D02 Chapter Contents
D02 Chapter Introduction
NAG Library Manual

# NAG Library Routine DocumentD02NRF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

## 1  Purpose

D02NRF is an enquiry routine for communicating with D02NMF or D02NNF when supplying columns of a sparse Jacobian matrix.

## 2  Specification

 SUBROUTINE D02NRF ( J, IPLACE, INFORM)
 INTEGER J, IPLACE, INFORM(23)

## 3  Description

D02NRF is required when D02NMF or D02NNF is being used with sparse matrix linear algebra. After an exit from D02NMF or D02NNF with ${\mathbf{IREVCM}}=8$, D02NRF must be called to determine which column of the Jacobian is required and where it is to be placed in the array RWORK (a argument of D02NMF or D02NNF).

## 4  References

See the D02M–N Sub-chapter Introduction.

## 5  Arguments

1:     $\mathrm{J}$ – INTEGEROutput
On exit: the index $j$ of the column of the Jacobian which is required.
2:     $\mathrm{IPLACE}$ – INTEGEROutput
On exit: indicates which locations in the array RWORK to fill with the $j$th column.
If ${\mathbf{IPLACE}}=1$, the $\left(i,j\right)$th element of the Jacobian must be placed in ${\mathbf{RWORK}}\left(50+2×{\mathbf{LDYSAV}}+i\right)$, otherwise the $\left(i,j\right)$th element must be placed in ${\mathbf{RWORK}}\left(50+{\mathbf{LDYSAV}}+i\right)$.
If ${\mathbf{JCEVAL}}=\text{'F'}$, in the previous call to D02NUF, then ${\mathbf{IPLACE}}=2$ always, hence the $j$th column of the Jacobian must be placed in ${\mathbf{RWORK}}\left(50+{\mathbf{LDYSAV}}+\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,{\mathbf{NEQ}}$.
RWORK, NEQ and LDYSAV are arguments of D02NMF and D02NNF.
3:     $\mathrm{INFORM}\left(23\right)$ – INTEGER arrayCommunication Array
On entry: contains information supplied by the integrator.

None.

Not applicable.

## 8  Parallelism and Performance

D02NRF is not threaded in any implementation.