/* nag_dsbevx (f08hbc) Example Program. * * Copyright 2011 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include int main(void) { /* Scalars */ double abstol, vl, vu; Integer exit_status = 0, i, il = 0, iu = 0, j, kd, m, n, pdab, pdq, pdz; /* Arrays */ char nag_enum_arg[40]; double *ab = 0, *q = 0, *w = 0, *z = 0; Integer *index = 0; /* Nag Types */ Nag_OrderType order; Nag_UploType uplo; NagError fail, fail_print; #ifdef NAG_COLUMN_MAJOR #define AB_UPPER(I, J) ab[(J - 1) * pdab + kd + I - J] #define AB_LOWER(I, J) ab[(J - 1) * pdab + I - J] order = Nag_ColMajor; #else #define AB_UPPER(I, J) ab[(I - 1) * pdab + J - I] #define AB_LOWER(I, J) ab[(I - 1) * pdab + kd + J - I] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dsbevx (f08hbc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld%ld%*[^\n]", &n, &kd); /* Read uplo */ scanf("%39s%*[^\n]", nag_enum_arg); /* nag_enum_name_to_value (x04nac). * Converts NAG enum member name to value */ uplo = (Nag_UploType) nag_enum_name_to_value(nag_enum_arg); /* Allocate memory */ if (!(ab = NAG_ALLOC((kd+1)*n, double)) || !(q = NAG_ALLOC(n*n, double)) || !(w = NAG_ALLOC(n, double)) || !(z = NAG_ALLOC(n*n, double)) || !(index = NAG_ALLOC(n, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } pdab = kd+1; pdq = n; pdz = n; /* Read the lower and upper bounds of the interval to be searched, * and read the upper or lower triangular part of the matrix A * from data file. */ scanf("%lf%lf%*[^\n]", &vl, &vu); if (uplo == Nag_Upper) { for (i = 1; i <= n; ++i) for (j = i; j <= MIN(n, i + kd); ++j) scanf("%lf", &AB_UPPER(i, j)); scanf("%*[^\n]"); } else if (uplo == Nag_Lower) { for (i = 1; i <= n; ++i) for (j = MAX(1, i - kd); j <= i; ++j) scanf("%lf", &AB_LOWER(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_dsbevx (f08hbc). * Solve the band symmetric eigenvalue problem. */ nag_dsbevx(order, Nag_DoBoth, Nag_Interval, uplo, n, kd, ab, pdab, q, pdq, vl, vu, il, iu, abstol, &m, w, z, pdz, index, &fail); if (fail.code != NE_NOERROR && fail.code != NE_CONVERGENCE) { printf("Error from nag_dsbevx (f08hbc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print solution */ printf("Number of eigenvalues found =%5ld\n", m); printf("\nEigenvalues\n"); for (j = 0; j < m; ++j) printf("%8.4f%s", w[j], (j+1)%8 == 0?"\n":" "); printf("\n\n"); /* nag_gen_real_mat_print (x04cac). * Print selected eigenvectors. */ INIT_FAIL(fail_print); fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z, pdz, "Selected eigenvectors", 0, &fail_print); if (fail_print.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail_print.message); exit_status = 1; goto END; } if (fail.code == NE_CONVERGENCE) { printf("eigenvectors failed to converge\n"); printf("Indices of eigenvectors that did not converge\n"); for (j = 0; j < m; ++j) printf("%8ld%s", index[j], (j+1)%8 == 0?"\n":" "); } END: NAG_FREE(ab); NAG_FREE(q); NAG_FREE(w); NAG_FREE(z); NAG_FREE(index); return exit_status; } #undef AB_UPPER #undef AB_LOWER