# FLASH4.3 API

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## [Functions] source/Grid/Grid_dfsvCompleteSystem

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NAME

```  Grid_dfsvCompleteSystem
```

SYNOPSIS

```  call Grid_dfsvCompleteSystem(
integer(IN), dimension(VARDESC_SIZE) :: baseVarDesc,
integer(IN)  :: ntotVars,
integer(IN)         :: iSrc,
integer(IN)  :: bcTypes(6),
real(IN)     :: bcValues(2,6),
real(IN)     :: dt,
real(IN)     :: chi,
real(IN)     :: scaleFact,
real(IN)     :: theta,
logical(IN)  :: solnIsDelta,
OPTIONAL,integer(IN) :: iFactorC,
OPTIONAL,integer(IN) :: iFactorD,
OPTIONAL,integer(IN) :: pass)
```

DESCRIPTION

```      Completes setting matrix and vector data for a diffusion problem.

The solver advances a generalized diffusion operator of the form

A*(df/dt) + C*f = div(B*grad(f)) + D ,

where
f = f(x,t) is the  Variable to be diffused (x=1D..3D position);

A,B,C,D are optional given scalar factors/terms that may depend
on position; they are either physcially constant in time, or at
least considered time-independent for the purpose of the operation
implemented here (typically by computing their values from the
solution state reached by the previous time step).

Presently it is used to do heat conduction and multigroup diffusion.
```

ARGUMENTS

```   baseVarDesc    : A variable on which the diffusion operation is performed, usually
an extra variable, used to identify the system
ntotVars       : total number or variables to solve for / equations to solve
iFactorA       :| Are factors in the equation with spatial variation.
factorB        :| Factor C,D are optional and are generally used
iFactorC       :| to represent emission/absorption in MGD.
iFactorD       :|
| For this FcB variant of the interface, factorB is passed in
| allocated scratch arrays, i.e., the implementation will have
| to call Grid_ascGetBlkPtr to get at it.
bcTypes        : Presently OUTFLOW, VACUUM is supported, DIRICHLET is untested.
bcValues       : Values of iVar,factorB on boundary (DIRICHLET).
dt             : The time step.
scaleFact      : Factor by which the end solution is scaled (not used).
chi            : useful for constant diffusion problems (not used).
theta          : varies scheme (0-> Explicit, 1-> backward euler, 0.5 -> Crank Nicholson
pass           : Ignored in unsplit solver.
pass=1 order of directional sweep X-Y-Z,
pass=2 order of directional sweep Z-Y-X.
iSrc           : Ignored.
solnIsDelta    : Is the solution only a delta that the caller has to apply to the
temperature, rather than temperature itself (ignored).
```

SIDE EFFECTS

```
```

NOTES

```  This implementation
* supports:
1D, 2D, 3D Cartesian PARAMESH (with local refinement)
1D, 2D, 3D Cartesian in UG (3D untested).
1D Spherical in PARAMESH/UG
1D, 2D Cylindrical in PARAMESH/UG (R-Z)

*  uses HYPRE library to solve AX = B
```

```  Grid_dfsvCreateSystem