/* nag_dgeev (f08nac) Example Program. * * Copyright 2011 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include int main(void) { /* Scalars */ Integer i, j, n, pda, pdvr; Integer exit_status = 0; /* Arrays */ double *a = 0, *vr = 0, *wi = 0, *wr = 0; double dummy [1]; /* Nag Types */ NagError fail; Nag_OrderType order; #ifdef NAG_COLUMN_MAJOR #define A(I, J) a[(J-1)*pda + I - 1] #define VR(I, J) vr[(J)*pdvr + I] order = Nag_ColMajor; #else #define A(I, J) a[(I-1)*pda + J - 1] #define VR(I, J) vr[(I)*pdvr + J] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dgeev (f08nac) Example Program Results\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld%*[^\n]", &n); if (n < 0) { printf("Invalid n\n"); exit_status = 1; goto END; } pda = n; pdvr = n; /* Allocate memory */ if (!(a = NAG_ALLOC(n * n, double)) || !(vr = NAG_ALLOC(n * n, double)) || !(wi = NAG_ALLOC(n, double)) || !(wr = NAG_ALLOC(n, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read the matrix A from data file */ for (i = 1; i <= n; ++i) for (j = 1; j <= n; ++j) scanf("%lf", &A(i, j)); scanf("%*[^\n]"); /* Compute the eigenvalues and right eigenvectors only of A * using nag_dgeev (f08nac). */ nag_dgeev(order, Nag_NotLeftVecs, Nag_RightVecs, n, a, pda, wr, wi, dummy, 1, vr, pdvr, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgeev (f08nac).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print eigenvalues and right eigenvectors. */ for (j = 0; j < n; ++j) { printf("\nEigenvalue %3ld = ", j+1); if (wi[j] == 0.0) printf("%13.4e\n", wr[j]); else printf(" (%11.4e, %11.4e)\n", wr[j], wi[j]); printf("\nEigenvector %2ld\n", j+1); if (wi[j] == 0.0) for (i = 0; i < n; ++i) printf("%17s%13.4e\n", "", VR(i, j)); else if (wi[j] > 0.0) for (i = 0; i < n; ++i) printf("%18s(%11.4e, %11.4e)\n", "", VR(i, j), VR(i, j+1)); else for (i = 0; i < n; ++i) printf("%18s(%11.4e, %11.4e)\n", "", VR(i, j-1), -VR(i, j)); printf("\n"); } END: if (a) NAG_FREE(a); if (vr) NAG_FREE(vr); if (wi) NAG_FREE(wi); if (wr) NAG_FREE(wr); return exit_status; } #undef A #undef VR