The Enzo Hierarchy File - Explanation and Usage

The Enzo Hierarchy file is a representation of the internal memory state of the entire hierarchy of grids. As such, its format -- while somewhat obtuse at first -- reflects that context. Each grid entry has a set number of fields that describe its position in space, as well as the fields that are affiliated with that grid:

Grid = 1
GridRank          = 3
GridDimension     = 38 22 22 
GridStartIndex    = 3 3 3 
GridEndIndex      = 34 18 18 
GridLeftEdge      = 0 0 0 
GridRightEdge     = 1 0.5 0.5 
Time              = 646.75066015177
SubgridsAreStatic = 0
NumberOfBaryonFields = 8
FieldType = 0 1 4 5 6 19 20 21 
BaryonFileName = /scratch/username/RD0005/RedshiftOutput0005.cpu0000
CourantSafetyNumber    = 0.300000
PPMFlatteningParameter = 0
PPMDiffusionParameter  = 0
PPMSteepeningParameter = 0
NumberOfParticles   = 20
ParticleFileName = /scratch/username/RD0005/RedshiftOutput0005.cpu0000
GravityBoundaryType = 0
Pointer: Grid[1]->NextGridThisLevel = 2

The final field, starting with "Pointer", is slightly more complicated and will be discussed below.

Grid = 1

This is the ID of the grid. Enzo grids are indexed-by-one internall.

GridRank = 3

This is the dimensionality of the grid.

GridDimension = 38 22 22

Dimensions, including ghost zones.

GridStartIndex = 3 3 3

The first index of data values owned by this grid.

GridEndIndex = 34 18 18

The final index owned by this grid. The active zones have dimensionality of GridEndIndex - GridStartIndex + 1.

GridLeftEdge = 0 0 0

In code units, between DomainLeftEdge? and DomainRightEdge?, the origin of this grid.

GridRightEdge = 1 0.5 0.5

In code units, between DomainLeftEdge? and DomainRightEdge?, the right-edge of this grid. dx = (GridRightEdge - GridLeftEdge)/(GridEndIndex - GridStartIndex + 1).

Time = 646.75066015177

The current time to which the baryon values in this grid have been evolved.

SubgridsAreStatic = 0

Whether refinement can occur in the subgrids.

NumberOfBaryonFields = 8

The number of data fields associated with this grid.

FieldType = 0 1 4 5 6 19 20 21

The integer identifiers of each field, in order, inside this grid.

BaryonFileName = /scratch/username/RD0005/RedshiftOutput0005.cpu0000

The HDF5 file in which the baryons fields are stored.

CourantSafetyNumber = 0.300000

Courant safety number for this grid (governs timestepping.)

PPMFlatteningParameter = 0

Flattening parameter for this grid (governs PPM hydro.)

PPMDiffusionParameter = 0

Diffusion parameter for this grid (governs PPM hydro.)

PPMSteepeningParameter = 0

Steepening parameter for this grid (governs PPM hydro.)

NumberOfParticles = 20

How many particles are located in this grid at this timestep.

ParticleFileName = /scratch/username/RD0005/RedshiftOutput0005.cpu0000

The HDF5 file in which the baryons fields are stored.

GravityBoundaryType = 0

Boundary type inside gravity solver.