NAG Library Function Document

nag_sparse_nsym_precon_ilu_solve (f11dbc)

1  Purpose

2  Specification

3  Description

4  References

5  Arguments

1:    $\mathbf{trans}$ – Nag_TransTypeInput

On entry: specifies whether or not the matrix $M$ is transposed.

$\mathbf{trans}=\mathrm{Nag\_NoTrans}$

$Mx=y$ is solved.

$\mathbf{trans}=\mathrm{Nag\_Trans}$

$M^{\mathrm{T}}x=y$ is solved.

Constraint: $\mathbf{trans}=\mathrm{Nag\_NoTrans}$ or $\mathrm{Nag\_Trans}$.

2:    $\mathbf{n}$ – IntegerInput

On entry: $n$, the order of the matrix $M$. This must be the same value as was supplied in the preceding call to nag_sparse_nsym_fac (f11dac).

Constraint: $\mathbf{n}\ge 1$.

3:    $\mathbf{a}\left[\mathbf{la}\right]$ – const doubleInput

On entry: the values returned in the array a by a previous call to nag_sparse_nsym_fac (f11dac).

4:    $\mathbf{la}$ – IntegerInput

On entry: the dimension of the arrays a, irow and icol. This must be the same value returned by the preceding call to nag_sparse_nsym_fac (f11dac).

5:    $\mathbf{irow}\left[\mathbf{la}\right]$ – const IntegerInput

6:    $\mathbf{icol}\left[\mathbf{la}\right]$ – const IntegerInput

7:    $\mathbf{ipivp}\left[\mathbf{n}\right]$ – const IntegerInput

8:    $\mathbf{ipivq}\left[\mathbf{n}\right]$ – const IntegerInput

9:    $\mathbf{istr}\left[\mathbf{n}+1\right]$ – const IntegerInput

10:  $\mathbf{idiag}\left[\mathbf{n}\right]$ – const IntegerInput

On entry: the values returned in arrays irow, icol, ipivp, ipivq, istr and idiag by a previous call to nag_sparse_nsym_fac (f11dac).

11:  $\mathbf{check}$ – Nag_SparseNsym_CheckDataInput

On entry: specifies whether or not the CS representation of the matrix $M$ should be checked.

$\mathbf{check}=\mathrm{Nag\_SparseNsym\_Check}$

Checks are carried on the values of n, irow, icol, ipivp, ipivq, istr and idiag.

$\mathbf{check}=\mathrm{Nag\_SparseNsym\_NoCheck}$

None of these checks are carried out.

See also Section 9.2.

Constraint: $\mathbf{check}=\mathrm{Nag\_SparseNsym\_Check}$ or $\mathrm{Nag\_SparseNsym\_NoCheck}$.

12:  $\mathbf{y}\left[\mathbf{n}\right]$ – const doubleInput

On entry: the right-hand side vector $y$.

13:  $\mathbf{x}\left[\mathbf{n}\right]$ – doubleOutput

On exit: the solution vector $x$.

14:  $\mathbf{fail}$ – NagError *Input/Output

The NAG error argument (see Section 2.7 in How to Use the NAG Library and its Documentation).

6  Error Indicators and Warnings

NE_ALLOC_FAIL

Dynamic memory allocation failed.
See Section 2.3.1.2 in How to Use the NAG Library and its Documentation for further information.

NE_BAD_PARAM

On entry, argument $〈\mathit{\text{value}}〉$ had an illegal value.

NE_INT

On entry, $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{n}\ge 1$.

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.

An unexpected error has been triggered by this function. Please contact NAG.
See Section 2.7.6 in How to Use the NAG Library and its Documentation for further information.

NE_INVALID_CS

On entry, $i=〈\mathit{\text{value}}〉$, $\mathbf{icol}\left[i-1\right]=〈\mathit{\text{value}}〉$, and $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{icol}\left[i-1\right]\ge 1$ and $\mathbf{icol}\left[i-1\right]\le \mathbf{n}$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, $i=〈\mathit{\text{value}}〉$, $\mathbf{irow}\left[i-1\right]=〈\mathit{\text{value}}〉$, $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{irow}\left[i-1\right]\ge 1$ and $\mathbf{irow}\left[i-1\right]\le \mathbf{n}$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

NE_INVALID_CS_PRECOND

On entry, $\mathbf{idiag}\left[i-1\right]$ appears to be incorrect: $i=〈\mathit{\text{value}}〉$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, istr appears to be invalid.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, $\mathbf{istr}\left[i-1\right]$ is inconsistent with irow: $i=〈\mathit{\text{value}}〉$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

NE_INVALID_ROWCOL_PIVOT

On entry, $i=〈\mathit{\text{value}}〉$, $\mathbf{ipivp}\left[i-1\right]=〈\mathit{\text{value}}〉$, $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{ipivp}\left[i-1\right]\ge 1$ and $\mathbf{ipivp}\left[i-1\right]\le \mathbf{n}$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, $i=〈\mathit{\text{value}}〉$, $\mathbf{ipivq}\left[i-1\right]=〈\mathit{\text{value}}〉$, $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{ipivq}\left[i-1\right]\ge 1$ and $\mathbf{ipivq}\left[i-1\right]\le \mathbf{n}$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, $\mathbf{ipivp}\left[i-1\right]$ is a repeated value: $i=〈\mathit{\text{value}}〉$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, $\mathbf{ipivq}\left[i-1\right]$ is a repeated value: $i=〈\mathit{\text{value}}〉$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

NE_NO_LICENCE

Your licence key may have expired or may not have been installed correctly.
See Section 2.7.5 in How to Use the NAG Library and its Documentation for further information.

NE_NOT_STRICTLY_INCREASING

On entry, $\mathbf{a}\left[i-1\right]$ is out of order: $i=〈\mathit{\text{value}}〉$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

On entry, the location ($\mathbf{irow}\left[i-1\right],\mathbf{icol}\left[i-1\right]$) is a duplicate: $i=〈\mathit{\text{value}}〉$.
Check that a, irow, icol, ipivp, ipivq, istr and idiag have not been corrupted between calls to nag_sparse_nsym_precon_ilu_solve (f11dbc) and nag_sparse_nsym_fac (f11dac).

7  Accuracy

8  Parallelism and Performance

9  Further Comments

9.1  Timing

9.2  Use of check

10  Example

10.1  Program Text

Program Text (f11dbce.c)

10.2  Program Data

Program Data (f11dbce.d)

10.3  Program Results

Program Results (f11dbce.r)