conda vs mamba

Material for TGIF 28.05.2021

The snake pit

Here are the snakes we want to deal with:

• python: programming language
• conda: package manager ... made in python
• mamba: the same as conda ... just makes package installation faster!

Why conda?

• A package manager which can be used as normal user (no admin rights).
• You can build your own packages ... there is a community supporting you on conda-forge.
• You can create environments which contain all the packages you need.
• You can use conda environments to make your projects reproducible and interoperable.

https://docs.conda.io/en/latest/

Why mamba?

conda is slow when resolving dependencies from community sources like conda-forge. mamba is a re-implementation of conda in c++ to solve this issue.

https://github.com/mamba-org/mamba

How to install conda/mamba?

In this demo we won't install conda. See the document Installation.md for some hints. conda and mamba are already available on mistral.

Let's try it out in a web browser!

Right-click on the button, select open link in new tab, to run this demo with Binder:

It takes a while... and then a Jupyter app opens.

On the top right, you will find the button New. Please launch a Linux terminal with: New -> Terminal

Note: Binder has a timeout after 10 minutes of inactivity.

Working with conda

Configuration of active channels

Check which channels conda uses, i.e. where it looks for software packages

conda config --show-sources

conda-forge provides a lot of software packages that are relevant for our work. If conda-forge is not yet part of your channels you can add it with conda config --add channels conda-forge.

Create a new conda environment named tgif

We don't want to install in the conda base environment. On mistral this would also not be possible because you only have read-only access to the base enviromment.

So we have to create our own conda environment locally (default: in your HOME directory).

Create the tgif environment which has only Python 3.x included:

conda create --name tgif python=3

See what conda environments are available:

conda env list

Activate the tgif enviromment:

conda activate tgif

Check which conda packages are available.

List all available conda packages in your current (tgif) environment:

conda list

The cfchecker package is not yet available. Check if it could be installed via conda:

conda search cfchecker

Yes, we can! It is available on the conda-forge channel.

Install more packages into the tgif environment

Install the cfchecker:

conda install cfchecker

Apply the cfchecker on a single NetCDF file:

cfchecks test.nc

Compare installation with mamba and conda

Now, we want to install more packages:

• cdo: Climate Data Operators (https://code.mpimet.mpg.de/projects/cdo/)
• magics: ECMWF's plotting package (https://confluence.ecmwf.int/display/MAGP/Magics)

conda install cdo magics

Note: resolving environments takes forever! Interrupt with one or several Ctrl–C.

Try the same installation with mamba:

mamba install cdo magics

Note: resolving environments is much faster!

Test your cdo and magics installations

Print summary statistics with cdo

cdo infov test.nc

Create a png-plot with magics using a python script. If you like, have a look into the script with more magicsplot.py.

python magicsplot.py

Go to the Jupyter Home Page Tab, click on mymagicsplot.png to view the plot.

Save your tgif environment

Export your enviromment to an enviromment file (default: environment.yml):

conda env export --name tgif --from-history > environment.yml

Deactivate and remove the tgif environment

Deactivate your tgif environment, going back to conda base:

conda deactivate

Remove your tgif environment:

conda env remove --name tgif

Check with:

conda env list

Create tgif environment again

Create tgif environment from environment.yml file (default):

mamba env create

OR

mamba env create -f environment.yml

Activate the tgif environment:

conda activate tgif

Now you have reproduced your previous tgif environment.

Further topics

Reproducible environment with conda

Export download links of all packages of your environment:

conda list --explicit > spec-file.txt

Rebuild identical conda environment (not cross-platform):

conda create --file spec-file.txt --name tgif2

Reproducible environments with anaconda-project

https://anaconda-project.readthedocs.io/en/latest/

You can use it to make your Jupyter notebooks reproducible on different operating systems (Linux, macOS, Windows) with a complete list of all your dependent packages.