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Pyserini: Detailed Installation Guide

Pyserini is built on Python 3.10. At a high level, we try to keep our requirements.txt up to date. Pyserini has a number of important dependencies:

  • For sparse retrieval, Pyserini depends on Anserini, which is built on Lucene. PyJNIus is used to interact with the JVM.
  • For dense retrieval (since it involves neural networks), we need the 🤗 Transformers library, PyTorch, and Faiss (specifically faiss-cpu). A pip installation will automatically pull in the first to satisfy the package requirements, but since the other two may require platform-specific custom configuration, they are not explicitly listed in the package requirements. We leave the installation of these packages to you (but provide detailed instructions below).

PyPI Installation Walkthrough

Below is a step-by-step Pyserini installation guide based on Python 3.10.


We recommend using Anaconda and assume you have already installed it.

Create new environment:

conda create -n pyserini python=3.10 -y
conda activate pyserini

If you do not already have JDK 21 installed, install via conda:

conda install -c conda-forge openjdk=21 maven -y

If your system already has JDK 21 installed, the above step can be skipped. Use java --version to check one way or the other.

If you're on an Intel-based Mac, the following recipe should work:

conda install wget -y
conda install -c conda-forge openjdk=21 maven -y
conda install -c conda-forge lightgbm nmslib -y

# from
# NOTE: due to a bug in the latest 1.7.4 release, Intel MKL 2021 needs to be installed separately where applicable.
conda install -c pytorch faiss-cpu=1.7.4 mkl=2021 blas=1.0=mkl -y
conda install -c pytorch pytorch -y

pip install pyserini

If you're on a Mac with an M-series (i.e., ARM) processor, the following recipe should work:

conda install wget -y
conda install -c conda-forge openjdk=21 maven -y
conda install -c conda-forge lightgbm nmslib -y
conda install -c pytorch faiss-cpu pytorch -y

pip install pyserini

As of April 2024, for faiss-cpu, osx-64 is still at v1.7.4, whereas osx-arm64 is at v1.8.0; hence the differences in the instructions above.


On Linux, pip is an alternative that's a bit more lightweight:

pip install torch faiss-cpu
pip install pyserini

Verifying the Installation

By this point, Pyserini should have been installed. It might be worthwhile to do a bit of sanity checking, per below.

To confirm that bag-of-words retrieval is working correctly, you can run the BM25 baseline on the MS MARCO passage ranking task:

$ python -m \
    --topics msmarco-passage-dev-subset \
    --index msmarco-v1-passage \
    --output run.msmarco-passage.txt \
    --output-format msmarco \

$ python -m pyserini.eval.msmarco_passage_eval msmarco-passage-dev-subset run.msmarco-passage.txt
MRR @10: 0.18741227770955546
QueriesRanked: 6980

To confirm that dense retrieval is working correctly, you can run our TCT-ColBERT (v2) model on the MS MARCO passage ranking task:

$ python -m \
    --topics msmarco-passage-dev-subset \
    --index msmarco-v1-passage.tct_colbert-v2-hnp \
    --encoded-queries tct_colbert-v2-hnp-msmarco-passage-dev-subset \
    --threads 12 --batch-size 384 \
    --output \
    --output-format msmarco

$ python -m pyserini.eval.msmarco_passage_eval msmarco-passage-dev-subset
MRR @10: 0.3584
QueriesRanked: 6980

If everything is working properly, you should be able to reproduce the results above.

Development Installation

If you're planning on just using Pyserini, then the instructions above are fine. However, if you're planning on contributing to the codebase or want to work with the latest not-yet-released features, you'll need a development installation.

Start the same way as the install above, but don't install pip install pyserini.

Instead, clone the Pyserini repo with the --recurse-submodules option to make sure the tools/ submodule also gets cloned:

git clone --recurse-submodules

The tools/ directory, which contains evaluation tools and scripts, is actually this repo, integrated as a Git submodule (so that it can be shared across related projects). Change into the pyserini subdirectory and build as follows (you might get warnings, but okay to ignore):

cd tools/eval && tar xvfz trec_eval.9.0.4.tar.gz && cd trec_eval.9.0.4 && make && cd ../../..
cd tools/eval/ndeval && make && cd ../../..

Then, in the pyserini clone, use pip to add an "editable" installation, as follows:

pip install -e .

You'll need to download the Spacy English model to reproduce tasks such as LTR Filtering for MS MARCO Passage.

python -m spacy download en_core_web_sm

Next, you'll need to clone and build Anserini. It makes sense to put both pyserini/ and anserini/ in a common folder. After you've successfully built Anserini, copy the fatjar, which will be target/anserini-X.Y.Z-SNAPSHOT-fatjar.jar into pyserini/resources/jars/. As with the pip installation, a potential source of frustration is incompatibility among different versions of underlying dependencies.

You can confirm everything is working by running the unit tests:

python -m unittest

Assuming all tests pass, you should be ready to go!

Troubleshooting Tips

  • The above guide handle JVM installation via conda. If you are using your own Java environment and get an error about Java version mismatch, it's likely an issue with your JAVA_HOME environmental variable. In bash, use echo $JAVA_HOME to find out what the environmental variable is currently set to, and use export JAVA_HOME=/path/to/java/home to change it to the correct path. On a Linux system, the correct path might look something like /usr/lib/jvm/java-21. Unfortunately, we are unable to offer more concrete advice since the actual path depends on your OS, which JDK you're using, and a host of other factors.
  • On Apple's M-series processors, make sure you've installed the ARM-based release of Conda instead of the Intel-based release.

Internal Notes

At the University of Waterloo, we have two (CPU) development servers, tuna and orca. Note that on these two servers, the root disk (where your home directory is mounted) doesn't have much space. So, you need to set pyserini cache path to scratch space.

  • For tuna, create the dir /tuna1/scratch/{username}
  • For ocra, create the dir /store/scratch/{username}

Set the PYSERINI_CACHE environment variable to point to the directory you created above.