# dfgmres_init

Initializes the solver.

## Syntax

dfgmres_init(n, x, b, RCI_request, ipar, dpar, tmp)

## Description

The routine dfgmres_init iinitializes the solver. After initialization all subsequent invocations of Intel MKL RCI FGMRES routines use the values of all parameters that are returned by dfgmres_init. Advanced users may skip this step and set the values to these parameters directly in the corresponding routines.

### Warning

Users can modify the contents of these arrays after they are passed to the solver routine only if they are sure that the values are correct and consistent. Basic check for correctness and consistency can be done by calling the dfgmres_check routine, but it does not guarantee that the method will work correctly.

## Input Parameters

n

  INTEGER. Contains the size of the problem, and the sizes of arrays x and b.

x

  DOUBLE PRECISION array of size n. Contains the initial approximation to the solution vector. Normally it is equal to 0 or to b.

b

  DOUBLE PRECISION array of size n. Contains the right-hand side vector.

## Output Parameters

RCI_request

  INTEGER. Informs about result of work of the routine.

ipar

  INTEGER array of size 128. Refer to the FGMRES Common Parameters.

dpar

  DOUBLE PRECISION array of size 128. Refer to the FGMRES Common Parameters.

tmp

  DOUBLE PRECISION array of size `((2*ipar(15)+1)*n+ipar(15)*ipar(15)+9)/2 + 1)`. Refer to the FGMRES Common Parameters.

## Return Values

RCI_request= 0

  The routine completes task normally.

RCI_request= -10000

  The routine fails to complete the task.

Parent topic: Iterative Sparse Solvers based on Reverse Communication Interface (RCI ISS)