NAG Library Function Document

nag_sparse_nsym_basic_diagnostic (f11bfc)

1  Purpose

2  Specification

3  Description

4  References

5  Arguments

1:     itn – Integer *Output

On exit: the number of iterations carried out by nag_sparse_nsym_basic_solver (f11bec).

2:     stplhs – double *Output

On exit: the current value of the left-hand side of the termination criterion used by nag_sparse_nsym_basic_solver (f11bec).

3:     stprhs – double *Output

On exit: the current value of the right-hand side of the termination criterion used by nag_sparse_nsym_basic_solver (f11bec).

4:     anorm – double *Output

On exit: if $\mathbf{iterm}=1$ in the previous call to nag_sparse_nsym_basic_setup (f11bdc), then anorm contains ${‖A‖}_p$, where $p=1$, $2$ or $\infty$, either supplied or, in the case of $1$ or $\infty$, estimated by nag_sparse_nsym_basic_solver (f11bec); otherwise $\mathbf{anorm}=0.0$.

5:     sigmax – double *Output

On exit: if $\mathbf{iterm}=2$ in the previous call to nag_sparse_nsym_basic_setup (f11bdc), the current estimate of the largest singular value ${\sigma }_1\left(\stackrel{-}{A}\right)$ 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, $\mathbf{sigmax}=0.0$ 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:     lwork – IntegerInput

On entry: the dimension of the array work (see also Section 5 in nag_sparse_nsym_basic_setup (f11bdc)).

Constraint: $\mathbf{lwork}\ge 100$.

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:     fail – NagError *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 $⟨\mathit{\text{value}}⟩$ had an illegal value.

NE_INT

On entry, $\mathbf{lwork}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{lwork}\ge 100$.

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

8  Parallelism and Performance

9  Further Comments

10  Example