# How to compress HDF5 data?

**URL:** <https://discourse.julialang.org/t/how-to-compress-hdf5-data/2636>\
**Category:** General Usage\
**Tags:** hdf5, data-compression\
**Created:** [March 13, 2017, 10:49am UTC](https://discourse.julialang.org/t/how-to-compress-hdf5-data/2636 "2017-03-13T10:49:51Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![programista](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/programista/32/5372_2.png) [@programista](https://discourse.julialang.org/u/programista)\
**Post date:** [March 13, 2017, 10:49am UTC](https://discourse.julialang.org/t/how-to-compress-hdf5-data/2636/1 "2017-03-13T10:49:51Z")

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How to compress HDF5 data ?

```julia
julia> using HDF5

julia> fid=h5open("file.h5","w")
HDF5 data file: file.h5

julia> close(fid)

julia>

julia> fid = h5open("file.h5","r+")
HDF5 data file: file.h5

julia> write(fid,"A",rand(5,5),"compress")
ERROR: MethodError: no method matching d_create(::HDF5.HDF5File, ::String, ::HDF5.HDF5Datatype, ::HDF5.HDF5Dataspace, ::
String)
Closest candidates are:
  d_create(::Union{HDF5.HDF5File,HDF5.HDF5Group}, ::String, ::HDF5.HDF5Datatype, ::HDF5.HDF5Dataspace, ::String, ::Any,
::Any...) at C:\Users\PC\.julia\v0.5\HDF5\src\plain.jl:828
  d_create(::Union{HDF5.HDF5File,HDF5.HDF5Group}, ::String, ::HDF5.HDF5Datatype, ::HDF5.HDF5Dataspace) at C:\Users\PC\.j
ulia\v0.5\HDF5\src\plain.jl:822
  d_create(::Union{HDF5.HDF5File,HDF5.HDF5Group}, ::String, ::HDF5.HDF5Datatype, ::HDF5.HDF5Dataspace, ::HDF5.HDF5Proper
ties) at C:\Users\PC\.julia\v0.5\HDF5\src\plain.jl:822
  ...
 in _d_create(::HDF5.HDF5File, ::String, ::Array{Float64,2}, ::String, ::Vararg{String,N}) at C:\Users\PC\.julia\v0.5\HD
F5\src\plain.jl:1545
 in d_create(::HDF5.HDF5File, ::String, ::Array{Float64,2}, ::String) at C:\Users\PC\.julia\v0.5\HDF5\src\plain.jl:1552
 in _d_write(::HDF5.HDF5File, ::String, ::Array{Float64,2}, ::String, ::Vararg{String,N}) at C:\Users\PC\.julia\v0.5\HDF
5\src\plain.jl:1578
 in write(::HDF5.HDF5File, ::String, ::Array{Float64,2}, ::String) at C:\Users\PC\.julia\v0.5\HDF5\src\plain.jl:1614

julia> write(fid,"A",rand(5,5),'compress')
ERROR: syntax: invalid character literal

```

Paul

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**Author:** ![tamasgal](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamasgal/32/27946_2.png) [@tamasgal](https://discourse.julialang.org/u/tamasgal)\
**Post date:** [March 13, 2017, 12:48pm UTC](https://discourse.julialang.org/t/how-to-compress-hdf5-data/2636/2 "2017-03-13T12:48:37Z")

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You can’t use the `write` function to define the compression, you need to create chunks.

Have a look at the docs of HDF5.jl here: [https://github.com/JuliaIO/HDF5.jl/blob/master/doc/hdf5.md](https://github.com/JuliaIO/HDF5.jl/blob/master/doc/hdf5.md)

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**Author:** ![jwu](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jwu/32/3775_2.png) [@jwu](https://discourse.julialang.org/u/jwu)\
**Post date:** [March 13, 2017, 2:46pm UTC](https://discourse.julialang.org/t/how-to-compress-hdf5-data/2636/3 "2017-03-13T14:46:37Z")

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HDF5 works pretty good with Blosc.jl  
You can use multithreaded compression using Blosc.jl