mantis

Mantis: A Fast, Small, and Exact Large-Scale Sequence-Search Index

Overview

Mantis is a space-efficient data structure that can be used to index thousands of raw- read experiments and facilitate large-scale sequence searches on those experiments. Mantis uses counting quotient filters instead of Bloom filters, enabling rapid index builds and queries, small indexes, and exact results, i.e., no false positives or negatives. Furthermore, Mantis is also a colored de Bruijn graph representation, so it supports fast graph traversal and other topological analyses in addition to large-scale sequence-level searches.

A preprint of the paper describing mantis is available here.

API

• mantis build: builds a mantis index from a collection of (squeakr) CQF files.
• mantis query: query k-mers in the mantis index.

Build

Library dependencies (given version or higher):

• libboost-dev 1.58.0.1ubuntu1
• zlib1g-dev 1:1.2.8.dfsg-2ubuntu4
• sdsl

The CQF code uses two new instructions to implement select on machine words introduced in intel's Haswell line of CPUs. However, there is also an alternate implementation of select on machine words to work on CPUs older than Haswell. To build on an older hardware (older than Haswell) use "NH=1" as a make argument.

mantis build creates a colored de Bruijn graph representation that can be used to query transcripts.

 $ make mantis
 $ ./mantis build -i raw/incqfs.lst -c raw/experiment_cutoffs.lst -o raw/

The usage for this command are as follows:

SYNOPSIS
        mantis build -i <input_list> -c <cutoff_list> -o <build_output>

OPTIONS
        <input_list>
                    file containing list of input filters

        <cutoff_list>
                    file containing list of experiment-specific cutoffs

        <build_output>
                    directory where results should be written

Following are the arguments to coloreddbg:

• input cqf files: a list of input cqf files. This is a list of squeakr output files that are generated after running squeakr on input experiments. We have provided two sample cqf files in data dir.
• experiment cutoffs: The cutoff value for each input cqf file corresponding to the experiment. The cutoff value is the minimum count that a k-mer needs to be considered in the search.
• prefix: prefix filepath where all the output files will be written.

Query

mantis query lets you query a mantis index with a set of sequences.

 $ make mantis
 $ ./mantis query -p raw/ -o query.res raw/input_txns.fa

The options and arguments are as follows:

SYNOPSIS
        mantis query [-j] -p <query_prefix> [-o <output_file>] <query>

OPTIONS
        -j, --json  Write the output in JSON format

        <query_prefix>
                    Prefix of input files.

        <output_file>
                    Where to write query output.

        <query>     Prefix of input files.

The command takes the following options :

• --input-prefix,-p: the directory where the output of coloreddbg command is present.
• --output,-o: the file where the query results should be written (default : samples.output).

additionally the command takes the following mandatory positional argument :

• query transcripts: input transcripts to be queried.

Finally, rather than writing the results in the "simple" output format, they can be written in JSON if you provide the --json,-j flag to the query comamnd.

The output file in contains the list of experiments (i.e., hits) corresponding to each queried transcript.

Contributing

Contributions via GitHub pull requests are welcome.

Authors

• Prashant Pandey [email protected]
• Rob Johnson [email protected]
• Rob Patro [email protected]