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Save/Convert/Load MERA-Files

The RAMSES simulation data can be stored and accessed from files in the JLD2 file format.

using Mera

Load the Data From Ramses

info = getinfo(300,  "/Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10");
gas  = gethydro(info, verbose=false, show_progress=false); 
part = getparticles(info, verbose=false, show_progress=false); 
grav = getgravity(info, verbose=false, show_progress=false); 
# the same applies for clump-data...
[Mera]: 2025-06-21T22:36:43.204

Code: RAMSES
output [300] summary:
mtime: 2023-04-09T05:34:09
ctime: 2025-06-21T18:31:24.020
=======================================================
simulation time: 445.89 [Myr]
boxlen: 48.0 [kpc]
ncpu: 640
ndim: 3
-------------------------------------------------------
amr:           true
level(s): 6 - 10 --> cellsize(s): 750.0 [pc] - 46.88 [pc]
-------------------------------------------------------
hydro:         true
hydro-variables:  7  --> (:rho, :vx, :vy, :vz, :p, :var6, :var7)
hydro-descriptor: (:density, :velocity_x, :velocity_y, :velocity_z, :pressure, :scalar_00, :scalar_01)
γ: 1.6667
-------------------------------------------------------
gravity:       true
gravity-variables: (:epot, :ax, :ay, :az)
-------------------------------------------------------
particles:     true
- Nstars:   5.445150e+05 
particle-variables: 7  --> (:vx, :vy, :vz, :mass, :family, :tag, :birth)
particle-descriptor: (:position_x, :position_y, :position_z, :velocity_x, :velocity_y, :velocity_z, :mass, :identity, :levelp, :family, :tag, :birth_time)
-------------------------------------------------------
rt:            false
clumps:           false
-------------------------------------------------------
namelist-file: ("&COOLING_PARAMS", "&SF_PARAMS", "&AMR_PARAMS", "&BOUNDARY_PARAMS", "&OUTPUT_PARAMS", "&POISSON_PARAMS", "&RUN_PARAMS", "&FEEDBACK_PARAMS", "&HYDRO_PARAMS", "&INIT_PARAMS", "&REFINE_PARAMS")
-------------------------------------------------------
timer-file:       true
compilation-file: false
makefile:         true
patchfile:        true
=======================================================

Store the Data Into JLD2 Files

The running number is taken from the original RAMSES outputs.

savedata(gas, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/");
[Mera]: 2025-06-21T22:39:38.006


Not existing file: output_00300.jld2
Directory: /Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10
-----------------------------------
merafile_version: 1.0  -  Simulation code: RAMSES
-----------------------------------
DataType: hydro  -  Data variables: (:level, :cx, :cy, :cz, :rho, :vx, :vy, :vz, :p, :var6, :var7)
-----------------------------------
I/O mode: nothing  -  Compression: nothing
-----------------------------------
-----------------------------------
Memory size: 2.321 GB (uncompressed)
-----------------------------------

<div class="alert alert-block alert-info"> <b>NOTE</b> The hydro data was not written into the file to prevent overwriting existing files.

The following argument is mandatory: fmode=:write </div>

savedata(gas, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", fmode=:write);
[Mera]: 2025-06-21T22:39:38.861


Create file: output_00300.jld2
Directory: /Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10
-----------------------------------
merafile_version: 1.0  -  Simulation code: RAMSES
-----------------------------------
DataType: hydro  -  Data variables: (:level, :cx, :cy, :cz, :rho, :vx, :vy, :vz, :p, :var6, :var7)
-----------------------------------
I/O mode: write  -  Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0xc0, 0xa4, 0xfe, 0x2a, 0x01, 0x00, 0x00, 0x00, 0xc0, 0x26, 0x24, 0x82, 0x01, 0x00, 0x00, 0x00, 0xf0, 0xe3, 0xae], false)
-----------------------------------
CodecLz4  0.4.6
JLD2  0.5.13
CodecBzip2  0.8.5
Mera  1.4.5
CodecZlib  0.7.8
-----------------------------------
Memory size: 2.321 GB (uncompressed)
Total file size: 1.276 GB
-----------------------------------

Add/Append further datatypes:

savedata(part, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", fmode=:append);
savedata(grav, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", fmode=:append);
[Mera]: 2025-06-21T22:40:33.359


Create file: output_00300.jld2
Directory: /Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10
-----------------------------------
merafile_version: 1.0  -  Simulation code: RAMSES
-----------------------------------
DataType: particles  -  Data variables: (:level, :x, :y, :z, :id, :family, :tag, :vx, :vy, :vz, :mass, :birth)
-----------------------------------
I/O mode: append  -  Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0xe0, 0x20, 0x71, 0x29, 0x01, 0x00, 0x00, 0x00, 0x70, 0x44, 0xc6, 0x2c, 0x01, 0x00, 0x00, 0x00, 0x90, 0xe3, 0x2a], false)
-----------------------------------
CodecLz4  0.4.6
JLD2  0.5.13
CodecBzip2  0.8.5
Mera  1.4.5
CodecZlib  0.7.8
-----------------------------------
Memory size: 38.449 MB (uncompressed)
Total file size: 1.306 GB
-----------------------------------

[Mera]: 2025-06-21T22:40:35.362


Create file: output_00300.jld2
Directory: /Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10
-----------------------------------
merafile_version: 1.0  -  Simulation code: RAMSES
-----------------------------------
DataType: gravity  -  Data variables: (:level, :cx, :cy, :cz, :epot, :ax, :ay, :az)
-----------------------------------
I/O mode: append  -  Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], false)
-----------------------------------
CodecLz4  0.4.6
JLD2  0.5.13
CodecBzip2  0.8.5
Mera  1.4.5
CodecZlib  0.7.8
-----------------------------------
Memory size: 1.688 GB (uncompressed)
Total file size: 2.159 GB
-----------------------------------

<div class="alert alert-block alert-info"> <b>NOTE</b> It is not possible to exchange stored data; only writing into a new file or appending is supported. </div>

Overview of Stored Data

vd = viewdata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/")
[Mera]: 2025-06-21T22:40:39.995

Mera-file output_00300.jld2 contains:

Datatype: particles
merafile_version: 1.0
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0xe0, 0x20, 0x71, 0x29, 0x01, 0x00, 0x00, 0x00, 0x70, 0x44, 0xc6, 0x2c, 0x01, 0x00, 0x00, 0x00, 0x90, 0xe3, 0x2a], false)
CodecZlib: VersionNumber[v"0.7.8"]
merafile_version: 1.0
JLD2: VersionNumber[v"0.5.13"]
CodecBzip2: VersionNumber[v"0.8.5"]
JLD2compatible_versions: (lower = v"0.1.0", upper = v"0.3.0")
CodecLz4: VersionNumber[v"0.4.6"]
Mera: VersionNumber[v"1.4.5"]
-------------------------
Memory: 38.44882392883301 MB (uncompressed)


Datatype: gravity
merafile_version: 1.0
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], false)
CodecZlib: VersionNumber[v"0.7.8"]
merafile_version: 1.0
JLD2: VersionNumber[v"0.5.13"]
CodecBzip2: VersionNumber[v"0.8.5"]
JLD2compatible_versions: (lower = v"0.1.0", upper = v"0.3.0")
CodecLz4: VersionNumber[v"0.4.6"]
Mera: VersionNumber[v"1.4.5"]
-------------------------
Memory: 1.68808214366436 GB (uncompressed)


Datatype: hydro
merafile_version: 1.0
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0xc0, 0xa4, 0xfe, 0x2a, 0x01, 0x00, 0x00, 0x00, 0xc0, 0x26, 0x24, 0x82, 0x01, 0x00, 0x00, 0x00, 0xf0, 0xe3, 0xae], false)
CodecZlib: VersionNumber[v"0.7.8"]
merafile_version: 1.0
JLD2: VersionNumber[v"0.5.13"]
CodecBzip2: VersionNumber[v"0.8.5"]
JLD2compatible_versions: (lower = v"0.1.0", upper = v"0.3.0")
CodecLz4: VersionNumber[v"0.4.6"]
Mera: VersionNumber[v"1.4.5"]
-------------------------
Memory: 2.3211056170985103 GB (uncompressed)


-----------------------------------
convert stat: false
-----------------------------------
Total file size: 2.159 GB
-----------------------------------






Dict{Any, Any} with 4 entries:
  "particles" => Dict{Any, Any}("versions"=>Dict{Any, Any}("CodecZlib"=>Version…
  "FileSize"  => (2.159, "GB")
  "gravity"   => Dict{Any, Any}("versions"=>Dict{Any, Any}("CodecZlib"=>Version…
  "hydro"     => Dict{Any, Any}("versions"=>Dict{Any, Any}("CodecZlib"=>Version…

Information about the content, etc. is returned in a dictionary.

Get a detailed tree-view of the data-file:

vd = viewdata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", showfull=true)
[Mera]: 2025-06-21T22:40:42.532

Mera-file output_00300.jld2 contains:

 ├─📂 hydro
 │  ├─🔢 data
 │  ├─🔢 info
 │  └─📂 information
 │     ├─🔢 compression
 │     ├─🔢 comments
 │     ├─🔢 storage
 │     ├─🔢 memory
 │     └─📂 versions
 │        ├─🔢 merafile_version
 │        ├─🔢 JLD2compatible_versions
 │        ├─🔢 CodecLz4
 │        ├─🔢 JLD2
 │        ├─🔢 CodecBzip2
 │        ├─🔢 Mera
 │        └─🔢 CodecZlib
 ├─📂 particles
 │  ├─🔢 data
 │  ├─🔢 info
 │  └─📂 information
 │     ├─🔢 compression
 │     ├─🔢 comments
 │     ├─🔢 storage
 │     ├─🔢 memory
 │     └─📂 versions
 │        ├─🔢 merafile_version
 │        ├─🔢 JLD2compatible_versions
 │        ├─🔢 CodecLz4
 │        ├─🔢 JLD2
 │        ├─🔢 CodecBzip2
 │        ├─🔢 Mera
 │        └─🔢 CodecZlib
 └─📂 gravity
    ├─🔢 data
    ├─🔢 info
    └─📂 information
       ├─🔢 compression
       ├─🔢 comments
       ├─🔢 storage
       ├─🔢 memory
       └─📂 versions
          ├─🔢 merafile_version
          ├─🔢 JLD2compatible_versions
          ├─🔢 CodecLz4
          ├─🔢 JLD2
          ├─🔢 CodecBzip2
          ├─🔢 Mera
          └─🔢 CodecZlib

Datatype: particles
merafile_version: 1.0
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0xe0, 0x20, 0x71, 0x29, 0x01, 0x00, 0x00, 0x00, 0x70, 0x44, 0xc6, 0x2c, 0x01, 0x00, 0x00, 0x00, 0x90, 0xe3, 0x2a], false)
CodecZlib: VersionNumber[v"0.7.8"]
merafile_version: 1.0
JLD2: VersionNumber[v"0.5.13"]
CodecBzip2: VersionNumber[v"0.8.5"]
JLD2compatible_versions: (lower = v"0.1.0", upper = v"0.3.0")
CodecLz4: VersionNumber[v"0.4.6"]
Mera: VersionNumber[v"1.4.5"]
-------------------------
Memory: 38.44882392883301 MB (uncompressed)


Datatype: gravity
merafile_version: 1.0
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], false)
CodecZlib: VersionNumber[v"0.7.8"]
merafile_version: 1.0
JLD2: VersionNumber[v"0.5.13"]
CodecBzip2: VersionNumber[v"0.8.5"]
JLD2compatible_versions: (lower = v"0.1.0", upper = v"0.3.0")
CodecLz4: VersionNumber[v"0.4.6"]
Mera: VersionNumber[v"1.4.5"]
-------------------------
Memory: 1.68808214366436 GB (uncompressed)


Datatype: hydro
merafile_version: 1.0
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0xc0, 0xa4, 0xfe, 0x2a, 0x01, 0x00, 0x00, 0x00, 0xc0, 0x26, 0x24, 0x82, 0x01, 0x00, 0x00, 0x00, 0xf0, 0xe3, 0xae], false)
CodecZlib: VersionNumber[v"0.7.8"]
merafile_version: 1.0
JLD2: VersionNumber[v"0.5.13"]
CodecBzip2: VersionNumber[v"0.8.5"]
JLD2compatible_versions: (lower = v"0.1.0", upper = v"0.3.0")
CodecLz4: VersionNumber[v"0.4.6"]
Mera: VersionNumber[v"1.4.5"]
-------------------------
Memory: 2.3211056170985103 GB (uncompressed)


-----------------------------------
convert stat: false
-----------------------------------
Total file size: 2.159 GB
-----------------------------------






Dict{Any, Any} with 4 entries:
  "particles" => Dict{Any, Any}("versions"=>Dict{Any, Any}("CodecZlib"=>Version…
  "FileSize"  => (2.159, "GB")
  "gravity"   => Dict{Any, Any}("versions"=>Dict{Any, Any}("CodecZlib"=>Version…
  "hydro"     => Dict{Any, Any}("versions"=>Dict{Any, Any}("CodecZlib"=>Version…

Get Info

The following function infodata is comparable to getinfo() used for the RAMSES files and loads detailed information about the simulation output:

info = infodata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/");
[Mera]: 2025-06-21T22:40:42.775

Use datatype: hydro
Code: RAMSES
output [300] summary:
mtime: 2023-04-09T05:34:09
ctime: 2025-06-21T18:31:24.020
=======================================================
simulation time: 445.89 [Myr]
boxlen: 48.0 [kpc]
ncpu: 640
ndim: 3
-------------------------------------------------------
amr:           true
level(s): 6 - 10 --> cellsize(s): 750.0 [pc] - 46.88 [pc]
-------------------------------------------------------
hydro:         true
hydro-variables:  7  --> (:rho, :vx, :vy, :vz, :p, :var6, :var7)
hydro-descriptor: (:density, :velocity_x, :velocity_y, :velocity_z, :pressure, :scalar_00, :scalar_01)
γ: 1.6667
-------------------------------------------------------
gravity:       true
gravity-variables: (:epot, :ax, :ay, :az)
-------------------------------------------------------
particles:     true
- Nstars:   5.445150e+05 
particle-variables: 7  --> (:vx, :vy, :vz, :mass, :family, :tag, :birth)
particle-descriptor: (:position_x, :position_y, :position_z, :velocity_x, :velocity_y, :velocity_z, :mass, :identity, :levelp, :family, :tag, :birth_time)
-------------------------------------------------------
rt:            false
clumps:           false
-------------------------------------------------------
namelist-file: ("&COOLING_PARAMS", "&HYDRO_PARAMS", "&SF_PARAMS", "&AMR_PARAMS", "&BOUNDARY_PARAMS", "&OUTPUT_PARAMS", "&POISSON_PARAMS", "&INIT_PARAMS", "&RUN_PARAMS", "&FEEDBACK_PARAMS", "&REFINE_PARAMS")
-------------------------------------------------------
timer-file:       true
compilation-file: false
makefile:         true
patchfile:        true
=======================================================

In this case, it loaded the InfoDataType from the hydro data. Choose a different stored datatype to get the info from:

info = infodata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", :particles);
[Mera]: 2025-06-21T22:40:43.264

Use datatype: particles
Code: RAMSES
output [300] summary:
mtime: 2023-04-09T05:34:09
ctime: 2025-06-21T18:31:24.020
=======================================================
simulation time: 445.89 [Myr]
boxlen: 48.0 [kpc]
ncpu: 640
ndim: 3
-------------------------------------------------------
amr:           true
level(s): 6 - 10 --> cellsize(s): 750.0 [pc] - 46.88 [pc]
-------------------------------------------------------
hydro:         true
hydro-variables:  7  --> (:rho, :vx, :vy, :vz, :p, :var6, :var7)
hydro-descriptor: (:density, :velocity_x, :velocity_y, :velocity_z, :pressure, :scalar_00, :scalar_01)
γ: 1.6667
-------------------------------------------------------
gravity:       true
gravity-variables: (:epot, :ax, :ay, :az)
-------------------------------------------------------
particles:     true
- Nstars:   5.445150e+05 
particle-variables: 7  --> (:vx, :vy, :vz, :mass, :family, :tag, :birth)
particle-descriptor: (:position_x, :position_y, :position_z, :velocity_x, :velocity_y, :velocity_z, :mass, :identity, :levelp, :family, :tag, :birth_time)
-------------------------------------------------------
rt:            false
clumps:           false
-------------------------------------------------------
namelist-file: ("&COOLING_PARAMS", "&HYDRO_PARAMS", "&SF_PARAMS", "&AMR_PARAMS", "&BOUNDARY_PARAMS", "&OUTPUT_PARAMS", "&POISSON_PARAMS", "&INIT_PARAMS", "&RUN_PARAMS", "&FEEDBACK_PARAMS", "&REFINE_PARAMS")
-------------------------------------------------------
timer-file:       true
compilation-file: false
makefile:         true
patchfile:        true
=======================================================

Load The Data from JLD2

Full Data

gas = loaddata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", :hydro);
[Mera]: 2025-06-21T22:40:43.330

Open Mera-file output_00300.jld2:

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]

Memory used for data table :2.321105550043285 GB
-------------------------------------------------------
typeof(gas)
HydroDataType
part = loaddata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", :particles);
[Mera]: 2025-06-21T22:40:46.833

Open Mera-file output_00300.jld2:

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]

Memory used for data table :38.44854164123535 MB
-------------------------------------------------------
typeof(part)
PartDataType

Data Range

Complete data is loaded, and the selected subregion is returned:

gas = loaddata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", :hydro,
                    xrange=[-10,10], 
                    yrange=[-10,10], zrange=[-2,2],
                    center=[:boxcenter], 
                    range_unit=:kpc);
[Mera]: 2025-06-21T22:40:47.294

Open Mera-file output_00300.jld2:

center: [0.5, 0.5, 0.5] ==> [24.0 [kpc] :: 24.0 [kpc] :: 24.0 [kpc]]

domain:
xmin::xmax: 0.2916667 :: 0.7083333  	==> 14.0 [kpc] :: 34.0 [kpc]
ymin::ymax: 0.2916667 :: 0.7083333  	==> 14.0 [kpc] :: 34.0 [kpc]
zmin::zmax: 0.4583333 :: 0.5416667  	==> 22.0 [kpc] :: 26.0 [kpc]

Memory used for data table :587.32142162323 MB
-------------------------------------------------------

Convert RAMSES Output Into JLD2

Existing AMR, hydro, gravity, particle, and clump data is sequentially stored in a JLD2 file. The individual loading/writing processes are timed, and the memory usage is returned in a dictionary:

Full Data

cvd = convertdata(300, path="/Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10",
                  fpath="/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/");
[Mera]: 2025-06-21T22:41:32.730

Requested datatypes: [:hydro, :gravity, :particles, :clumps]

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]


reading/writing lmax: 10 of 10
-----------------------------------
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x96, 0x25], false)
-----------------------------------
- hydro
Reading data...


Progress: 100%|█████████████████████████████████████████| Time: 0:00:59


- gravity
Reading data...


Progress: 100%|█████████████████████████████████████████| Time: 0:00:55


- particles


Progress: 100%|█████████████████████████████████████████| Time: 0:00:07



Total datasize:
- total folder: 5.682 GB
- selected: 5.68 GB
- used: 4.047 GB
- new on disc: 2.159 GB

Timer

Get a view of the timers:

using TimerOutputs
cvd
Dict{Any, Any} with 3 entries:
  "viewdata"     => Dict{Any, Any}("particles"=>Dict{Any, Any}("versions"=>Dict…
  "size"         => Dict{Any, Any}("folder"=>Any[6101111412, "Bytes"], "selecte…
  "TimerOutputs" => Dict{Any, Any}("writing"=>─────────────────────────────────…
cvd["TimerOutputs"]["reading"]
──────────────────────────────────────────────────────────────────────
                             Time                    Allocations      
                    ───────────────────────   ────────────────────────
 Tot / % measured:        174s /  94.4%           82.3GiB /  83.0%    

Section     ncalls     time    %tot     avg     alloc    %tot      avg
──────────────────────────────────────────────────────────────────────
hydro            1    96.6s   58.7%   96.6s   47.9GiB   70.2%  47.9GiB
gravity          1    58.9s   35.8%   58.9s   19.4GiB   28.4%  19.4GiB
particles        1    8.98s    5.5%   8.98s   0.98GiB    1.4%  0.98GiB
──────────────────────────────────────────────────────────────────────
cvd["TimerOutputs"]["writing"]
──────────────────────────────────────────────────────────────────────
                             Time                    Allocations      
                    ───────────────────────   ────────────────────────
 Tot / % measured:        174s /   5.0%           82.3GiB /  17.0%    

Section     ncalls     time    %tot     avg     alloc    %tot      avg
──────────────────────────────────────────────────────────────────────
hydro            1    5.01s   56.9%   5.01s   7.18GiB   51.4%  7.18GiB
gravity          1    3.42s   38.9%   3.42s   6.63GiB   47.5%  6.63GiB
particles        1    368ms    4.2%   368ms    159MiB    1.1%   159MiB
──────────────────────────────────────────────────────────────────────
# prep timer
to = TimerOutput();
@timeit to "MERA" begin
    @timeit to "hydro"     gas = loaddata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", :hydro, )
    @timeit to "particles" part= loaddata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", :particles)
end;
[Mera]: 2025-06-21T22:44:27.384

Open Mera-file output_00300.jld2:

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]

Memory used for data table :2.321105550043285 GB
-------------------------------------------------------

[Mera]: 2025-06-21T22:44:34.296

Open Mera-file output_00300.jld2:

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]

Memory used for data table :38.44854164123535 MB
-------------------------------------------------------
to
────────────────────────────────────────────────────────────────────────
                               Time                    Allocations      
                      ───────────────────────   ────────────────────────
  Tot / % measured:        7.22s /  97.5%           14.0GiB /  99.7%    

Section       ncalls     time    %tot     avg     alloc    %tot      avg
────────────────────────────────────────────────────────────────────────
MERA               1    7.05s  100.0%   7.05s   14.0GiB  100.0%  14.0GiB
  hydro            1    6.91s   98.1%   6.91s   13.8GiB   98.7%  13.8GiB
  particles        1    134ms    1.9%   134ms    180MiB    1.3%   180MiB
────────────────────────────────────────────────────────────────────────

<div class="alert alert-block alert-info"> <b>NOTE</b> The reading from JLD2 files is multiple times faster than from the original RAMSES files. </div>

Used Memory

cvd["size"]
Dict{Any, Any} with 4 entries:
  "folder"   => Any[6101111412, "Bytes"]
  "selected" => Any[6.09885e9, "Bytes"]
  "ondisc"   => Any[2318210927, "Bytes"]
  "used"     => Any[4.34515e9, "Bytes"]

<div class="alert alert-block alert-info"> <b>NOTE</b> The compressed JLD2 file takes a significantly smaller disk space than the original RAMSES folder.</div>

factor = cvd["size"]["folder"][1] / cvd["size"]["ondisc"][1]
println("==============================================================================")
println("In this example, the disk space is reduced by a factor of $factor !!")
println("==============================================================================")
==============================================================================
In this example, the disk space is reduced by a factor of 2.631818934567553 !!
==============================================================================

Selected Datatypes

cvd = convertdata(300, [:hydro, :particles], 
                  path="/Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10",
                  fpath="/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/");
[Mera]: 2025-06-21T22:44:34.761

Requested datatypes: [:hydro, :particles]

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]


reading/writing lmax: 10 of 10
-----------------------------------
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0xe3, 0x2a], false)
-----------------------------------
- hydro
Reading data...


Progress: 100%|█████████████████████████████████████████| Time: 0:00:57


- particles


Progress: 100%|█████████████████████████████████████████| Time: 0:00:07



Total datasize:
- total folder: 5.682 GB
- selected: 4.002 GB
- used: 2.359 GB
- new on disc: 1.306 GB

Compression

By default, the data is compressed by a standard compressor. Therefore, if you want to use a different compression algorithm better suited to your needs, you can also directly pass a compressor. https://juliaio.github.io/JLD2.jl/stable/compression/

LibraryCompressor
CodecZlib.jlZlibCompressorThe default as it is very widely used.
CodecBzip2.jlBzip2CompressorCan often times be faster
CodecLz4.jlLZ4FrameCompressorFast, but not compatible to the LZ4 shipped by HDF5

To use any of these, replace the compress = true argument with an instance of the compressor, e.g.

using CodecZlib
cvd = convertdata(300, [:hydro, :particles], compress=ZlibCompressor(),
                  path="/Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10",
                  fpath="/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/");
[Mera]: 2025-06-21T22:46:24.922

Requested datatypes: [:hydro, :particles]

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]


reading/writing lmax: 10 of 10
-----------------------------------
Compression: ZlibCompressor(level=-1, windowbits=15)
-----------------------------------
- hydro
Reading data...


Progress: 100%|█████████████████████████████████████████| Time: 0:00:57


- particles


Progress: 100%|█████████████████████████████████████████| Time: 0:00:07



Total datasize:
- total folder: 5.682 GB
- selected: 4.002 GB
- used: 2.359 GB
- new on disc: 1.241 GB
savedata(gas, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", 
            fmode=:write, compress=ZlibCompressor());
[Mera]: 2025-06-21T22:48:55.105


Create file: output_00300.jld2
Directory: /Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10
-----------------------------------
merafile_version: 1.0  -  Simulation code: RAMSES
-----------------------------------
DataType: hydro  -  Data variables: (:level, :cx, :cy, :cz, :rho, :vx, :vy, :vz, :p, :var6, :var7)
-----------------------------------
I/O mode: write  -  Compression: ZlibCompressor(level=-1, windowbits=15)
-----------------------------------
CodecLz4  0.4.6
JLD2  0.5.13
CodecBzip2  0.8.5
Mera  1.4.5
CodecZlib  0.7.8
-----------------------------------
Memory size: 2.321 GB (uncompressed)
Total file size: 1.213 GB
-----------------------------------

Get more information about the parameters of the compressor:

?ZlibCompressor
search: ZlibCompressor ZlibDecompressor GzipCompressor ZlibCompressorStream
ZlibCompressor(;level=-1, windowbits=15)

Create a zlib compression codec.

Arguments

  • level (-1..9): compression level. 1 gives best speed, 9 gives best compression, 0 gives no compression at all (the input data is simply copied a block at a time). -1 requests a default compromise between speed and compression (currently equivalent to level 6).
  • windowbits (9..15): size of history buffer is 2^windowbits.
Warning

serialize and deepcopy will not work with this codec due to stored raw pointers.

Comments

Add a description to the files:

comment = "The simulation is...."
cvd = convertdata(300, [:hydro, :particles], comments=comment,
                  path="/Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10",
                  fpath="/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/");
[Mera]: 2025-06-21T22:49:38.415

Requested datatypes: [:hydro, :particles]

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]


reading/writing lmax: 10 of 10
-----------------------------------
Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0xe3, 0x2a], false)
-----------------------------------
- hydro
Reading data...


Progress: 100%|█████████████████████████████████████████| Time: 0:00:57


- particles


Progress: 100%|█████████████████████████████████████████| Time: 0:00:07



Total datasize:
- total folder: 5.682 GB
- selected: 4.002 GB
- used: 2.359 GB
- new on disc: 1.306 GB
comment = "The simulation is...."
savedata(gas, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", comments=comment, fmode=:write);
[Mera]: 2025-06-21T22:51:29.166


Create file: output_00300.jld2
Directory: /Volumes/FASTStorage/Simulations/Mera-Tests/mw_L10
-----------------------------------
merafile_version: 1.0  -  Simulation code: RAMSES
-----------------------------------
DataType: hydro  -  Data variables: (:level, :cx, :cy, :cz, :rho, :vx, :vy, :vz, :p, :var6, :var7)
-----------------------------------
I/O mode: write  -  Compression: CodecLz4.LZ4FrameCompressor(Ptr{CodecLz4.LZ4F_cctx} @0x0000000000000000, Base.RefValue{CodecLz4.LZ4F_preferences_t}(CodecLz4.LZ4F_preferences_t(CodecLz4.LZ4F_frameInfo_t(0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0000000000000000, 0x00000000, 0x00000000), 0, 0x00000000, (0x00000000, 0x00000000, 0x00000000, 0x00000000))), UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0xe3, 0x2a], false)
-----------------------------------
CodecLz4  0.4.6
JLD2  0.5.13
CodecBzip2  0.8.5
Mera  1.4.5
CodecZlib  0.7.8
-----------------------------------
Memory size: 2.321 GB (uncompressed)
Total file size: 1.276 GB
-----------------------------------

Load the comment (hydro) from JLD2 file:

vd = viewdata(300, "/Volumes/FASTStorage/Simulations/Mera-Tests/JLD2_files/", verbose=false);
vd["hydro"]["comments"]
"The simulation is...."