d02nyf is a diagnostic routine which you may call either after any user-specified exit or after a mid-integration error exit from any of those integrators in Sub-chapter D02M–N that use methods set up by calls to d02mvf, d02nvf or d02nwf.

2 Specification

Fortran Interface

Subroutine d02nyf (

neq, neqmax, hu, h, tcur, tolsf, rwork, nst, nre, nje, nqu, nq, niter, imxer, algequ, inform, ifail)

Integer, Intent (In)	::	neq, neqmax, inform(23)
Integer, Intent (Inout)	::	ifail
Integer, Intent (Out)	::	nst, nre, nje, nqu, nq, niter, imxer
Real (Kind=nag_wp), Intent (In)	::	rwork(50+4*neq)
Real (Kind=nag_wp), Intent (Out)	::	hu, h, tcur, tolsf
Logical, Intent (Out)	::	algequ(neq)

C Header Interface

#include <nag.h>

void	d02nyf_ (const Integer neq, const Integer neqmax, double hu, double h, double tcur, double tolsf, const double rwork[], Integer nst, Integer nre, Integer nje, Integer nqu, Integer nq, Integer niter, Integer imxer, logical algequ[], const Integer inform[], Integer ifail)

The routine may be called by the names d02nyf or nagf_ode_ivp_stiff_integ_diag.

3 Description

d02nyf permits you to inspect statistics produced by any integrator in this sub-chapter that has been set up a call to one of d02mvf, d02nvf or d02nwf. These statistics concern the integration only.

4 References

See the D02M–N Sub-chapter Introduction.

5 Arguments

1: $neq$ – Integer Input: On entry: the value used for the argument neq when calling the integrator.

Constraint: $neq \geq 1$ .
2: $neqmax$ – Integer Input: On entry: the value used for the argument neqmax when calling the integrator.

Constraint: $neqmax \geq neq$ .
3: $hu$ – Real (Kind=nag_wp) Output: On exit: the last successful step size.
4: $h$ – Real (Kind=nag_wp) Output: On exit: the proposed next step size for continuing the integration.
5: $tcur$ – Real (Kind=nag_wp) Output: On exit: $t$ , the value of the independent variable which the integrator has actually reached. tcur will always be at least as far as the output value of the argument $t$ in the direction of integration, but may be further (if overshooting and interpolation at tout was specified, e.g., see d02nbf).
6: $tolsf$ – Real (Kind=nag_wp) Output: On exit: a tolerance scale factor, $tolsf \geq 1.0$ , which is computed when a request for too much accuracy is detected by the integrator (indicated by a return with $ifail = 3$ or $14$ ). If itol is left unaltered but rtol and atol are uniformly scaled up by a factor of tolsf the next call to the integrator is deemed likely to succeed.
7: $rwork (50 + 4 \times neq)$ – Real (Kind=nag_wp) array Communication Array: On entry: contains information supplied by the integrator.
8: $nst$ – Integer Output: On exit: the number of steps taken in the integration so far.
9: $nre$ – Integer Output: On exit: the number of function or residual evaluations (fcn (e.g., see d02nbf) or resid (e.g., see d02ngf) calls) used in the integration so far.
10: $nje$ – Integer Output: On exit: the number of Jacobian evaluations used in the integration so far. This equals the number of matrix $L U$ decompositions.
11: $nqu$ – Integer Output: On exit: the order of the method last used (successfully) in the integration.
12: $nq$ – Integer Output: On exit: the proposed order of the method for continuing the integration.
13: $niter$ – Integer Output: On exit: the number of iterations performed in the integration so far by the nonlinear equation solver.
14: $imxer$ – Integer Output: On exit: the index of the component of largest magnitude in the weighted local error vector $(e_{i} / w_{i})$ , for $i = 1, 2, \dots, neq$ .
15: $algequ (neq)$ – Logical array Output: On exit: $algequ (i) = .TRUE.$ if the $i$ th equation integrated was detected to be algebraic, otherwise $algequ (i) = .FALSE.$ . Note that when the integrators for explicit equations are being used, then $algequ (i) = .FALSE.$ , for $i = 1, 2, \dots, neq$ .
16: $inform (23)$ – Integer array Communication Array: On entry: contains information supplied by the integrator.
17: $ifail$ – 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: $neq \geq 1$ .

On entry, $neq = ⟨ value ⟩$ and $neqmax = ⟨ value ⟩$ .
Constraint: $neq \leq neqmax$ .

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

$ifail = - 99$: 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.