Provided by: jellyfish1_1.1.11-4build1_amd64 
NAME
jellyfish1 - count k-mers in DNA sequences
SYNOPSIS
jellyfish count [-oprefix] [-mmerlength] [-tthreads] [-shashsize] [--both-strands] fasta [fasta ... ]
jellyfish merge hash1 hash2 ...
jellyfish dump hash
jellyfish stats hash
jellyfish histo [-hhigh] [-llow] [-iincrement] hash
jellyfish query hash
jellyfish cite
Plus equivalent version for Quake mode: qhisto, qdump and qmerge.
DESCRIPTION
Jellyfish is a k-mer counter based on a multi-threaded hash table implementation.
COUNTING AND MERGING
To count k-mers, use a command like:
jellyfish count -m 22 -o output -c 3 -s 10000000 -t 32 input.fasta
This will count the the 22-mers in input.fasta with 32 threads. The counter field in the hash uses only 3
bits and the hash has at least 10 million entries.
The output files will be named output_0, output_1, etc. (the prefix is specified with the -o switch). If
the hash is large enough (has specified by the -s switch) to fit all the k-mers, there will be only one
output file named output_0. If the hash filled up before all the mers were read, the hash is dumped to
disk, zeroed out and reading in mers resumes. Multiple intermediary files will be present on the disks,
named output_0, output_1, etc.
To obtain correct results from the other sub-commands (such as histo, stats, etc.), the multiple output
files, if any, need to be merged into one with the merge command. For example with the following command:
jellyfish merge -o output.jf output\_*
Should you get many intermediary output files (say hundreds), the size of the hash table is too small.
Rerunning Jellyfish with a larger size (option -s) is probably faster than merging all the intermediary
files.
ORIENTATION
When the orientation of the sequences in the input fasta file is not known, e.g. in sequencing reads,
using --both-strands (-C) makes the most sense.
For any k-mer m, its canonical representation is m itself or its reverse-complement, whichever comes
first lexicographically. With the option -C, only the canonical representation of the mers are stored in
the hash and the count value is the number of occurrences of both the mer and its reverse-complement.
CHOOSING THE HASH SIZE
To achieve the best performance, a minimum number of intermediary files should be written to disk. So the
parameter -s should be chosen to fit as many k-mers as possible (ideally all of them) while still fitting
in memory.
We consider to examples: counting mers in sequencing reads and in a finished genome.
First, suppose we count k-mers in short sequencing reads: there are n reads and there is an average of 1
error per reads where each error generates k unique mers. If the genome size is G, the size of the hash
(option -s) to fit all k-mers at once is estimated to: $(G + k*n)/0.8$. The division by 0.8 compensates
for the maximum usage of approximately $80%$ of the hash table.
On the other hand, when counting k-mers in an assembled sequence of length G, setting -s to G is
appropriate.
As a matter of convenience, Jellyfish understands ISO suffixes for the size of the hash. Hence '-s 10M'
stands 10 million entries while '-s 50G' stands for 50 billion entries.
The actual memory usage of the hash table can be computed as follow. The actual size of the hash will be
rounded up to the next power of 2: s=2^l. The parameter r is such that the maximum reprobe value (-p)
plus one is less than 2^r. Then the memory usage per entry in the hash is (in bits, not bytes) 2k-l+r+1.
The total memory usage of the hash table in bytes is: 2^l*(2k-l+r+1)/8.
CHOOSING THE COUNTING FIELD SIZE
To save space, the hash table supports variable length counter, i.e. a k-mer occurring only a few times
will use a small counter, a k-mer occurring many times will used multiple entries in the hash.
Important: the size of the couting field does NOT change the result, it only impacts the amount of memory
used. In particular, there is no maximum value in the hash. Even if the counting field uses 5 bits, a
k-mer occuring 2 million times will have a value reported of 2 million (i.e., it is not capped at 2^5).
The -c specify the length (in bits) of the counting field. The trade off is as follows: a low value will
save space per entry in the hash but can potentially increase the number of entries used, hence maybe
requiring a larger hash.
In practice, use a value for -c so that most of you k-mers require only 1 entry. For example, to count
k-mers in a genome, where most of the sequence is unique, use -c1 or -c2. For sequencing reads, use a
value for -c large enough to counts up to twice the coverage. For example, if the coverage is 10X, choose
a counter length of 5 (-c5) as $2^5 > 20$.
SUBCOMMANDS AND OPTIONS
COUNT
Usage: jellyfish count [options] file:path+
Count k-mers or qmers in fasta or fastq files
Options (default value in (), *required):
-m, --mer-len=uint32
*Length of mer
-s, --size=uint64
*Hash size
-t, --threads=uint32
Number of threads (1)
-o, --output=string
Output prefix (mer_counts)
-c, --counter-len=Length
in bits Length of counting field (7)
--out-counter-len=Length
in bytes Length of counter field in output (4)
-C,--both-strands
Count both strand, canonical representation (false)
-p, --reprobes=uint32
Maximum number of reprobes (62)
-r,--raw
Write raw database (false)
-q,--quake
Quake compatibility mode (false)
--quality-start=uint32
Starting ASCII for quality values (64)
--min-quality=uint32
Minimum quality. A base with lesser quality becomes an N (0)
-L, --lower-count=uint64
Don't output k-mer with count < lower-count
-U, --upper-count=uint64
Don't output k-mer with count > upper-count
--matrix=Matrix
file Hash function binary matrix
--timing=Timing
file Print timing information
--stats=Stats
file Print stats
--usage
Usage
-h,--help
This message
--full-help
Detailed help
-V,--version
Version
STATS
Usage: jellyfish stats [options] db:path
Statistics
Display some statistics about the k-mers in the hash:
Unique: Number of k-mers which occur only once. Distinct: Number of k-mers, not counting multiplicity.
Total: Number of k-mers, including multiplicity. Max_count: Maximum number of occurrence of a k-mer.
Options (default value in (), *required):
-L, --lower-count=uint64
Don't consider k-mer with count < lower-count
-U, --upper-count=uint64
Don't consider k-mer with count > upper-count
-v,--verbose
Verbose (false)
-o, --output=string
Output file
--usage
Usage
-h,--help
This message
--full-help
Detailed help
-V,--version
Version
HISTO
Usage: jellyfish histo [options] db:path
Create an histogram of k-mer occurrences
Create an histogram with the number of k-mers having a given count. In bucket 'i' are tallied the k-mers
which have a count 'c' satisfying 'low+i*inc <= c < low+(i+1)*inc'. Buckets in the output are labeled by
the low end point (low+i*inc).
The last bucket in the output behaves as a catchall: it tallies all k-mers with a count greater or equal
to the low end point of this bucket.
Options (default value in (), *required):
-l, --low=uint64
Low count value of histogram (1)
-h, --high=uint64
High count value of histogram (10000)
-i, --increment=uint64
Increment value for buckets (1)
-t, --threads=uint32
Number of threads (1)
-f,--full
Full histo. Don't skip count 0. (false)
-o, --output=string
Output file
-v,--verbose
Output information (false)
--usage
Usage
--help
This message
--full-help
Detailed help
-V,--version
Version
DUMP
Usage: jellyfish dump [options] db:path
Dump k-mer counts
By default, dump in a fasta format where the header is the count and the sequence is the sequence of the
k-mer. The column format is a 2 column output: k-mer count.
Options (default value in (), *required):
-c,--column
Column format (false)
-t,--tab
Tab separator (false)
-L, --lower-count=uint64
Don't output k-mer with count < lower-count
-U, --upper-count=uint64
Don't output k-mer with count > upper-count
-o, --output=string
Output file
--usage
Usage
-h,--help
This message
-V,--version
Version
MERGE
Usage: jellyfish merge [options] input:string+
Merge jellyfish databases
Options (default value in (), *required):
-s, --buffer-size=Buffer
length Length in bytes of input buffer (10000000)
-o, --output=string
Output file (mer_counts_merged.jf)
--out-counter-len=uint32
Length (in bytes) of counting field in output (4)
--out-buffer-size=uint64
Size of output buffer per thread (10000000)
-v,--verbose
Be verbose (false)
--usage
Usage
-h,--help
This message
-V,--version
Version
QUERY
Usage: jellyfish query [options] db:path
Query from a compacted database
Query a hash. It reads k-mers from the standard input and write the counts on the standard output.
Options (default value in (), *required):
-C,--both-strands
Both strands (false)
-c,--cary-bit
Value field as the cary bit information (false)
-i, --input=file
Input file
-o, --output=file
Output file
--usage
Usage
-h,--help
This message
-V,--version
Version
QHISTO
Usage: jellyfish qhisto [options] db:string
Create an histogram of k-mer occurences
Options (default value in (), *required):
-l, --low=double
Low count value of histogram (0.0)
-h, --high=double
High count value of histogram (10000.0)
-i, --increment=double
Increment value for buckets (1.0)
-f,--full
Full histo. Don't skip count 0. (false)
--usage
Usage
--help
This message
-V,--version
Version
QDUMP
Usage: jellyfish qdump [options] db:path
Dump k-mer from a qmer database
By default, dump in a fasta format where the header is the count and the sequence is the sequence of the
k-mer. The column format is a 2 column output: k-mer count.
Options (default value in (), *required):
-c,--column
Column format (false)
-t,--tab
Tab separator (false)
-L, --lower-count=double
Don't output k-mer with count < lower-count
-U, --upper-count=double
Don't output k-mer with count > upper-count
-v,--verbose
Be verbose (false)
-o, --output=string
Output file
--usage
Usage
-h,--help
This message
-V,--version
Version
QMERGE
Usage: jellyfish merge [options] db:string+
Merge quake databases
Options (default value in (), *required):
-s, --size=uint64
*Merged hash table size
-m, --mer-len=uint32
*Mer length
-o, --output=string
Output file (merged.jf)
-p, --reprobes=uint32
Maximum number of reprobes (62)
--usage
Usage
-h,--help
This message
--full-help
Detailed help
-V,--version
Version
CITE
Usage: jellyfish cite [options]
How to cite Jellyfish's paper
Citation of paper
Options (default value in (), *required):
-b,--bibtex
Bibtex format (false)
-o, --output=string
Output file
--usage
Usage
-h,--help
This message
-V,--version
Version
VERSION
Version: 1.1.4 of 2010/10/1
BUGS
* jellyfish merge has not been parallelized and is relatively slow.
* The hash table does not grow in memory automatically and jellyfish merge is not called
automatically on the intermediary files (if any).
COPYRIGHT & LICENSE
Copyright
(C)2010, Guillaume Marcais guillaume@marcais.net and Carl Kingsford carlk@umiacs.umd.edu.
License
This program is free software: you can redistribute it and/or modify it under the terms of the GNU
General Public License as published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not,
see http://www.gnu.org/licenses/.
AUTHORS
Guillaume Marcais
University of Maryland
gmarcais@umd.edu
Carl Kingsford
University of Maryland
carlk@umiacs.umd.edu