TRIMMOMATIC SE

Trim single-end reads with trimmomatic. (De)compress with pigz.

Example

This wrapper can be used in the following way:

rule trimmomatic:
    input:
        "reads/{sample}.fastq.gz"  # input and output can be uncompressed or compressed
    output:
        "trimmed/{sample}.fastq.gz"
    log:
        "logs/trimmomatic/{sample}.log"
    params:
        # list of trimmers (see manual)
        trimmer=["TRAILING:3"],
        # optional parameters
        extra="",
        # optional compression levels from -0 to -9 and -11
        compression_level="-9"
    threads:
        32
    # optional specification of memory usage of the JVM that snakemake will respect with global
    # resource restrictions (https://snakemake.readthedocs.io/en/latest/snakefiles/rules.html#resources)
    # and which can be used to request RAM during cluster job submission as `{resources.mem_mb}`:
    # https://snakemake.readthedocs.io/en/latest/executing/cluster.html#job-properties
    resources:
        mem_mb=1024
    wrapper:
        "v4.6.0-24-g250dd3e/bio/trimmomatic/se"

Note that input, output and log file paths can be chosen freely.

When running with

snakemake --use-conda

the software dependencies will be automatically deployed into an isolated environment before execution.

Software dependencies

• trimmomatic==0.36

• pigz==2.3.4

• snakemake-wrapper-utils==0.1.3

Authors

• Johannes Köster

• Jorge Langa

Code

"""
bio/trimmomatic/se

Snakemake wrapper to trim reads with trimmomatic in SE mode with help of pigz.
pigz is the parallel implementation of gz. Trimmomatic spends most of the time
compressing and decompressing instead of trimming sequences. By using process
substitution (<(command), >(command)), we can accelerate trimmomatic a lot.
Consider providing this wrapper with at least 1 extra thread per each gzipped
input or output file.
"""

__author__ = "Johannes Köster, Jorge Langa"
__copyright__ = "Copyright 2016, Johannes Köster"
__email__ = "koester@jimmy.harvard.edu"
__license__ = "MIT"


from snakemake.shell import shell
from snakemake_wrapper_utils.java import get_java_opts


# Distribute available threads between trimmomatic itself and any potential pigz instances
def distribute_threads(input_file, output_file, available_threads):
    gzipped_input_files = 1 if input_file.endswith(".gz") else 0
    gzipped_output_files = 1 if output_file.endswith(".gz") else 0
    potential_threads_per_process = available_threads // (
        1 + gzipped_input_files + gzipped_output_files
    )
    if potential_threads_per_process > 0:
        # decompressing pigz creates at most 4 threads
        pigz_input_threads = (
            min(4, potential_threads_per_process) if gzipped_input_files != 0 else 0
        )
        pigz_output_threads = (
            (available_threads - pigz_input_threads * gzipped_input_files)
            // (1 + gzipped_output_files)
            if gzipped_output_files != 0
            else 0
        )
        trimmomatic_threads = (
            available_threads
            - pigz_input_threads * gzipped_input_files
            - pigz_output_threads * gzipped_output_files
        )
    else:
        # not enough threads for pigz
        pigz_input_threads = 0
        pigz_output_threads = 0
        trimmomatic_threads = available_threads
    return trimmomatic_threads, pigz_input_threads, pigz_output_threads


def compose_input_gz(filename, threads):
    if filename.endswith(".gz") and threads > 0:
        return "<(pigz -p {threads} --decompress --stdout {filename})".format(
            threads=threads, filename=filename
        )
    return filename


def compose_output_gz(filename, threads, compression_level):
    if filename.endswith(".gz") and threads > 0:
        return ">(pigz -p {threads} {compression_level} > {filename})".format(
            threads=threads, compression_level=compression_level, filename=filename
        )
    return filename


extra = snakemake.params.get("extra", "")
java_opts = get_java_opts(snakemake)
log = snakemake.log_fmt_shell(stdout=True, stderr=True)
compression_level = snakemake.params.get("compression_level", "-5")
trimmer = " ".join(snakemake.params.trimmer)

# Distribute threads
trimmomatic_threads, input_threads, output_threads = distribute_threads(
    snakemake.input[0], snakemake.output[0], snakemake.threads
)

# Collect files
input = compose_input_gz(snakemake.input[0], input_threads)
output = compose_output_gz(snakemake.output[0], output_threads, compression_level)

shell(
    "trimmomatic SE -threads {trimmomatic_threads} "
    "{java_opts} {extra} {input} {output} {trimmer} {log}"
)