Brisera

A Python implementation of a distributed seed and reduce algorithm (similar to BlastReduce and CloudBurst) that utilizes RDDs (resilient distributed datasets) to perform fast iterative analyses and dynamic programming without relying on chained MapReduce jobs.

Quick Start

The code is organized as follows:

• apps/ - this directory contains the SparkApplications to be run
• brisera/ - this is the python module with the code
• tests/ - contains a stub testing library for ensuring things work
• fixtures/ - contains reference data for running the apps against
• docs/ - stubs for documentation for the project

To install the required dependencies:

$ pip install -r requirements.txt

The code for Brisera is found in the brisera Python module. This module must be available to the spark applications (e.g. able to be imported) either by running the spark applications locally in the working directory that contains brisera or by using a virtual environment (recommended). You can install brisera and all dependencies, use the setup.py function:

$ python setup.py install

But note that you will still have to have access to the Spark applications that are in the apps/ directory - don't delete them out of hand!

Usage

To read a burst sequence file (e.g. fixtures/cloudburst/100k.br) in order to compare results from CloudBurst to Brisera, you can use the read_burst.py Spark application as follows:

$ spark-submit --master local[*] apps/read_burst.py <sequence_file> <output_dir>

This will write out each record (or chunk) from the sequence file to a text file on disk.

To convert a FASTA file for use with Brisera alignments, you can use the convert_fasta.py Spark application as follows:

$ spark-submit --master local[*] apps/convert_fasta.py input.fa output.ser

This command will transform a single FASTA file into a chunked, binary format that can be used with Spark in a computationally efficient way (preparing the chunks for seed reduce).

To compute alignments, use the brisera_align.py Spark application. Note that this application takes its configuration from the conf/brisera.yaml file, an example of which is included. You can modify the configuration for the app by modifying that file. Run the alignment as follows:

$ spark-submit --master local[*] apps/brisera_align.py refpath qrypath outpath

The input is as follows:

• The refpath is the converted FASTA file of the reference genome you wish to align to
• The qrypath is the set of queries or reads that you would like aligned to the reference
• The outpath is where the alignment information will be written to when complete

Depending on the value you set for K, this could take seconds to hours; be aware of how modifying the settings can change things!

Other Details

Brisera means to "explode" or to "burst" in Swedish. Since I'm reworking CloudBurst and BlastReduce (both of which use BLAST) to Spark (weirdly all the same terminology) it felt right to name the project something burst/explode related. (I tried a few languages, but Swedish had the best result).

References

1. M. C. Schatz, “BlastReduce: high performance short read mapping with MapReduce,” University of Maryland, [http://cgis. cs.umd.edu/Grad/scholarlypapers/papers/MichaelSchatz](http://cgis. cs.umd.edu/Grad/scholarlypapers/papers/MichaelSchatz). pd f, 2008.

2. M. C. Schatz, “CloudBurst: highly sensitive read mapping with MapReduce,” Bioinformatics, vol. 25, no. 11, pp. 1363–1369, 2009.

3. X. Li, W. Jiang, Y. Jiang, and Q. Zou, “Hadoop Applications in Bioinformatics,” in Open Cirrus Summit (OCS), 2012 Seventh, 2012, pp. 48–52.

4. R. K. Menon, G. P. Bhat, and M. C. Schatz, “Rapid parallel genome indexing with MapReduce,” in Proceedings of the second international workshop on MapReduce and its applications, 2011, pp. 51–58.