nag_sparse_nsym_basic_diagnostic (f11bfc) (PDF version)
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NAG C Library Manual

NAG Library Function Document

nag_sparse_nsym_basic_diagnostic (f11bfc)

+ Contents

    1  Purpose
    7  Accuracy
    9  Example

1  Purpose

nag_sparse_nsym_basic_diagnostic (f11bfc) is the third in a suite of three functions for the iterative solution of a real general (nonsymmetric) system of simultaneous linear equations (see Golub and Van Loan (1996)). nag_sparse_nsym_basic_diagnostic (f11bfc) returns information about the computations during an iteration and/or after this has been completed. The first function of the suite, nag_sparse_nsym_basic_setup (f11bdc), is a setup function; the second function, nag_sparse_nsym_basic_solver (f11bec), is the iterative solver itself.
These three functions are suitable for the solution of large sparse general (nonsymmetric) systems of equations.

2  Specification

#include <nag.h>
#include <nagf11.h>
void  nag_sparse_nsym_basic_diagnostic (Integer *itn, double *stplhs, double *stprhs, double *anorm, double *sigmax, const double work[], Integer lwork, NagError *fail)

3  Description

nag_sparse_nsym_basic_diagnostic (f11bfc) returns information about the solution process. It can be called either during a monitoring step of nag_sparse_nsym_basic_solver (f11bec) or after nag_sparse_nsym_basic_solver (f11bec) has completed its tasks. Calling nag_sparse_nsym_basic_diagnostic (f11bfc) at any other time will result in an error condition being raised.
For further information you should read the documentation for nag_sparse_nsym_basic_setup (f11bdc) and nag_sparse_nsym_basic_solver (f11bec).

4  References

Golub G H and Van Loan C F (1996) Matrix Computations (3rd Edition) Johns Hopkins University Press, Baltimore

5  Arguments

1:     itnInteger *Output
On exit: the number of iterations carried out by nag_sparse_nsym_basic_solver (f11bec).
2:     stplhsdouble *Output
On exit: the current value of the left-hand side of the termination criterion used by nag_sparse_nsym_basic_solver (f11bec).
3:     stprhsdouble *Output
On exit: the current value of the right-hand side of the termination criterion used by nag_sparse_nsym_basic_solver (f11bec).
4:     anormdouble *Output
On exit: if iterm=1 in the previous call to nag_sparse_nsym_basic_setup (f11bdc) then anorm contains Ap, where p=1, 2 or , either supplied or, in the case of 1 or  estimated by nag_sparse_nsym_basic_solver (f11bec); otherwise anorm=0.0.
5:     sigmaxdouble *Output
On exit: if iterm=2 in the previous call to nag_sparse_nsym_basic_setup (f11bdc), the current estimate of the largest singular value σ1A- of the preconditioned iteration matrix, either when it has been supplied to nag_sparse_nsym_basic_setup (f11bdc) or it has been estimated by nag_sparse_nsym_basic_solver (f11bec) (see also Sections 3 and 5 in nag_sparse_nsym_basic_setup (f11bdc)); otherwise, sigmax=0.0 is returned.
6:     work[lwork]const doubleCommunication Array
On entry: the array work as returned by nag_sparse_nsym_basic_solver (f11bec) (see also Sections 3 and 5 in nag_sparse_nsym_basic_solver (f11bec)).
7:     lworkIntegerInput
On entry: the dimension of the array work (see also Section 5 in nag_sparse_nsym_basic_setup (f11bdc)).
Constraint: lwork100.
Note: although the minimum value of lwork ensures the correct functioning of nag_sparse_nsym_basic_diagnostic (f11bfc), a larger value is required by the iterative solver nag_sparse_nsym_basic_solver (f11bec) (see also Section 5 in nag_sparse_nsym_basic_setup (f11bdc)).
8:     failNagError *Input/Output
The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

NE_BAD_PARAM
On entry, argument number value had an illegal value.
On entry, argument value had an illegal value.
NE_INT
On entry, lwork=value.
Constraint: lwork100.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
NE_OUT_OF_SEQUENCE
nag_sparse_nsym_basic_diagnostic (f11bfc) has been called out of sequence.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

See Section 9 in nag_sparse_nsym_basic_setup (f11bdc).

nag_sparse_nsym_basic_diagnostic (f11bfc) (PDF version)
f11 Chapter Contents
f11 Chapter Introduction
NAG C Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012