d02npf is a setup routine which you must call prior to d02nef and after a call to d02mwf, if the Jacobian is to be considered as having a banded structure.

2 Specification

Fortran Interface

Subroutine d02npf (

neq, ml, mu, icom, licom, ifail)

Integer, Intent (In)	::	neq, ml, mu, licom
Integer, Intent (Inout)	::	icom(licom), ifail

C Header Interface

#include <nag.h>

void	d02npf_ (const Integer neq, const Integer ml, const Integer mu, Integer icom[], const Integer licom, Integer *ifail)

The routine may be called by the names d02npf or nagf_ode_dae_dassl_linalg.

3 Description

A call to d02npf specifies that the Jacobian to be used is banded in structure. If d02npf is not called before a call to d02nef then the Jacobian is assumed to be full.

4 References

None.

5 Arguments

1: $neq$ – Integer Input: On entry: the number of differential-algebraic equations to be solved.

Constraint: $1 \leq neq$ .
2: $ml$ – Integer Input: On entry: $m_{L}$ , the number of subdiagonals in the band.

Constraint: $0 \leq ml \leq neq - 1$ .
3: $mu$ – Integer Input: On entry: $m_{U}$ , the number of superdiagonals in the band.

Constraint: $0 \leq mu \leq neq - 1$ .
4: $icom (licom)$ – Integer array Communication Array: icom is used to communicate details of the integration from d02mwf and details of the banded structure of the Jacobian to d02nef.
5: $licom$ – Integer Input: On entry: the dimension of the array icom as declared in the (sub)program from which d02npf is called.

Constraint: $licom \geq 50 + neq$ .
6: $ifail$ – Integer Input/Output: On entry: ifail must be set to $0$ , $−1$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $−1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $−1$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $- 1$ or $1$ is used it is essential to test the value of ifail on exit.

On exit: $ifail = 0$ unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry

ifail = 0

−1

, explanatory error messages are output on the current error message unit (as defined by x04aaf).

Errors or warnings detected by the routine:

$ifail = 1$: On entry, $neq = ⟨ value ⟩$ .
Constraint: $neq \geq 1$ .

$ifail = 2$: On entry, $ml = ⟨ value ⟩$ .
Constraint: $ml \geq 0$ .

On entry, $ml = ⟨ value ⟩$ and $neq = ⟨ value ⟩$ .
Constraint: $ml \leq neq - 1$ .

$ifail = 3$: On entry, $mu = ⟨ value ⟩$ .
Constraint: $mu \geq 0$ .

On entry, $mu = ⟨ value ⟩$ and $neq = ⟨ value ⟩$ .
Constraint: $mu \leq neq - 1$ .

$ifail = 4$: Either the initialization routine has not been called prior to the first call of this routine or the communication array has become corrupted.

$ifail = 5$: On entry, licom is too small: $licom = ⟨ value ⟩$ .

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.