NAG Library Function Document

nag_opt_free (e04xzc)


    1  Purpose
    7  Accuracy
    10  Example


nag_opt_free (e04xzc) is the function for freeing memory allocated by a NAG C Library function to the e04 options structure, type Nag_E04_Opt. The function will only free memory which has been allocated to pointers within the options structure by an optimization function; it will not free memory you have allocated. The standard C function free() must not be used for freeing NAG allocated memory in Chapter e04.


#include <nag.h>
#include <nage04.h>
void  nag_opt_free (Nag_E04_Opt *options, const char *p_name, NagError *fail)


The optimization functions of Chapter e04 have a number of optional parameters, which are set by means of a structure of type Nag_E04_Opt. Optional parameter values can be assigned to members of the options structure directly in the program text and/or by supplying the optional values in a file to be read by the function nag_opt_read (e04xyc).
Many of the optimization functions use pointers within the options structure as arrays. The appropriate amount of memory for the arrays will be allocated internally by the optimization function being used. The same options structure may be used in several calls to an optimization function: NAG allocated memory will be automatically freed and reallocated on each call to the optimization function. This is the recommended method of use of the pointers within the options structure.
If users wish to free NAG allocated memory from the options structure at any point in their program, then nag_opt_free (e04xzc) must be used to perform the freeing operation.
Memory may be allocated to the pointers in the options structure if the NAG default memory allocation is not wanted — nag_opt_free (e04xzc) will not free this user allocated memory. Dynamic memory allocated by you should be freed by the standard C library function free(). If it is intended to re-enter a NAG optimization function after this use of free(), with the intention of using the NAG default memory allocation, then the pointer involved must be set to NULL before re-entry.
The purpose of using nag_opt_free (e04xzc) to free NAG allocated memory instead of free() is to allow the optimization functions to maintain knowledge of which pointers have been allocated memory by a NAG function and you have allocated memory. If nag_opt_free (e04xzc) is not used to free the NAG allocated memory and the standard C function free() is used instead then there is the danger that any memory which is dynamically allocated will be freed by the optimization function.
To conserve memory nag_opt_free (e04xzc) should also be used to free NAG allocated memory within the options structure when that memory is no longer required, e.g., before returning from the function which calls the NAG C Library Chapter e04 functions. Any memory not freed will, of course, be freed when your program terminates.




1:     options Nag_E04_Opt *Input/Output
On entry: the options structure that was used in a call to an optimization function in Chapter e04. The pointers within the structure may have either NAG allocated memory or user allocated memory.
On exit: those pointers selected (see argument p_name) which pointed to NAG allocated memory will have been freed and set to NULL. Any user allocated memory will not be freed.
2:     p_name const char *Input
On entry: a character string specifying which pointer is to be freed. The string should give the optional parameter or structure member name. If you wish to free all NAG allocated memory then an empty string "" or the string "all" should be given. Please note that p_name is case sensitive and as such upper-case letters should not be used unless explicitly required.
3:     fail NagError *Input/Output
The NAG error argument (see Section 3.7 in How to Use the NAG Library and its Documentation).

Error Indicators and Warnings

String supplied, string , does not match name of any pointer in the options structure.


Not applicable.

Parallelism and Performance

nag_opt_free (e04xzc) is not threaded in any implementation.

Further Comments



See Section 10 in nag_opt_lsq_no_deriv (e04fcc), nag_opt_lsq_deriv (e04gbc), nag_opt_lp (e04mfc), nag_opt_qp (e04nfc), nag_opt_nlp_solve (e04wdc) and nag_opt_lsq_covariance (e04ycc).
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017