e04xzc is the function for freeing memory allocated by a NAG 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.
The function may be called by the names: e04xzc or nag_opt_free.
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 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 e04xzcmust 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 — 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 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 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 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 Library Chapter E04 functions. Any memory not freed will, of course, be freed when your program terminates.
1: – 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: – 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: – NagError *Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).
6Error Indicators and Warnings
String supplied, , does not match name of any pointer in the options structure.
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.