/* nag_dsyevr (f08fdc) Example Program. * * Copyright 2011 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include int main(void) { /* Scalars */ double abstol, vl = 0.0, vu = 0.0; Integer exit_status = 0, i, il, iu, j, m, n; Integer pda, pdz; /* Arrays */ double *a = 0, *w = 0, *z = 0; Integer *isuppz = 0; /* Nag Types */ Nag_OrderType order; NagError fail; #ifdef NAG_COLUMN_MAJOR #define A(I, J) a[(J - 1) * pda + I - 1] #define Z(I, J) z[(J - 1) * pdz + I - 1] order = Nag_ColMajor; #else #define A(I, J) a[(I - 1) * pda + J - 1] #define Z(I, J) z[(I - 1) * pdz + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dsyevr (f08fdc) Example Program Results\n\n"); /* Skip heading in data file and read n and the lower and upper * indices of the smallest and largest eigenvalues to be found */ scanf("%*[^\n]"); scanf("%ld%ld%ld%*[^\n]", &n, &il, &iu); m = iu - il + 1; /* Allocate memory */ if (!(a = NAG_ALLOC(n*n, double)) || !(w = NAG_ALLOC(n, double)) || !(z = NAG_ALLOC(n*n, double)) || !(isuppz = NAG_ALLOC(m*2, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } pda = n; pdz = n; /* Read the upper triangular part of the matrix A from data file */ for (i = 1; i <= n; ++i) for (j = i; j <= n; ++j) scanf("%lf", &A(i, j)); scanf("%*[^\n]"); /* Set the absolute error tolerance for eigenvalues. With abstol * set to zero, the default value is used instead. */ abstol = 0.0; /* nag_dsyevr (f08fdc). * Solve the symmetric eigenvalue problem. */ nag_dsyevr(order, Nag_DoBoth, Nag_Indices, Nag_Upper, n, a, pda, vl, vu, il, iu, abstol, &m, w, z, pdz, isuppz, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dsyevr (f08fdc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Normalize the eigenvectors */ for(j=1; j<=m; j++) for(i=n; i>=1; i--) Z(i, j) = Z(i, j) / Z(1,j); /* Print solution */ printf("Selected eigenvalues\n"); for (j = 0; j < m; ++j) printf("%8.4f%s", w[j], (j+1)%8 == 0?"\n":" "); printf("\n"); /* nag_gen_real_mat_print (x04cac). * Print selected eigenvectors. */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z, pdz, "Selected eigenvectors", 0, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; } END: if (a) NAG_FREE(a); if (w) NAG_FREE(w); if (z) NAG_FREE(z); if (isuppz) NAG_FREE(isuppz); return exit_status; } #undef A #undef Z