || !(ferr = NAG_ALLOC(nrhs, double)) || !(x = NAG_ALLOC(n*nrhs, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } #ifdef NAG_COLUMN_MAJOR pdb = n; pdx = n; #else pdb = nrhs; pdx = nrhs; #endif /* Read the lower bidiagonal part of the tridiagonal matrix A from */ /* data file */ for (i = 0; i < n; ++i) scanf("%lf", &d[i]); scanf("%*[^\n]"); for (i = 0; i < n - 1; ++i) scanf("%lf", &e[i]); scanf("%*[^\n]"); /* Read the right hand matrix B */ for (i = 1; i <= n; ++i) for (j = 1; j <= nrhs; ++j) scanf("%lf", &B(i, j)); scanf("%*[^\n]"); /* Copy A into DF and EF */ for (i = 0; i < n; ++i) df[i] = d[i]; for (i = 0; i < n-1; ++i) ef[i] = e[i]; /* Copy B into X using nag_dge_copy (f16qfc). */ nag_dge_copy(order, Nag_NoTrans, n, nrhs, b, pdb, x, pdx, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dge_copy (f16qfc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Factorize the copy of the tridiagonal matrix A using * nag_dpttrf (f07jdc). */ nag_dpttrf(n, df, ef, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dpttrf (f07jdc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Solve the equations AX = B using nag_dpttrs (f07jec). */ nag_dpttrs(order, n, nrhs, df, ef, x, pdx, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dpttrs (f07jec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Improve the solution and compute error estimates * using nag_dptrfs (f07jhc). */ nag_dptrfs(order, n, nrhs, d, e, df, ef, b, pdb, x, pdx, ferr, berr, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dptrfs (f07jhc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print the solution and the forward and backward error estimates * 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; } printf("\nBackward errors (machine-dependent)\n"); for (j = 0; j < nrhs; ++j) printf("%11.1e%s", berr[j], j%7 == 6?"\n":" "); printf("\n\nEstimated forward error bounds (machine-dependent)\n"); for (j = 0; j < nrhs; ++j) printf("%11.1e%s", ferr[j], j%7 == 6?"\n":" "); END: if (b) NAG_FREE(b); if (berr) NAG_FREE(berr); if (d) NAG_FREE(d); if (df) NAG_FREE(df); if (e) NAG_FREE(e); if (ef) NAG_FREE(ef); if (ferr) NAG_FREE(ferr); if (x) NAG_FREE(x); return exit_status; } #undef B