/* nag_real_band_lin_solve (f04bbc) 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, kl, ku, n, nrhs, pdab, pdb; /* Arrays */ double *ab=0, *b=0; Integer *ipiv=0; /* Nag Types */ NagError fail; Nag_OrderType order; #ifdef NAG_COLUMN_MAJOR #define AB(I,J) ab[(J-1)*pdab + kl + 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 exit_status = 0; INIT_FAIL(fail); Vprintf("nag_real_band_lin_solve (f04bbc) Example Program Results\n\n"); /* Skip heading in data file */ Vscanf("%*[^\n] "); Vscanf("%ld%ld%ld%ld%*[^\n] ", &n, &kl, &ku, &nrhs); if (n >= 0 && kl >=0 && ku >=0 && nrhs >=0) { /* Allocate memory */ if ( !(ab = NAG_ALLOC((2*kl+ku+1)*n, double)) || !(b = NAG_ALLOC(n*nrhs, double)) || !(ipiv = NAG_ALLOC(n, Integer)) ) { Vprintf("Allocation failure\n"); exit_status = -1; goto END; } pdab = 2*kl+ku+1; #ifdef NAG_COLUMN_MAJOR pdb = n; #else pdb = nrhs; #endif } else { Vprintf("%s\n", "One or more of nmax, kl, ku or nrhs is" " too small"); exit_status = 1; return exit_status; } /* Read A and B from data file */ for (i = 1; i <= n; ++i) { for (j = MAX(i - kl,1); j <= MIN(i + ku,n); ++j) { Vscanf("%lf", &AB(i,j)); } } Vscanf("%*[^\n] "); for (i = 1; i <= n; ++i) { for (j = 1; j <= nrhs; ++j) { Vscanf("%lf", &B(i,j)); } } Vscanf("%*[^\n] "); /* Solve the equations AX = B for X */ /* nag_real_band_lin_solve (f04bbc). * Computes the solution and error-bound to a real banded * system of linear equations */ nag_real_band_lin_solve(order, n, kl, ku, nrhs, ab, pdab, 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) */ nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, b, pdb, "Solution", 0, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; goto END; } Vprintf("\n%s\n%6s%9.1e\n\n\n", "Estimate of condition number", "", 1.0/rcond); Vprintf("%s\n%6s%9.1e\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 */ Vprintf("\n"); Vprintf("%s\n%6s%9.1e\n\n\n", "Estimate of reciprocal of condition number", "", rcond); /* nag_gen_real_mat_print (x04cac), see above. */ nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, b, pdb, "Solution", 0, &fail); if (fail.code != NE_NOERROR) { Vprintf("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 */ Vprintf("\n"); /* nag_band_real_mat_print (x04cec). * Print real packed banded matrix (easy-to-use) */ nag_band_real_mat_print(order, n, n, kl, kl+ku, ab, pdab, "Details of factorization", 0, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_band_real_mat_print (x04cec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print pivot indices */ Vprintf("\n%s\n", "Pivot indices"); for (i = 1; i <= n; ++i) { Vprintf("%11ld%s", ipiv[i - 1], i%7 == 0 || i == n ?"\n":" "); } Vprintf("\n"); } END: if (ab) NAG_FREE(ab); if (b) NAG_FREE(b); if (ipiv) NAG_FREE(ipiv); return exit_status; }