/* nag_dgtrfs (f07chc) 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; /* Arrays */ double *b = 0, *berr = 0, *d = 0, *df = 0, *dl = 0, *dlf = 0, *du = 0; double *du2 = 0, *duf = 0, *ferr = 0, *x = 0; Integer *ipiv = 0; /* Nag Types */ NagError fail; Nag_OrderType order; #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_dgtrfs (f07chc) 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)) || !(dl = NAG_ALLOC(n-1, double)) || !(dlf = NAG_ALLOC(n-1, double)) || !(du = NAG_ALLOC(n-1, double)) || !(du2 = NAG_ALLOC(n-2, double)) || !(duf = NAG_ALLOC(n-1, double)) || !(ferr = NAG_ALLOC(nrhs, double)) || !(x = NAG_ALLOC(n*nrhs, double)) || !(ipiv = NAG_ALLOC(n, Integer))) { 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 tridiagonal matrix A from data file */ for (i = 0; i < n - 1; ++i) scanf("%lf", &du[i]); scanf("%*[^\n]"); for (i = 0; i < n; ++i) scanf("%lf", &d[i]); scanf("%*[^\n]"); for (i = 0; i < n - 1; ++i) scanf("%lf", &dl[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 arrays duf, df and dlf. */ for (i = 0; i < n-1; ++i) { duf[i] = du[i], df[i] = d[i], dlf[i] = dl[i]; } df[n-1] = d[n-1]; /* 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_dgttrf (f07cdc). */ nag_dgttrf(n, dlf, df, duf, du2, ipiv, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgttrf (f07cdc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Solve the equations AX = B using nag_dgttrs (f07cec). */ nag_dgttrs(order, Nag_NoTrans, n, nrhs, dlf, df, duf, du2, ipiv, x, pdx, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgttrs (f07cec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Improve the solution and compute error estimates using * nag_dgtrfs (f07chc). */ nag_dgtrfs(order, Nag_NoTrans, n, nrhs, dl, d, du, dlf, df, duf, du2, ipiv, b, pdb, x, pdx, ferr, berr, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgtrfs (f07chc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print the 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 the forward and backward error estimates */ 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":" "); printf("\n"); END: NAG_FREE(b); NAG_FREE(berr); NAG_FREE(d); NAG_FREE(df); NAG_FREE(dl); NAG_FREE(dlf); NAG_FREE(du); NAG_FREE(du2); NAG_FREE(duf); NAG_FREE(ferr); NAG_FREE(x); NAG_FREE(ipiv); return exit_status; } #undef B