f_nczarr_compression.f90 File Reference

Deflate+shuffle compression in a local NcZarr dataset (Fortran). More...

Functions/Subroutines
program	f_nczarr_compression
subroutine	handle_err (status)

Detailed Description

Deflate+shuffle compression in a local NcZarr dataset (Fortran).

Fortran equivalent of nczarr_compression.c. Creates a 4x5 temperature array with explicit chunking [2, 5] (y, x) and deflate level 1 + shuffle in a local NcZarr store, verifies compression metadata after reopening, and validates data values.

Learning Objectives:

• Apply deflate compression and shuffle filter from Fortran
• Follow the recommended workflow: set chunks first, then compression
• Query compression metadata after reopen
• Verify that decompression is transparent

Key Concepts:

• Set chunk shape before compression (recommended workflow)
• nf90_def_var_deflate(ncid, varid, shuffle, deflate, deflate_level) enables shuffle and deflate filters
• Compression is transparent: nf90_get_var returns original values
• Same API works for NetCDF-4/HDF5 and NcZarr

Related Examples:

• nczarr_compression.c - C equivalent
• f_nczarr_chunking.f90 - Chunking without compression
• f_nczarr_simple.f90 - Basic NcZarr Fortran example

Compilation:

gfortran -o f_nczarr_compression f_nczarr_compression.f90 -lnetcdff -lnetcdf

Usage:

./f_nczarr_compression
ncdump 'file://f_nczarr_compression.zarr#mode=nczarr'

Expected Output: Creates the directory f_nczarr_compression.zarr containing:

• 2 dimensions: y(4), x(5)
• 1 variable: temperature(y, x) of type NF90_FLOAT, chunked [2, 5], with shuffle + deflate level 1
• Attributes: units="K", long_name="Temperature", _FillValue=-999.0
• A 4x5 temperature data grid stored compressed in 2 chunks

Note

Companion code for "The NetCDF Developer's Handbook: The Authoritative Guide to Writing High-Performance Programs for Scientific Data Management, Second Edition" (https://www.amazon.com/dp/B0H7Q1Z75L)

Author

Edward Hartnett, Intelligent Data Design, Inc.

Date

2026-06-26

Function/Subroutine Documentation

f_nczarr_compression()

program f_nczarr_compression

handle_err()

subroutine f_nczarr_compression::handle_err

(

integer, intent(in)

status

)