Each initialized problem handle (e.g., by f12jaf) should be deallocated to avoid memory leaks. Therefore, f12jzf should be called on all the handles which are no longer needed, typically after obtaining results from the solver. Please note that passing a handle which has not been properly initialized might cause unpredictable behaviour, including a crash of your program. See Section 5 in the F12 Chapter Introduction for more details about the NAG FEAST suite.

4 References

Polizzi E (2009) Density-Matrix-Based Algorithms for Solving Eigenvalue Problems Phys. Rev. B. 79 115112

5 Arguments

1: $handle$ – Type (c_ptr) Input/Output: On entry: the handle to the problem. It needs to be initialized (e.g., by f12jaf) and to hold a problem formulation compatible with f12jzf. It must not be changed between calls to the NAG FEAST suite.

On exit: the handle is destroyed and set to c_null_ptr.
2: $ifail$ – Integer Input/Output: On entry: ifail must be set to $0$ , $−1$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $−1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $−1$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $- 1$ or $1$ is used it is essential to test the value of ifail on exit.

On exit: $ifail = 0$ unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry

ifail = 0

−1

, explanatory error messages are output on the current error message unit (as defined by x04aaf).

Errors or warnings detected by the routine:

$ifail = 1$: The supplied handle was not initialized or has become corrupted.

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 399$: 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.