/* nag_det_real_band_sym (f03bhc) Example Program. * * Copyright 2011, Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include #include int main(void) { /* Scalars */ Integer exit_status = 0; Integer i, id, j, kd, kl, ku, k, n, pdab; double d; /* Arrays */ char nag_enum_arg[40]; double *ab = 0; /* NAG types */ NagError fail; Nag_UploType uplo; Nag_OrderType order; printf("nag_det_real_band_sym (f03bhc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%"NAG_IFMT "%"NAG_IFMT "%*[^\n]", &n, &kd); k = kd + 1; pdab = k; if (!(ab = NAG_ALLOC(k*n, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } scanf("%s %*[^\n] ", nag_enum_arg); uplo = (Nag_UploType) nag_enum_name_to_value(nag_enum_arg); /* Define matrix element A_ij in terms of elements of array ab[] */ #ifdef NAG_COLUMN_MAJOR #define AB_UPPER(I, J) ab[(J-1)*pdab + k + I - J - 1] #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 + k + J - I - 1] order = Nag_RowMajor; #endif if (uplo == Nag_Upper) { /* Read in upper triangular banded matrix */ ku = kd; kl = 0; for (i = 1; i <= n; i++) for (j = i; j <= MIN(i + kd, n); j++) scanf("%lf", &AB_UPPER(i,j)); scanf("%*[^\n] "); } else if (uplo == Nag_Lower) { /* Read in lower triangular banded matrix */ ku = 0; kl = kd; for (i = 1; i <= n; i++) for (j = MAX(1, i - kd); j <= i; j++) scanf("%lf", &AB_LOWER(i,j)); scanf("%*[^\n] "); } INIT_FAIL(fail); /* Facrtorize A using nag_dpbtrf (f07hdc) * Cholesky factorization of real symmetric positive definite band matrix */ nag_dpbtrf(order, uplo, n, kd, ab, pdab, &fail); if (fail.code != NE_NOERROR) { printf("%s\n", fail.message); exit_status = 1; goto END; } /* nag_band_real_mat_print (x04cec) * Print real packed banded matrix (easy-to-use) */ fflush(stdout); nag_band_real_mat_print(order, n, n, kl, ku, ab, pdab, "Array ab after factorization", NULL, &fail); if (fail.code != NE_NOERROR) { printf("%s\n", fail.message); exit_status = 2; goto END; } /* nag_det_real_band_sym (f03bhc) * Determinant of real symmetric positive definite banded matrix */ nag_det_real_band_sym(order, uplo, n, kd, ab, pdab, &d, &id, &fail); if (fail.code != NE_NOERROR) { printf("%s\n", fail.message); exit_status = 3; goto END; } printf("\nd = %12.5f id = %10" NAG_IFMT "\n", d, id); printf("Value of determinant = %13.5e\n", d*pow(2.0, id)); END: if (ab) NAG_FREE(ab); return exit_status; }