/* nag_dpbcon (f07hgc) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include #include int main(void) { /* Scalars */ Integer i, j, k, kd, n, pdab; Integer exit_status=0; double anorm, rcond; NagError fail; Nag_UploType uplo_enum; Nag_OrderType order; /* Arrays */ char uplo[2]; 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); Vprintf("nag_dpbcon (f07hgc) Example Program Results\n\n"); /* Skip heading in data file */ Vscanf("%*[^\n] "); Vscanf("%ld%ld%*[^\n] ", &n, &kd); pdab = kd + 1; /* Allocate memory */ if ( !(ab = NAG_ALLOC((kd+1) * n, double)) ) { Vprintf("Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ Vscanf(" ' %1s '%*[^\n] ", uplo); if (*(unsigned char *)uplo == 'L') uplo_enum = Nag_Lower; else if (*(unsigned char *)uplo == 'U') uplo_enum = Nag_Upper; else { Vprintf("Unrecognised character for Nag_UploType type\n"); exit_status = -1; goto END; } k = kd + 1; if (uplo_enum == Nag_Upper) { for (i = 1; i <= n; ++i) { for (j = i; j <= MIN(i+kd,n); ++j) Vscanf("%lf", &AB_UPPER(i,j)); } Vscanf("%*[^\n] "); } else { for (i = 1; i <= n; ++i) { for (j = MAX(1,i-kd); j <= i; ++j) Vscanf("%lf", &AB_LOWER(i,j)); } Vscanf("%*[^\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_enum, n, kd, ab, pdab, &anorm, &fail); if (fail.code != NE_NOERROR) { Vprintf("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_enum, n, kd, ab, pdab, &fail); if (fail.code != NE_NOERROR) { Vprintf("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_enum, n, kd, ab, pdab, anorm, &rcond, &fail); if (fail.code != NE_NOERROR) { Vprintf("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) Vprintf("Estimate of condition number =%10.2e\n\n", 1.0/rcond); else Vprintf("A is singular to working precision\n"); END: if (ab) NAG_FREE(ab); return exit_status; }