naginterfaces.library.sparse.real_​gen_​basic_​diag

naginterfaces.library.sparse.real_gen_basic_diag(comm)

real_gen_basic_diag is the third in a suite of three functions for the iterative solution of a real general (nonsymmetric) system of simultaneous linear equations (see Golub and Van Loan (1996)). real_gen_basic_diag returns information about the computations during an iteration and/or after this has been completed. The first function of the suite, real_gen_basic_setup(), is a setup function; the second function, real_gen_basic_solver(), is the iterative solver itself.

These three functions are suitable for the solution of large sparse general (nonsymmetric) systems of equations.

For full information please refer to the NAG Library document for f11bf

https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f11/f11bff.html

Parameters

commdict, communication object

Communication structure.

This argument must have been initialized by a prior call to real_gen_basic_setup().

Returns

itnint

The number of iterations carried out by real_gen_basic_solver().

stplhsfloat

The current value of the left-hand side of the termination criterion used by real_gen_basic_solver().

stprhsfloat

The current value of the right-hand side of the termination criterion used by real_gen_basic_solver().

anormfloat

If $\text{iterm}=1$ in the previous call to real_gen_basic_setup(), then $anorm$ contains ${\parallel A\parallel }_p$, where $p=1$, $2$ or $\infty$, either supplied or, in the case of $1$ or $\infty$, estimated by real_gen_basic_solver(); otherwise $anorm=0.0$.

sigmaxfloat

If $\text{iterm}=2$ in the previous call to real_gen_basic_setup(), the current estimate of the largest singular value ${\sigma }_1\left(\overline{A}\right)$ of the preconditioned iteration matrix, either when it has been supplied to real_gen_basic_setup() or it has been estimated by real_gen_basic_solver() (see also Notes for real_gen_basic_setup and Parameters for real_gen_basic_setup); otherwise, $sigmax=0.0$ is returned.

Raises

NagValueError

(errno $1$)

real_gen_basic_diag has been called out of sequence.

Notes

real_gen_basic_diag returns information about the solution process. It can be called either during a monitoring step of real_gen_basic_solver() or after real_gen_basic_solver() has completed its tasks. Calling real_gen_basic_diag at any other time will result in an error condition being raised.

For further information you should read the documentation for real_gen_basic_setup() and real_gen_basic_solver().

References

Golub, G H and Van Loan, C F, 1996, Matrix Computations, (3rd Edition), Johns Hopkins University Press, Baltimore

See also

naginterfaces.library.examples.sparse.real_gen_basic_solver_ex.main()