/* nag_dpbcon (f07hgc) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include #include #include int main(int argc, char *argv[]) { FILE *fpin, *fpout; /* Scalars */ Integer i, j, k, kd, n, pdab; Integer exit_status = 0; double anorm, rcond; NagError fail; Nag_UploType uplo; Nag_OrderType order; /* Arrays */ char nag_enum_arg[40]; double *ab = 0; #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 INIT_FAIL(fail); /* Check for command-line IO options */ fpin = nag_example_file_io(argc, argv, "-data", NULL); fpout = nag_example_file_io(argc, argv, "-results", NULL); fprintf(fpout, "nag_dpbcon (f07hgc) Example Program Results\n\n"); /* Skip heading in data file */ fscanf(fpin, "%*[^\n] "); fscanf(fpin, "%ld%ld%*[^\n] ", &n, &kd); pdab = kd + 1; /* Allocate memory */ if (!(ab = NAG_ALLOC((kd+1) * n, double))) { fprintf(fpout, "Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ fscanf(fpin, " %s%*[^\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); k = kd + 1; if (uplo == Nag_Upper) { for (i = 1; i <= n; ++i) { for (j = i; j <= MIN(i+kd, n); ++j) fscanf(fpin, "%lf", &AB_UPPER(i, j)); } fscanf(fpin, "%*[^\n] "); } else { for (i = 1; i <= n; ++i) { for (j = MAX(1, i-kd); j <= i; ++j) fscanf(fpin, "%lf", &AB_LOWER(i, j)); } fscanf(fpin, "%*[^\n] "); } /* Compute norm of A */ /* nag_dsb_norm (f16rec). * 1-norm, infinity-norm, Frobenius norm, largest absolute * element, real symmetric band matrix */ nag_dsb_norm(order, Nag_OneNorm, uplo, n, kd, ab, pdab, &anorm, &fail); if (fail.code != NE_NOERROR) { fprintf(fpout, "Error from nag_dsb_norm (f16rec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Factorize A */ /* 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) { fprintf(fpout, "Error from nag_dpbtrf (f07hdc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Estimate condition number */ /* nag_dpbcon (f07hgc). * Estimate condition number of real symmetric * positive-definite band matrix, matrix already factorized * by nag_dpbtrf (f07hdc) */ nag_dpbcon(order, uplo, n, kd, ab, pdab, anorm, &rcond, &fail); if (fail.code != NE_NOERROR) { fprintf(fpout, "Error from nag_dpbcon (f07hgc).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_machine_precision (x02ajc). * The machine precision */ if (rcond >= X02AJC) fprintf(fpout, "Estimate of condition number =%11.2e\n\n", 1.0/rcond); else fprintf(fpout, "A is singular to working precision\n"); END: if (fpin != stdin) fclose(fpin); if (fpout != stdout) fclose(fpout); if (ab) NAG_FREE(ab); return exit_status; }