The routine may be called by the names d02pjf or nagf_ode_ivp_rk_interp_eval.
When integrating using the reverse communication Runge–Kutta integrator d02pgf, the solution or its derivatives can be obtained inexpensively between steps by interpolation. d02phf is called after a step by d02pgf from a previous value of () to its current value, (i.e., a th successful time-step has been taken). d02pjf can then be called to evaluate interpolated approximations of the function or its derivatives at any value of in the interval .
Brankin R W, Gladwell I and Shampine L F (1991) RKSUITE: A suite of Runge–Kutta codes for the initial value problems for ODEs SoftReport 91-S1 Southern Methodist University
1: – IntegerInput
On entry: indicates whether consistency checks on input arguments should be performed
Don't perform checks on input arguments.
Perform consistency checks on input arguments.
It is recommended to use on the first call following a call to d02phf and to set on subsequent calls within the last step to avoid the overhead of argument checking.
2: – IntegerInput
On entry: , the dimension of the system of ODEs being integrated.
this must be the same value as supplied in a previous call to d02pqf.
3: – IntegerInput
On entry: only the first nwant system components to be computed. This should be the same value as passed to d02phf when computing the interpolant.
On entry: , the value of the independent variable where a solution is desired. Although any value of can be supplied, accurate solutions can only be obtained for values in the range of the last time-step taken by d02pgf.
5: – IntegerInput
Compute approximations to the first nwant components of the solution .
Compute approximations to the first nwant components of the first derivatives of the solution .
On entry: these must be the same arrays supplied in a previous call d02pgf. They must remain unchanged between calls.
On exit: information about the integration for use on subsequent calls to d02pgf, d02phf or other associated routines.
11: – IntegerInput/Output
On entry: ifail must be set to , or to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of means that an error message is printed while a value of means that it is not.
If halting is not appropriate, the value or is recommended. If message printing is undesirable, then the value is recommended. Otherwise, the value is recommended. When the value or is used it is essential to test the value of ifail on exit.
On exit: unless the routine detects an error or a warning has been flagged (see Section 6).
6Error Indicators and Warnings
If on entry or , explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
On entry, a previous call to the setup routine 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.
On entry, . Constraint: or .
On entry, , and . Constraint: for or , .
On entry, . Constraint: for or , .
On entry, and . Constraint: for or , .
On entry, , but the value passed to the setup routine was .
On entry, , but on interpolation setup . Constraint: nwant must be unchanged from setup.
The previous call to the interpolation setup routine returned an error.
You cannot call this routine before you have called the interpolation setup.
An unexpected error has been triggered by this routine. Please
See Section 7 in the Introduction to the NAG Library FL Interface for further information.
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.
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.
The computed values will be of a similar accuracy to that computed by d02pgf.