Features

High-level API — XH5F

xh5f_file_object is the primary user-facing type. It coordinates an HDF5 data file and an XDMF metadata file through a single, unified interface. MPI parallelization is handled transparently: each rank writes its own HDF5 file while the master rank assembles the final XDMF descriptor via MPI_GATHERV.

Grid topologies

Block type constant	Description
XH5F_BLOCK_CARTESIAN_UNIFORM	Uniform spacing — described by origin emin(3) and step dxyz(3)
XH5F_BLOCK_CARTESIAN	Variable spacing — described by per-axis node arrays x, y, z
XH5F_BLOCK_CURVILINEAR	General curvilinear mesh — described by full nodes(3,0:ni,0:nj,0:nk) array

Data fields

All field operations are overloaded for ranks and kinds:

Field shape	Leading dimension of nd
Scalar 0D (grid-centered)	— (no nd argument)
Scalar 3D	nd = [ni, nj, nk]
Vector 3D	nd = [3, ni, nj, nk]
Tensor6 3D	nd = [6, ni, nj, nk]
Tensor 3D	nd = [9, ni, nj, nk]
Matrix 3D	nd = [m, ni, nj, nk]

Supported Fortran kinds: R8P, R4P, I8P, I4P, I2P, I1P (via PENF).

Field centering

Constant	Description
XDMF_ATTR_CENTER_CELL	Cell-centered (supported)
XDMF_ATTR_CENTER_GRID	Grid-centered / 0D (supported)
XDMF_ATTR_CENTER_NODE	Node-centered (not yet tested)
XDMF_ATTR_CENTER_EDGE	Edge-centered (not yet tested)
XDMF_ATTR_CENTER_FACE	Face-centered (not yet tested)

DataItem format

Constant	Description
XDMF_DATAITEM_NUMBER_FORMAT_HDF	Data written to HDF5 file, path referenced in XDMF
XDMF_DATAITEM_NUMBER_FORMAT_XML	Data inlined in the XDMF file (suitable for small scalars)

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Low-level API — HDF5

hdf5_file_object provides direct access to HDF5 file and dataset operations.

• Open / close HDF5 files with open_file / close_file
• Open / close simple dataspaces with open_dspace / close_dspace
• Save datasets with save_dataset (overloaded for ranks 0–7 and all PENF kinds)
• Load datasets with load_dataset (same overloads)
• Introspect: does_dataset_exist, get_dataset_dims

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Low-level API — XDMF

xdmf_file_object generates XDMF XML via FoXy.

Grid types

Constant	Description
XDMF_GRID_TYPE_UNIFORM	Single grid
XDMF_GRID_TYPE_COLLECTION	Synchronous collection
XDMF_GRID_TYPE_COLLECTION_ASYNC	Asynchronous collection (MPI use case)
XDMF_GRID_TYPE_TREE	Tree hierarchy
XDMF_GRID_TYPE_SUBSET	Subset of another grid

3-D structured topologies

Constant	Fortran / XDMF name
XDMF_TOPOLOGY_TYPE_3DCORECTMESH	Cartesian uniform
XDMF_TOPOLOGY_TYPE_3DRECTMESH	Cartesian (rectilinear)
XDMF_TOPOLOGY_TYPE_3DSMESH	Curvilinear

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Compiler Support

Compiler	Status
GNU gfortran ≥ 14.2.0	Supported
NVIDIA nvfortran 25.3	Supported
Intel Fortran	Not tested
IBM XL Fortran	Not tested

Design Principles

• Pure Fortran — no C extensions beyond the HDF5 Fortran interface
• OOP — all functionality exposed as type-bound procedures
• KISS — the high-level XH5F API intentionally exposes a minimal surface
• Agnostic kinds — the same method names work for all real/integer precisions
• Free & Open Source — multi-licensed for both FOSS and commercial use