/* nag_real_tridiag_lin_solve (f04bcc) Example Program. * * Copyright 2004 Numerical Algorithms Group. * * Mark 8, 2004. */ #include #include #include #include #include int main(void) { /* Scalars */ double errbnd, rcond; Integer exit_status, i, j, n, nrhs, pdb; /* Arrays */ double *b = 0, *d = 0, *dl = 0, *du = 0, *du2 = 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 exit_status = 0; INIT_FAIL(fail); printf( "nag_real_tridiag_lin_solve (f04bcc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%ld%ld%*[^\n] ", &n, &nrhs); if (n >= 0 && nrhs >= 0) { /* Allocate memory */ if (!(b = NAG_ALLOC(n*nrhs, double)) || !(d = NAG_ALLOC(n, double)) || !(dl = NAG_ALLOC(n-1, double)) || !(du = NAG_ALLOC(n-1, double)) || !(du2 = NAG_ALLOC(n-2, double)) || !(ipiv = NAG_ALLOC(n, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } #ifdef NAG_COLUMN_MAJOR pdb = n; #else pdb = nrhs; #endif } else { printf("%s\n", "n and/or nrhs too small"); exit_status = 1; return exit_status; } /* Read A and B from data file */ for (i = 1; i <= n-1; ++i) { scanf("%lf", &du[i-1]); } scanf("%*[^\n] "); for (i = 1; i <= n; ++i) { scanf("%lf", &d[i-1]); } scanf("%*[^\n] "); for (i = 1; i <= n-1; ++i) { scanf("%lf", &dl[i-1]); } 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 */ /* nag_real_tridiag_lin_solve (f04bcc). * Computes the solution and error-bound to a real * tridiagonal system of linear equations */ nag_real_tridiag_lin_solve(order, n, nrhs, dl, d, du, du2, ipiv, b, pdb, &rcond, &errbnd, &fail); if (fail.code == NE_NOERROR) { /* Print solution, estimate of condition number and approximate */ /* error bound */ /* nag_gen_real_mat_print (x04cac). * Print real general matrix (easy-to-use) */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, b, pdb, "Solution", 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("\n"); printf("%s\n %10.1e\n", "Estimate of condition number", 1.0/rcond); printf("\n\n"); printf("%s\n %10.1e\n\n", "Estimate of error bound for computed solutions", errbnd); } else if (fail.code == NE_RCOND) { /* Matrix A is numerically singular. Print estimate of */ /* reciprocal of condition number and solution */ printf("\n%s\n%6s%10.1e\n\n\n", "Estimate of reciprocal of condition number", "", rcond); /* nag_gen_real_mat_print (x04cac), see above. */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, b, pdb, "Solution", 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; } } else if (fail.code == NE_SINGULAR) { /* The upper triangular matrix U is exactly singular. Print */ /* details of factorization */ printf("%s\n\n", "Details of factorization"); printf("%s\n", " Second super-diagonal of U"); for (i = 1; i <= n - 2; ++i) { printf("%9.4f%s", du2[i-1], i%8 == 0 || i == n - 2?"\n":" "); } printf("\n"); printf("\n%s\n", " First super-diagonal of U"); for (i = 1; i <= n-1; ++i) { printf("%9.4f%s", du[i-1], i%8 == 0 || i == n-1?"\n":" "); } printf("\n\n"); printf("%s\n", " Main diagonal of U"); for (i = 1; i <= n; ++i) { printf("%9.4f%s", d[i-1], i%8 == 0 || i == n?"\n":" "); } printf("\n\n"); printf("%s\n", " Multipliers"); for (i = 1; i <= n-1; ++i) { printf("%9.4f%s", dl[i-1], i%8 == 0 || i == n-1?"\n":" "); } printf("\n\n"); printf("%s\n", " Vector of interchanges"); for (i = 1; i <= n; ++i) { printf("%9ld%s", ipiv[i-1], i%8 == 0 || i == n?"\n":" "); } printf("\n"); } else { printf("Error from nag_real_tridiag_lin_solve (f04bcc).\n%s\n", fail.message); exit_status = 1; goto END; } END: if (b) NAG_FREE(b); if (d) NAG_FREE(d); if (dl) NAG_FREE(dl); if (du) NAG_FREE(du); if (du2) NAG_FREE(du2); if (ipiv) NAG_FREE(ipiv); return exit_status; }