NAG C Library Function Document

nag_ode_ivp_rkts_diag (d02ptc)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:    $\mathbf{fevals}$ – Integer *Output

On exit: the total number of evaluations of $f$ used in the integration so far; this includes evaluations of $f$ required for the secondary integration necessary if nag_ode_ivp_rkts_setup (d02pqc) had previously been called with $\mathbf{errass}=\mathrm{Nag\_ErrorAssess\_on}$.

2:    $\mathbf{stepcost}$ – Integer *Output

On exit: the cost in terms of number of evaluations of $f$ of a typical step with the method being used for the integration. The method is specified by the argument method in a prior call to nag_ode_ivp_rkts_setup (d02pqc).

3:    $\mathbf{waste}$ – double *Output

On exit: the number of attempted steps that failed to meet the local error requirement divided by the total number of steps attempted so far in the integration. A ‘large’ fraction indicates that the integrator is having trouble with the problem being solved. This can happen when the problem is ‘stiff’ and also when the solution has discontinuities in a low-order derivative.

4:    $\mathbf{stepsok}$ – Integer *Output

On exit: the number of accepted steps.

5:    $\mathbf{hnext}$ – double *Output

On exit: the step size the integrator will attempt to use for the next step.

6:    $\mathbf{iwsav}\left[130\right]$ – IntegerCommunication Array

7:    $\mathbf{rwsav}\left[350\right]$ – const doubleCommunication Array

Note: the communication rwsav used by the other functions in the suite must be used here however, only the first $350$ elements will be referenced.

On entry: these must be the same arrays supplied in a previous call to nag_ode_ivp_rkts_range (d02pec), nag_ode_ivp_rkts_onestep (d02pfc) or nag_ode_ivp_rk_step_revcomm (d02pgc). They must remain unchanged between calls.

On exit: information about the integration for use on subsequent calls to nag_ode_ivp_rkts_range (d02pec), nag_ode_ivp_rkts_onestep (d02pfc) or nag_ode_ivp_rk_step_revcomm (d02pgc) or other associated functions.

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

The NAG error argument (see Section 3.7 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_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.
See Section 2.7.6 in How to Use the NAG Library and its Documentation for further information.

NE_MISSING_CALL

You cannot call this function before you have called the integrator.

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_PREV_CALL

On entry, a previous call to the setup function has not been made or the communication arrays have become corrupted, or a catastrophic error has already been detected elsewhere.
You cannot continue integrating the problem.

NE_RK_INVALID_CALL

You have already made one call to this function after the integrator could not achieve specified accuracy.
You cannot call this function again.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example