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Experiment Management

Data science and ML are iterative processes that require a large number of attempts to reach a certain level of a metric. Experimentation is part of the development of data features, hyperspace exploration, deep learning optimization, etc. DVC helps you codify and manage all of your experiments, supporting these main approaches:

  1. Create experiments that derive from your latest project version without having to track them manually. DVC does that automatically, letting you list and compare them. The best ones can be made persistent, and the rest archived.
  2. Place in-code checkpoints that mark a series of variations, forming a deep experiment. DVC helps you capture them at runtime, and manage them in batches.
  3. Make experiments or checkpoints persistent by committing them to your repository. Or create these versions from scratch like typical project changes.

    At this point you may also want to consider the different ways to organize experiments in your project (as Git branches, as folders, etc.).

DVC also provides specialized features to codify and analyze experiments. Parameters are simple values you can tweak in a human-readable text file, which cause different behaviors in your code and models. On the other end, metrics (and plots) let you define, visualize, and compare meaningful measures for the experimental results.

๐Ÿ‘จโ€๐Ÿ’ป See Get Started: Experiments for a hands-on introduction to DVC experiments.

Experiments

โš ๏ธ This feature is only available in DVC 2.0 โš ๏ธ

dvc exp commands let you automatically track a variation to an established data pipeline. You can create multiple isolated experiments this way, as well as review, compare, and restore them later, or roll back to the baseline. The basic workflow goes like this:

  • Modify stage parameters or other dependencies (e.g. input data, source code) of committed stages.
  • Use dvc exp run (instead of repro) to execute the pipeline. The results are reflected in your workspace, and tracked automatically.
  • Use metrics to identify the best experiment(s).
  • Visualize, compare experiments with dvc exp show or dvc exp diff. Repeat ๐Ÿ”„
  • Use dvc exp apply to roll back to the best one.
  • Make the selected experiment persistent by committing its results to Git. This cleans the slate so you can repeat the process.

Checkpoints in source code

โš ๏ธ This feature is only available in DVC 2.0 โš ๏ธ

To track successive steps in a longer experiment, you can write your code so it registers checkpoints with DVC at runtime. This allows you, for example, to track the progress in deep learning techniques such as evolving neural networks.

This kind of experiment can also derive from a stable project version, but it tracks a series of variations (the checkpoints). You interact with them using dvc exp run and its --rev, --reset options (see also the checkpoint field in dvc.yaml outs).

To learn the main ways to use checkpoint experiments hands-on, please see our sample dvc-checkpoints-mnist repo.

Persistent experiments

When your experiments are good enough to save or share, you may want to store them persistently as Git commits in your repository.

Whether the results were produced with dvc repro directly, or after a dvc exp workflow (refer to previous sections), the dvc.yaml and dvc.lock pair in the workspace will codify the experiment as a new project version. The right outputs (including metrics) should also be present, or available via dvc checkout.

Organization patterns

DVC takes care of arranging dvc exp experiments and the data cache under the hood. But when it comes to full-blown persistent experiments, it's up to you to decide how to organize them in your project. These are the main alternatives:

  • Git tags and branches - use the repo's "time dimension" to distribute your experiments. This makes the most sense for experiments that build on each other. Helpful if the Git revisions can be easily visualized, for example with tools like GitHub.
  • Directories - the project's "space dimension" can be structured with directories (folders) to organize experiments. Useful when you want to see all your experiments at the same time (without switching versions) by just exploring the file system.
  • Hybrid - combining an intuitive directory structure with a good repo branching strategy tends to be the best option for complex projects. Completely independent experiments live in separate directories, while their progress can be found in different branches.

Automatic log of stage runs (run-cache)

Every time you dvc repro pipelines or dvc exp run experiments, DVC logs the unique signature of each stage run (to .dvc/cache/runs by default). If it never happened before, the stage command(s) are executed normally. Every subsequent time a stage runs under the same conditions, the previous results can be restored instantly, without wasting time or computing resources.

โœ… This built-in feature is called run-cache and it can dramatically improve performance. It's enabled out-of-the-box (but can be disabled with the --no-run-cache command option).

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