Visualization of different minimizer schemes supported in Digest and code example using library
What is the Digest library?
- a
C++
library that supports various sub-sampling schemes for $k$-mers in DNA sequences.
Digest
library utilizes the rolling hash-function from ntHash to order the $k$-mers in a window.
- a set of Python bindings that allow the user to run functions from the C++ library in Python.
How to install and build into your project?

Option 1: conda installation
Digest is available on bioconda. This installs both the C++ library and python library. The include
and lib
directories are in the conda environment dir (you can find it using conda env list
).
conda install -c bioconda digest
Option 2: Install from source
After cloning from GitHub, we use the Meson build-system to install the library.
PREFIX
is an absolute path to library files will be install (*.h
and *.a
files)
- IMPORTANT:
PREFIX
should not be the root directory of the digest/
repo to avoid any issues with installation.
- We suggest using
--prefix=$(pwd)/build
from within the root directory of the digest/
repo.
- These commands generate an
include
and lib
folders in PREFIX
folder
git clone https://github.com/VeryAmazed/digest.git
meson setup --prefix=<PREFIX> --buildtype=release build
meson install -C build
Step 2: Include Digest in your project
(a) Using Meson
:
If your coding project uses Meson
to build the executable(s), you can include a file called subprojects/digest.wrap
in your repository and let Meson install it for you.
(b) Using g++
:
To use Digest in your C++ project, you just need to include the header files (*.h
) and library file (*.a
) that were installed in the first step. Assuming that build/
is the directory you installed them in, here is how you can compile.
g++ -std=c++17 -o main main.cpp -I build/include/ -L build/lib -lnthash
Detailed Look at Example Usage (2 ways):
There are three types of minimizer schemes that can be used:
- Windowed Minimizer: classifies a kmer as a minimizer if it is the smallest in the user specifed large window, using rightmost kmer to break ties.
- Modimizer: classifies a kmer as a minimizer if the hash of the kmer is congruent to the user specified value in the user specified mod-space.
- Syncmer: classifies a large window as a minimizer if its smallest value is equal to the value of the hashes of the leftmost or rightmost kmer in the window (doesn't care if the smallest hash value is not unique). Note that because of how the large window is defined if you are using the SKIPOVER policy and your sequence has non-ACTG characters, it is possible for this large window to have varying lengths in terms of number of characters.
The general steps to use Digest is as follows: (1) include the relevant header files, (2) declare the Digest object and (3) find the positions where the minimizers are present in the sequence.
1. Find positions of minimizers:
#include "digest/digester.hpp"
#include "digest/window_minimizer.hpp"
std::vector<size_t> output;
digester.roll_minimizer(100, output);
Child class of Digester that defines a minimizer as a kmer whose hash is minimal among those in the l...
Definition window_minimizer.hpp:33
- This code snippet will find up to 100 Windowed Minimizers and store their positions in the vector called
output
.
digest::BadCharPolicy::WRITEOVER
means that anytime the code encounters an non-ACTG
character, it will replace it with an A
.
digest::ds::Adaptive
is our recommended data-structure for finding the minimum value in a window (see wiki for other options)
2. Find both positions and hash values of minimizers
If you would like to obtain both the positions and hash values for each minimizer, you can pass a vector of paired integers to do so.
std::vector<std::pair<size_t, size_t>> output;
digester.roll_minimizer(100, output);
Documentation:
Documentation generated with Doxygen can be found here
Python binding support
Included in the library are function bindings for each sub-sampling scheme for use in Python. The simplest way to install the python module is through conda (conda install bioconda::digest
). To install the Python module from source, first install the library with meson
(see above for detailed instructions), and install with pip
. For this setup, the meson
prefix must be set to --prefix=/$DIGEST_REPO/build
:
meson setup --prefix=$(pwd)/build --buildtype=release build
meson install -C build
pip install .
Alternatively, copy the lib
and include
directories from the earlier meson installation to a directory in the repo called build
, and run pip install .
We recommend using a conda or python virtual environment. Once installed, you can import and use the Digest library in Python:
>>> from digest import window_minimizer, syncmer, modimizer
>>> window_minimizer('ACGTACGTAGCTAGCTAGCTAGCTGATTACATACTGTATGCAAGCTAGCTGATCGATCGTAGCTAGTGATGCTAGCTAC', k=5, w=11)
[4, 5, 16, 19, 21, 26, 27, 35, 39, 49, 57, 63, 68]
>>> modimizer('ACGTACGTAGCTAGCTAGCTAGCTGATTACATACTGTATGCAAGCTAGCTGATCGATCGTAGCTAGTGATGCTAGCTAC', k=5, mod=5)
[23, 34, 38, 40, 62, 67]
>>> syncmer('ACGTACGTAGCTAGCTAGCTAGCTGATTACATACTGTATGCAAGCTAGCTGATCGATCGTAGCTAGTGATGCTAGCTAC', k=5, w=15)
[0, 3, 4, 5, 7, 12, 13, 27, 35, 49]
>>> modimizer('ATCGTGCATCA', k=4, mod=2, include_hash=True)
[(0, 1122099596), (2, 249346952), (4, 227670418), (7, 123749036)]
>>> seq = 'ACGTACGTAGCTAGCTAGCTAGCTGATTACATACTGTATGCAAGCTAGCTGATCGATCGTAGCTAGTGATGCTAGCTAC'
>>> [seq[p:p+5] for p in window_minimizer(seq, k=5, w=11)]
['ACGTA', 'CGTAG', 'AGCTA', 'TAGCT', 'GCTGA', 'TTACA', 'TACAT', 'GTATG', 'GCAAG', 'TGATC', 'CGTAG', 'TAGTG', 'ATGCT']
We have also implemented parallel execution in the python library:
>>> import timeit
>>> timeit.timeit('window_minimizer(seq, k=5, w=11)',
... setup='from digest import window_minimizer; seq = open("tests/bench/chrY.fa", "rb").read()',
... number=10)
19.85955114942044
>>> timeit.timeit('window_minimizer(seq, k=5, w=11, num_threads=4)',
... setup='from digest import window_minimizer; seq = open("tests/bench/chrY.fa", "rb").read()',
... number=10)
10.327348310500383
Functions can also return numpy arrays with the *_np
function variant:
>>> from digest import window_minimizer_np
>>> window_minimizer_np(b'ACGTACGTAGCTAGCTAGCTAGCTGATTACATACTGTATGCAAGCTAGCTGATCGATCGTAGCTAGTGATGCTAGCTAC', k=5, w=11)
array([ 4, 5, 16, 19, 21, 26, 27, 35, 39, 49, 57, 63, 68], dtype=uint32)
CLI
A basic cli can be found here
Benchmark / Tests
cd build
meson configure -Dbuildtype=debug
meson compile
This will set the build flage from release to debug allowing you to generate proper executables for benchmark/testing. The executables will be located in the build folder and can be run directly from there. You can look at the meson.build file for more details.
Rust Bindings
We include Rust bindings for the digest library. To use the Rust bindings, add the following to your Cargo.toml
:
[dependencies]
digest-rs = "0.1.0"
When compiling any package that uses digest-seq
, set the env variable DIGEST_DIR to the build directory after building with meson (or, alternatively, install with Conda).
Example Usage
use digest_rs;
// Window minimizer example
let sequence = "ACGTACGT";
let k = 4;
let window = 2;
let minimizers = digest_rs::window_minimizer_rs(sequence, k, window)?;
// Modimizer example
let mod_val = 3;
let modimizers = digest_rs::modimizer_rs(sequence, k, mod_val)?;
// Syncmer example
let syncmers = digest_rs::syncmer_rs(sequence, k, window)?;
The three primary functions are available as bindings to the C++ library (similar to the python bindings). All functions return a Result<Vec<u32>, DigestError>
containing the positions of the minimizers in the sequence.
- Note
- These are only Rust bindings of the C++ implementation, not a full Rust implementation. As such, they contain unsafe code blocks.
Contributing
Use clang format version 17.
run ninja clang-format
before submitting a PR.