NAG Library Function Document

nag_ode_ivp_rkts_diag (d02ptc)

1  Purpose

2  Specification

3  Description

4  References

5  Arguments

1:     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:     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:     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:     stepsok – Integer *Output

On exit: the number of accepted steps.

5:     hnext – double *Output

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

6:     iwsav[$130$] – IntegerCommunication Array

7:     rwsav[$350$] – 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) or nag_ode_ivp_rkts_onestep (d02pfc). They must remain unchanged between calls.

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

8:     fail – NagError *Input/Output

The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

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.

NE_MISSING_CALL

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

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