f_compression.f90 File Reference

NetCDF-4 compression filters with performance analysis (Fortran) More...

Functions/Subroutines
program	f_compression
logical function	check_zstd_support ()

Detailed Description

NetCDF-4 compression filters with performance analysis (Fortran)

Fortran equivalent of compression.c, exploring NetCDF-4 compression using the Fortran 90 NetCDF API. Tests various compression configurations and measures performance.

Learning Objectives:

• Configure compression with nf90_def_var_deflate() and nf90_def_var_zstandard() in Fortran
• Measure compression performance in Fortran applications
• Select appropriate compression levels for different data
• Set fill values with nf90_def_var_fill() for chunked/compressed variables
• Verify that unwritten chunks return the fill value on read

Fortran Compression Functions:

• nf90_def_var_deflate(ncid, varid, shuffle, deflate, deflate_level)
  • shuffle: 0=off, 1=on; deflate: 0=off, 1=on; deflate_level: 1-9
• nf90_def_var_zstandard(ncid, varid, level)
  • level: 1-22 (higher=better compression, slower)
  • Zstandard is generally faster than zlib and provides better compression ratios. Prefer Zstandard when it is available; level 3 is the best tradeoff.
• zlib is the fallback when Zstandard is unavailable. For almost all real-world data, zlib level 1 is the preferred deflate value. Higher levels yield diminishing returns at much greater CPU cost.

Fortran Fill Value Functions:

• nf90_def_var_fill(ncid, varid, no_fill, fill_value): set fill value (no_fill=0)
• nf90_inq_var_fill(ncid, varid, no_fill, fill_value): query fill value
• In chunked/compressed variables, unwritten chunks return the fill value

Prerequisites:

• f_simple_nc4.f90 - NetCDF-4 format basics
• compression.c - C equivalent

Related Examples:

• compression.c - C equivalent
• f_chunking_performance.f90 - Chunking impacts compression

Compilation:

gfortran -o f_compression f_compression.f90 -lnetcdff -lnetcdf

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

Function/Subroutine Documentation

check_zstd_support()

logical function f_compression::check_zstd_support

(

void

)

f_compression()

program f_compression