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Subsections

4 Infrastructure: Fields and Grids

15 Overview of Infrastructure Data Handling

The ESMF infrastructure data classes are part of the framework's hierarchy of structures for handling Earth system model data and metadata on parallel platforms. The hierarchy is in complexity; the simplest data class in the infrastructure represents a distributed data array and the most complex data class represents a bundle of physical fields that are discretized on the same grid. However, the current C API does not support bundled data structures yet. Array and Field are the two data classes offered by the ESMF C language binding. Data class methods are called both from user-written code and from other classes internal to the framework.

Data classes are distributed over DEs, or Decomposition Elements. A DE represents a piece of a decomposition. A DELayout is a collection of DEs with some associated connectivity that describes a specific distribution. For example, the distribution of a grid divided into four segments in the x-dimension would be expressed in ESMF as a DELayout with four DEs lying along an x-axis. This abstract concept enables a data decomposition to be defined in terms of threads, MPI processes, virtual decomposition elements, or combinations of these without changes to user code. This is a primary strategy for ensuring optimal performance and portability for codes using the ESMF for communications.

ESMF data classes are useful because they provide a standard, convenient way for developers to collect together information related to model or observational data. The information assembled in a data class includes a data pointer, a set of attributes (e.g. units, although attributes can also be user-defined), and a description of an associated grid. The same set of information within an ESMF data object can be used by the framework to arrange intercomponent data transfers, to perform I/O, for communications such as gathers and scatters, for simplification of interfaces within user code, for debugging, and for other functions. This unifies and organizes codes overall so that the user need not define different representations of metadata for the same field for I/O and for component coupling.

Since it is critical that users be able to introduce ESMF into their codes easily and incrementally, ESMF data classes can be created based on native Fortran pointers. Likewise, there are methods for retrieving native Fortran pointers from within ESMF data objects. This allows the user to perform allocations using ESMF, and to retrieve Fortran arrays later for optimized model calculations. The ESMF data classes do not have associated differential operators or other mathematical methods.

For flexibility, it is not necessary to build an ESMF data object all at once. For example, it's possible to create a field but to defer allocation of the associated field data until a later time.


Key Features
Hierarchy of data structures designed specifically for the Earth system domain and high performance, parallel computing.
Multi-use ESMF structures simplify user code overall.
Data objects support incremental construction and deferred allocation.
Native Fortran arrays can be associated with or retrieved from ESMF data objects, for ease of adoption, convenience, and performance.

15.1 Infrastructure Data Classes

The main classes that are used for model and observational data manipulation are as follows:

15.2 Design and Implementation Notes

  1. In communication methods such as Regrid, Redist, Scatter, etc. the Field code cascades down through the Array code, so that the actual implementation exist in only one place in the source.

16 Field Class

16.1 Description

An ESMF Field represents a physical field, such as temperature. The motivation for including Fields in ESMF is that bundles of Fields are the entities that are normally exchanged when coupling Components.

The ESMF Field class contains distributed and discretized field data, a reference to its associated grid, and metadata. The Field class stores the grid staggering for that physical field. This is the relationship of how the data array of a field maps onto a grid (e.g. one item per cell located at the cell center, one item per cell located at the NW corner, one item per cell vertex, etc.). This means that different Fields which are on the same underlying ESMF Grid but have different staggerings can share the same Grid object without needing to replicate it multiple times.

Fields can be added to States for use in inter-Component data communications.

Field communication capabilities include: data redistribution, regridding, scatter, gather, sparse-matrix multiplication, and halo update. These are discussed in more detail in the documentation for the specific method calls. ESMF does not currently support vector fields, so the components of a vector field must be stored as separate Field objects.

A Field serves as an annotator of data, since it carries a description of the grid it is associated with and metadata such as name and units. Fields can be used in this capacity alone, as convenient, descriptive containers into which arrays can be placed and retrieved. However, for most codes the primary use of Fields is in the context of import and export States, which are the objects that carry coupling information between Components. Fields enable data to be self-describing, and a State holding ESMF Fields contains data in a standard format that can be queried and manipulated.

The sections below go into more detail about Field usage.

16.1.1 Field create and destroy

Fields can be created and destroyed at any time during application execution. However, these Field methods require some time to complete. We do not recommend that the user create or destroy Fields inside performance-critical computational loops.

All versions of the ESMC_FieldCreate() routines require a Mesh object as input. The Mesh contains the information needed to know which Decomposition Elements (DEs) are participating in the processing of this Field, and which subsets of the data are local to a particular DE.

The details of how the create process happens depends on which of the variants of the ESMC_FieldCreate() call is used.

When finished with an ESMC_Field, the ESMC_FieldDestroy method removes it. However, the objects inside the ESMC_Field created externally should be destroyed separately, since objects can be added to more than one ESMC_Field. For example, the same ESMF_Mesh can be referenced by multiple ESMC_Fields. In this case the internal Mesh is not deleted by the ESMC_FieldDestroy call.

16.2 Class API

16.2.1 ESMC_FieldCreate - Create a Field


INTERFACE:

 ESMC_Field ESMC_FieldCreate(
   ESMC_Mesh mesh,                           // in
   ESMC_ArraySpec arrayspec,                 // in
   ESMC_InterfaceInt gridToFieldMap,         // in
   ESMC_InterfaceInt ungriddedLBound,        // in
   ESMC_InterfaceInt ungriddedUBound,        // in
   const char *name,                         // in
   int *rc                                   // out
 );
RETURN VALUE:
    Newly created ESMC_Field object.
DESCRIPTION:

Creates a ESMC_Field object.

The arguments are:

mesh
A ESMC_Mesh object.
arrayspec
A ESMC_ArraySpec object describing data type and kind specification.
gridToFieldMap
List with number of elements equal to the grid's dimCount. The list elements map each dimension of the grid to a dimension in the field by specifying the appropriate field dimension index. The default is to map all of the grid's dimensions against the lowest dimensions of the field in sequence, i.e. gridToFieldMap = (/1,2,3,.../). The values of all gridToFieldMap entries must be greater than or equal to one and smaller than or equal to the field rank. It is erroneous to specify the same gridToFieldMap entry multiple times. The total ungridded dimensions in the field are the total field dimensions less the dimensions in the grid. Ungridded dimensions must be in the same order they are stored in the field. If the Field dimCount is less than the Mesh dimCount then the default gridToFieldMap will contain zeros for the rightmost entries. A zero entry in the gridToFieldMap indicates that the particular Mesh dimension will be replicating the Field across the DEs along this direction.
ungriddedLBound
Lower bounds of the ungridded dimensions of the field. The number of elements in the ungriddedLBound is equal to the number of ungridded dimensions in the field. All ungridded dimensions of the field are also undistributed. When field dimension count is greater than grid dimension count, both ungriddedLBound and ungriddedUBound must be specified. When both are specified the values are checked for consistency. Note that the the ordering of these ungridded dimensions is the same as their order in the field.
ungriddedUBound
Upper bounds of the ungridded dimensions of the field. The number of elements in the ungriddedUBound is equal to the number of ungridded dimensions in the field. All ungridded dimensions of the field are also undistributed. When field dimension count is greater than grid dimension count, both ungriddedLBound and ungriddedUBound must be specified. When both are specified the values are checked for consistency. Note that the the ordering of these ungridded dimensions is the same as their order in the field.
[name]
The name for the newly created field. If not specified, i.e. NULL, a default unique name will be generated: "FieldNNN" where NNN is a unique sequence number from 001 to 999.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

16.2.2 ESMC_FieldDestroy - Destroy a Field


INTERFACE:

 int ESMC_FieldDestroy(
   ESMC_Field *field     // inout
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Releases all resources associated with this ESMC_Field. Return code; equals ESMF_SUCCESS if there are no errors.

The arguments are:

field
Destroy contents of this ESMC_Field.

16.2.3 ESMC_FieldGetArray - Get the internal Array stored in the Field


INTERFACE:

 ESMC_Array ESMC_FieldGetArray(
   ESMC_Field field,     // in
   int *rc               // out
 );
RETURN VALUE:
    The ESMC_Array object stored in the ESMC_Field.
DESCRIPTION:

Get the internal Array stored in the ESMC_Field.

The arguments are:

field
Get the internal Array stored in this ESMC_Field.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

16.2.4 ESMC_FieldGetMesh - Get the internal Mesh stored in the Field


INTERFACE:

 ESMC_Mesh ESMC_FieldGetMesh(
   ESMC_Field field,     // in
   int *rc               // out
 );
RETURN VALUE:
    The ESMC_Mesh object stored in the ESMC_Field.
DESCRIPTION:

Get the internal Mesh stored in the ESMC_Field.

The arguments are:

field
Get the internal Mesh stored in this ESMC_Field.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

16.2.5 ESMC_FieldGetPtr - Get the internal Fortran data pointer stored in the Field


INTERFACE:

 void *ESMC_FieldGetPtr(
   ESMC_Field field,     // in
   int localDe,          // in
   int *rc               // out
 );
RETURN VALUE:
    The Fortran data pointer stored in the ESMC_Field.
DESCRIPTION:

Get the internal Fortran data pointer stored in the ESMC_Field.

The arguments are:

field
Get the internal Fortran data pointer stored in this ESMC_Field.
localDe
Local DE for which information is requested. [0,..,localDeCount-1].
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

16.2.6 ESMC_FieldPrint - Print the internal information of a Field


INTERFACE:

 int ESMC_FieldPrint(
   ESMC_Field field      // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Print the internal information within this ESMC_Field. Return code; equals ESMF_SUCCESS if there are no errors.

The arguments are:

field
Print contents of this ESMC_Field.

17 Array Class

17.1 Description

The Array class is an alternative to the Field class for representing distributed, structured data. Unlike Fields, which are built to carry grid coordinate information, Arrays can only carry information about the indices associated with grid cells. Since they do not have coordinate information, Arrays cannot be used to calculate interpolation weights. However, if the user can supply interpolation weights, the Array sparse matrix multiply operation can be used to apply the weights and transfer data to the new grid. Arrays can also perform redistribution, scatter, and gather communication operations.

Like Fields, Arrays can be added to a State and used in inter-Component data communications.

From a technical standpoint, the ESMF Array class is an index space based, distributed data storage class. It provides DE-local memory allocations within DE-centric index regions and defines the relationship to the index space described by the ESMF DistGrid. The Array class offers common communication patterns within the index space formalism.

17.2 Class API

17.2.1 ESMC_ArrayCreate - Create an Array


INTERFACE:

 ESMC_Array ESMC_ArrayCreate(
   ESMC_ArraySpec arrayspec,   // in
   ESMC_DistGrid distgrid,     // in
   const char* name,           // in
   int *rc                     // out
 );
RETURN VALUE:
    Newly created ESMC_Array object.
DESCRIPTION:

Create an ESMC_Array object.

The arguments are:

arrayspec
ESMC_ArraySpec object containing the type/kind/rank information.
distgrid
ESMC_DistGrid object that describes how the Array is decomposed and distributed over DEs. The dimCount of distgrid must be smaller or equal to the rank specified in arrayspec, otherwise a runtime ESMF error will be raised.
[name]
The name for the Array object. If not specified, i.e. NULL, a default unique name will be generated: "ArrayNNN" where NNN is a unique sequence number from 001 to 999.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

17.2.2 ESMC_ArrayDestroy - Destroy an Array


INTERFACE:

 int ESMC_ArrayDestroy(
   ESMC_Array *array           // inout
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Destroy an ESMC_Array object.

The arguments are:

array
ESMC_Array object to be destroyed.

17.2.3 ESMC_ArrayGetName - Get the name of an Array


INTERFACE:

 const char *ESMC_ArrayGetName(
   ESMC_Array array,           // in
   int *rc                     // out
 );
RETURN VALUE:
    Pointer to the Array name string.
DESCRIPTION:

Get the name of the specified ESMC_Array object.

The arguments are:

array
ESMC_Array object to be queried.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

17.2.4 ESMC_ArrayGetPtr - Get pointer to Array data.


INTERFACE:

 void *ESMC_ArrayGetPtr(
   ESMC_Array array,           // in
   int localDe,                // in
   int *rc                     // out
 );
RETURN VALUE:
    Pointer to the Array data.
DESCRIPTION:

Get pointer to the data of the specified ESMC_Array object.

The arguments are:

array
ESMC_Array object to be queried.
localDe
Local De for which to data pointer is queried.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

17.2.5 ESMC_ArrayPrint - Print an Array


INTERFACE:

 int ESMC_ArrayPrint(
   ESMC_Array array            // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Print internal information of the specified ESMC_Array object.

The arguments are:

array
ESMC_Array object to be printed.

18 ArraySpec Class

18.1 Description

An ArraySpec is a very simple class that contains type, kind, and rank information about an Array. This information is stored in two parameters. TypeKind describes the data type of the elements in the Array and their precision. Rank is the number of dimensions in the Array.

The only methods that are associated with the ArraySpec class are those that allow you to set and retrieve this information.

18.2 Class API

18.2.1 ESMC_ArraySpecGet - Get values from an ArraySpec


INTERFACE:

 int ESMC_ArraySpecGet(
   ESMC_ArraySpec arrayspec,         // inout
   int *rank,                        // in
   enum ESMC_TypeKind *typekind      // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Returns information about the contents of an ESMC_ArraySpec.

The arguments are:

arrayspec
The ESMC_ArraySpec to query.
rank
Array rank (dimensionality - 1D, 2D, etc). Maximum allowed is 7D.
typekind
Array typekind. See section ?? for valid values.

18.2.2 ESMC_ArraySpecSet - Set values for an ArraySpec


INTERFACE:

 int ESMC_ArraySpecSet(
   ESMC_ArraySpec *arrayspec,         // inout 
   int rank,                          // in
   enum ESMC_TypeKind typekind        // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Set an Array specification - typekind, and rank.

The arguments are:

arrayspec
The ESMC_ArraySpec to set.
rank
Array rank (dimensionality - 1D, 2D, etc). Maximum allowed is 7D.
typekind
Array typekind. See section ?? for valid values.

19 Mesh Class

19.1 Description

Unstructured grids are commonly used in the computational solution of Partial Differential equations. These are especially useful for problems that involve complex geometry, where using the less flexible structured grids can result in grid representation of regions where no computation is needed. Finite element and finite volume methods map naturally to unstructured grids and are used commonly in hydrology, ocean modeling, and many other applications.

In order to provide support for application codes using unstructured grids, the ESMF library provides a class for representing unstructured grids called the Mesh. Fields can be created on a Mesh to hold data. In Fortran, Fields created on a Mesh can also be used as either the source or destination or both of an interpolaton (i.e. an ESMF_FieldRegridStore() call). This capability is currently not supported with the C interface, however, if the C Field is passed via a State to a component written in Fortran then the regridding can be performed there. The rest of this section describes the Mesh class and how to create and use them in ESMF.

19.1.1 Mesh Representation in ESMF

A Mesh in ESMF is described in terms of nodes and elements. A node is a point in space which represents where the coordinate information in a Mesh is located. An element is a higher dimensional shape constructed of nodes. Elements give a Mesh its shape and define the relationship of the nodes to one another. Field data may be located on a Mesh's nodes.

19.1.2 Supported Meshes

The range of Meshes supported by ESMF are defined by several factors: dimension, element types, and distribution.

ESMF currently only supports Meshes whose number of coordinate dimensions (spatial dimension) is 2 or 3. The dimension of the elements in a Mesh (parametric dimension) must be less than or equal to the spatial dimension, but also must be either 2 or 3. This means that an ESMF mesh may be either 2D elements in 2D space, 3D elements in 3D space, or a manifold constructed of 2D elements embedded in 3D space.

ESMF currently supports two types of elements for each Mesh parametric dimension. For a parametric dimension of 2 the supported element types are triangles or quadralaterals. For a parametric dimension of 3 the supported element types are tetrahedrons and hexahedrons. See Section 19.2.1 for diagrams of these. The Mesh supports any combination of element types within a particular dimension, but types from different dimensions may not be mixed, for example, a Mesh cannot be constructed of both quadralaterals and tetrahedra.

ESMF currently only supports distributions where every node on a PET must be a part of an element on that PET. In other words, there must not be nodes without an element on a PET.

19.2 Constants


19.2.1 ESMC_MESHELEMTYPE

DESCRIPTION:
An ESMF Mesh can be constructed from a combination of different elements. The type of elements that can be used in a Mesh depends on the Mesh's parameteric dimension, which is set during Mesh creation. The following are the valid Mesh element types for each valid Mesh parametric dimension (2D or 3D) .


                     3                          4 ---------- 3
                    / \                         |            |  
                   /   \                        |            |
                  /     \                       |            |
                 /       \                      |            |
                /         \                     |            |
               1 --------- 2                    1 ---------- 2

           ESMC_MESHELEMTYPE_TRI            ESMC_MESHELEMTYPE_QUAD

2D element types (numbers are the order for elementConn during 
                  Mesh create)

For a Mesh with parametric dimension of 2 the valid element types (illustrated above) are:

Element Type Number of Nodes Description
ESMC_MESHELEMTYPE_TRI 3 A triangle
ESMC_MESHELEMTYPE_QUAD 4 A quadrilateral (e.g. a rectangle)



                                            
                 3                               8---------------7
                /|\                             /|              /|
               / | \                           / |             / |
              /  |  \                         /  |            /  |
             /   |   \                       /   |           /   |
            /    |    \                     5---------------6    |
           4-----|-----2                    |    |          |    |
            \    |    /                     |    4----------|----3
             \   |   /                      |   /           |   /
              \  |  /                       |  /            |  /
               \ | /                        | /             | /
                \|/                         |/              |/
                 1                          1---------------2

       ESMC_MESHELEMTYPE_TETRA             ESMC_MESHELEMTYPE_HEX  

3D element types (numbers are the order for elementConn during 
                  Mesh create)

For a Mesh with parametric dimension of 3 the valid element types (illustrated above) are:

Element Type Number of Nodes Description
ESMC_MESHELEMTYPE_TETRA 4 A tetrahedron (CAN'T BE USED IN REGRID)
ESMC_MESHELEMTYPE_HEX 8 A hexahedron (e.g. a cube)

19.3 Class API


19.3.1 ESMC_MeshAddElements - Add elements to a Mesh


INTERFACE:

 int ESMC_MeshAddElements(
   ESMC_Mesh mesh,           // inout 
   int  elementCount,        // in
   int *elementIds,          // in
   int *elementTypes,        // in
   int *elementConn          // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

This call is the third and last part of the three part mesh create sequence and should be called after the mesh is created with ESMF_MeshCreate() (19.3.3) and after the nodes are added with ESMF_MeshAddNodes() (19.3.2). This call adds the elements to the mesh and finalizes the create. After this call the Mesh is usable, for example a Field may be built on the created Mesh object and this Field may be used in a ESMF_FieldRegridStore() call.

The parameters to this call elementIds, elementTypes, and elementConn describe the elements to be created. The description for a particular element lies at the same index location in elementIds and elementTypes. Each entry in elementConn consists of the list of nodes used to create that element, so the connections for element $e$ in the elementIds array will start at $number\_of\_nodes\_in\_element(1) + number\_of\_nodes\_in\_element(2) +
\cdots + number\_of\_nodes\_in\_element(e-1) + 1$ in elementConn.

mesh
Mesh object.
elementCount
The number of elements on this PET.
elementIds
An array containing the global ids of the elements to be created on this PET. This input consists of a 1D array of size elementCount.
elementTypes
An array containing the types of the elements to be created on this PET. The types used must be appropriate for the parametric dimension of the Mesh. Please see Section [*] for the list of options. This input consists of a 1D array of size elementCount.
elementConn
An array containing the indexes of the sets of nodes to be connected together to form the elements to be created on this PET. The entries in this list are NOT node global ids, but rather each entry is a local index (1 based) into the list of nodes which were created on this PET by the previous ESMC_MeshAddNodes() call. In other words, an entry of 1 indicates that this element contains the node described by nodeIds(1), nodeCoords(1), etc. passed into the ESMC_MeshAddNodes() call on this PET. It is also important to note that the order of the nodes in an element connectivity list matters. Please see Section [*] for diagrams illustrating the correct order of nodes in a element. This input consists of a 1D array with a total size equal to the sum of the number of nodes in each element on this PET. The number of nodes in each element is implied by its element type in elementTypes. The nodes for each element are in sequence in this array (e.g. the nodes for element 1 are elementConn(1), elementConn(2), etc.).


19.3.2 ESMC_MeshAddNodes - Add nodes to a Mesh


INTERFACE:

 int ESMC_MeshAddNodes(
   ESMC_Mesh mesh,          // inout
   int nodeCount,           // in
   int *nodeIds,            // in
   double *nodeCoords,      // in
   int *nodeOwners          // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

This call is the second part of the three part mesh create sequence and should be called after the mesh's dimensions are set using ESMC_MeshCreate(). This call adds the nodes to the mesh. The next step is to call ESMC_MeshAddElements() (19.3.3).

The parameters to this call nodeIds, nodeCoords, and nodeOwners describe the nodes to be created on this PET. The description for a particular node lies at the same index location in nodeIds and nodeOwners. Each entry in nodeCoords consists of spatial dimension coordinates, so the coordinates for node $n$ in the nodeIds array will start at $(n-1)*spatialDim+1$.

mesh
Mesh object.
nodeCount
The number of nodes on this PET.
nodeIds
An array containing the global ids of the nodes to be created on this PET. This input consists of a 1D array the size of the number of nodes on this PET (i.e. nodeCount).
nodeCoords
An array containing the physical coordinates of the nodes to be created on this PET. The coordinates in this array are ordered so that the coordinates for a node lie in sequence in memory. (e.g. for a Mesh with spatial dimension 2, the coordinates for node 1 are in nodeCoords(0) and nodeCoords(1), the coordinates for node 2 are in nodeCoords(2) and nodeCoords(3), etc.). This input consists of a 1D array the size of nodeCount times the Mesh's spatial dimension (spatialDim).
nodeOwners
An array containing the PETs that own the nodes to be created on this PET. If the node is shared with another PET, the value may be a PET other than the current one. Only nodes owned by this PET will have PET local entries in a Field created on the Mesh. This input consists of a 1D array the size of the number of nodes on this PET (i.e. nodeCount).


19.3.3 ESMC_MeshCreate - Create a Mesh as a 3 step process


INTERFACE:

 ESMC_Mesh ESMC_MeshCreate(
   int parametricDim,         // in
   int spatialDim,            // in
   int *rc                    // out
 );
RETURN VALUE:
    type(ESMC_Mesh)         :: ESMC_MeshCreate
DESCRIPTION:

This call is the first part of the three part mesh create sequence. This call sets the dimension of the elements in the mesh (parametricDim) and the number of coordinate dimensions in the mesh (spatialDim). The next step is to call ESMC_MeshAddNodes() (19.3.2) to add the nodes and then ESMC_MeshAddElements() (19.3.1) to add the elements and finalize the mesh.

The arguments are:

parametricDim
Dimension of the topology of the Mesh. (E.g. a mesh constructed of squares would have a parametric dimension of 2, whereas a Mesh constructed of cubes would have one of 3.)
spatialDim
The number of coordinate dimensions needed to describe the locations of the nodes making up the Mesh. For a manifold, the spatial dimesion can be larger than the parametric dim (e.g. the 2D surface of a sphere in 3D space), but it can't be smaller.
rc
Return code; equals ESMF_SUCCESS if there are no errors.

19.3.4 ESMC_MeshDestroy - Destroy a Mesh


INTERFACE:

 int ESMC_MeshDestroy(
   ESMC_Mesh *mesh             // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Destroy the Mesh. This call removes all internal memory associated with mesh. After this call mesh will no longer be usable.

The arguments are:

mesh
Mesh object whose memory is to be freed.

19.3.5 ESMC_MeshFreeMemory - Remove a Mesh and its memory


INTERFACE:

 int ESMC_MeshFreeMemory(
   ESMC_Mesh mesh            // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

This call removes the portions of mesh which contain connection and coordinate information. After this call, Fields build on mesh will no longer be usable as part of an ESMF_FieldRegridStore() operation. However, after this call Fields built on mesh can still be used in an ESMF_FieldRegrid() operation if the routehandle was generated beforehand. New Fields may also be built on mesh after this call.

The arguments are:

mesh
Mesh object whose memory is to be freed.

19.3.6 ESMC_MeshGetLocalElementCount - Get the number of elements in a Mesh owned by the current PET


INTERFACE:

 int ESMC_MeshGetLocalElementCount(
   ESMC_Mesh mesh,           // in
   int *elementCount         // out
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Query the number of elements in a mesh owned by the local PET. The arguments are:

mesh
The mesh
elementCount
The number of elements on this PET.

19.3.7 ESMC_MeshGetLocalNodeCount - Get the number of nodes in a Mesh owned by the current PET


INTERFACE:

 int ESMC_MeshGetLocalNodeCount(
   ESMC_Mesh mesh,          // in
   int *nodeCount           // out
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Query the number of nodes in a mesh owned by the local PET. The arguments are:

mesh
The mesh
nodeCount
The number of nodes on this PET.

20 DistGrid Class

20.1 Description

The ESMF DistGrid class sits on top of the DELayout class (not currently directly accessible through the ESMF C API) and holds domain information in index space. A DistGrid object captures the index space topology and describes its decomposition in terms of DEs. Combined with DELayout and VM the DistGrid defines the data distribution of a domain decomposition across the computational resources of an ESMF Component.

The global domain is defined as the union or ``tilework'' of logically rectangular (LR) sub-domains or tiles. The DistGrid create methods allow the specification of such a tilework global domain and its decomposition into exclusive, DE-local LR regions according to various degrees of user specified constraints. Complex index space topologies can be constructed by specifying connection relationships between tiles during creation.

The DistGrid class holds domain information for all DEs. Each DE is associated with a local LR region. No overlap of the regions is allowed. The DistGrid offers query methods that allow DE-local topology information to be extracted, e.g. for the construction of halos by higher classes.

A DistGrid object only contains decomposable dimensions. The minimum rank for a DistGrid object is 1. A maximum rank does not exist for DistGrid objects, however, ranks greater than 7 may lead to difficulties with respect to the Fortran API of higher classes based on DistGrid. The rank of a DELayout object contained within a DistGrid object must be equal to the DistGrid rank. Higher class objects that use the DistGrid, such as an Array object, may be of different rank than the associated DistGrid object. The higher class object will hold the mapping information between its dimensions and the DistGrid dimensions.

20.2 Class API

20.2.1 ESMC_DistGridCreate - Create a DistGrid


INTERFACE:

 ESMC_DistGrid ESMC_DistGridCreate(
   ESMC_InterfaceInt minIndexInterfaceArg,   // in
   ESMC_InterfaceInt maxIndexInterfaceArg,   // in
   int *rc                                   // out
 );
RETURN VALUE:
    Newly created ESMC_DistGrid object.
DESCRIPTION:

Create an ESMC_DistGrid from a single logically rectangular (LR) tile with default decomposition. The default decomposition is deCount $ \times 1 \times ... \times 1$, where deCount is the number of DEs in a default DELayout, equal to petCount. This means that the default decomposition will be into as many DEs as there are PETs, with 1 DE per PET.

The arguments are:

minIndex
Global coordinate tuple of the lower corner of the tile.
maxIndex
Global coordinate tuple of the upper corner of the tile.
[rc]
Return code; equals ESMF_SUCCESS if there are no errors.

20.2.2 ESMC_DistGridDestroy - Destroy a DistGrid


INTERFACE:

 int ESMC_DistGridDestroy(
   ESMC_DistGrid *distgrid         // inout
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Destroy an ESMC_DistGrid object.

The arguments are:

distgrid
ESMC_DistGrid object to be destroyed.

20.2.3 ESMC_DistGridPrint - Print a DistGrid


INTERFACE:

 int ESMC_DistGridPrint(
   ESMC_DistGrid distgrid          // in
 );
RETURN VALUE:
    Return code; equals ESMF_SUCCESS if there are no errors.
DESCRIPTION:

Print internal information of the specified ESMC_DistGrid object.

The arguments are:

distgrid
ESMC_DistGrid object to be destroyed.


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