Canu Parameter Reference（canu参数介绍）

To get the most up-to-date options, run

canu -options

The default values below will vary based on the input data type and genome size.(根据输入数据类型和基因组大小决定默认参数)

Global Options （全局参数）

The catch all category.

errorRate <float=0.01>: The expected error rate, as fraction error分数形式, in the corrected reads, set by default based on data type, typically not changed by the user.
genomeSize <float=unset>: An estimate of the size of the genome估计的基因组大小. Common suffices are allowed, for example, 3.7m or 2.8g. Required.
canuIteration <internal parameter, do not use>: Which parallel iteration并行迭代 is being attempted.
canuIterationMax <integer=2>: How many parallel iterations to try. Ideally, the parallel jobs, run under grid control, would all finish successfully on the first try. Sometimes, jobs fail due to other jobs exhausting resources (memory), or by the node itself failing. In this case, canu will launch the jobs again. This parameter controls how many times it tries.

Process Control 流程控制

showNext <boolean=false>

Report the first major command that would be run, but don’t run it. Processing to get to that command, for example, checking the output of the previous command or preparing inputs for the next command, is still performed.

stopBefore <string=undefined>

Stop processing just before this stage would execute. The stage is configured, and the command logged to the standard output, before stopping. For grid-based stages, e.g., overlapper, the grid submit command is reported.

If the stage has finished successfully, it will not stop.

Only one stage may be supplied to stopBefore.

Valid stages to stopBefore are:

gatekeeper
meryl
overlap
correction
overlapErrorAdjustment
trimReads
splitReads
unitig
consensusConfigure
consensus
output

The default value is ‘undef’.

stopAfter <string=undefined>

Stop processing after this stage completes.

The stage will typically stop BEFORE a summary of its processing is reported in the canu chatter.

Valid stages top stopAfter are:

gatekeeper
meryl
overlapConfigure
overlap
correction
unitig
consensusConfigure
consensus
consensusLoad
consensusFilter

General Options 通用选项

pathMap <string=undefined>

A text file containing lines that map a hostname to a path to the assembler binaries. This can be used to provide fine-grained binary directories, for example, when incompatible versions of the operating system are used, or when canu is installed in a non-standard way.

The hostname must be the same as returned by ‘uname -n’. For example:

grid01   /grid/software/canu/Linux-amd64/bin/

devel01  /devel/canu/Linux-amd64/bin/

shell <string=”/bin/sh”>

A path to a Bourne shell, to be used for executing scripts. By default, ‘/bin/sh’, which is typically the same as ‘bash’. C shells (csh, tcsh) are not supported.

java <string=”java”>

A path to a Java application launcher of at least version 1.8.

Cleanup Options 清除选项

saveOverlaps <boolean=false>

If set, do not remove raw overlap output from either mhap or overlapInCore. Normally, this output is removed once the overlaps are loaded into an overlap store.

saveReadCorrections <boolean=false.

If set, do not remove raw corrected read output from correction/2-correction. Normally, this output is removed once the corrected reads are generated.

saveIntermediates <boolean=false>

If set, do not remove intermediate outputs. Normally, intermediate files are removed once they are no longer needed.

NOT IMPLEMENTED.

saveMerCounts <boolean=false>

If set, do not remove meryl binary databases.

Overlapper Configuration 设置

Overlaps are generated for three purposes: read correction, read trimming and unitig construction. The algorithm and parameters used can be set independently for each set of overlaps.

Two overlap algorithms are in use. One, mhap, is typically applied to raw uncorrected reads and returns alignment-free overlaps with imprecise extents. The other, the original overlapper algorithm ‘ovl’, returns alignments but is much more expensive.

There are three sets of parameters, one for the ‘mhap’ algorithm, one for the ‘ovl’ algorithm, and one for the ‘minimap’ algorithm. Parameters used for a specific type of overlap are set by a prefix on the option: ‘cor’ for read correction, ‘obt’ for read trimming (‘overlap based trimming’) or ‘utg’ for unitig construction. For example, ‘corOverlapper=ovl’ would set the overlapper used for read correction to the ‘ovl’ algorithm.

{prefix}Overlapper <string=see-below>: Specify which overlap algorith, ‘mhap’ or ‘ovl’ or ‘minimap’. The default is to use ‘mhap’ for ‘cor’ and ‘ovl’ for both ‘obt’ and ‘utg’.

Overlapper Configuration, ovl Algorithm

{prefix}OvlErrorRate <float=unset>: Overlaps above this error rate are not computed.
{prefix}OvlFrequentMers <string=undefined>: Do not seed overlaps with these kmers (fasta format).
{prefix}OvlHashBits <integer=unset>: Width of the kmer hash. Width 22=1gb, 23=2gb, 24=4gb, 25=8gb. Plus 10b per corOvlHashBlockLength.
{prefix}OvlHashBlockLength <integer=unset>: Amount of sequence (bp to load into the overlap hash table.
{prefix}OvlHashLoad <integer=unset>: Maximum hash table load. If set too high, table lookups are inefficent; if too low, search overhead dominates run time.
{prefix}OvlMerDistinct <integer=unset>: K-mer frequency threshold; the least frequent fraction of distinct mers can seed overlaps.
{prefix}OvlMerSize <integer=unset>: K-mer size for seeds in overlaps.
{prefix}OvlMerThreshold <integer=unset>: K-mer frequency threshold; mers more frequent than this count are not used to seed overlaps.
{prefix}OvlMerTotal <integer=unset>: K-mer frequency threshold; the least frequent fraction of all mers can seed overlaps.
{prefix}OvlRefBlockLength <integer=unset>: Amount of sequence (bp to search against the hash table per batch.
{prefix}OvlRefBlockSize <integer=unset>: Number of reads to search against the hash table per batch.

Overlapper Configuration, mhap Algorithm

{prefix}MhapBlockSize <integer=unset>: Number of reads per 1GB block. Memory * size is loaded into memory per job.
{prefix}MhapMerSize <integer=unset>: K-mer size for seeds in mhap.
{prefix}ReAlign <boolean=false>: Compute actual alignments from mhap overlaps; ‘raw’ from mhap output; uses either obtErrorRate or ovlErrorRate, depending on which overlaps are computed)
{prefix}MhapSensitivity <string=”normal”>: Coarse sensitivity level: ‘normal’ or ‘high’ or ‘fast’.

Overlapper Configuration, mhap Algorithm

{prefix}MMapBlockSize <integer=unset>: Number of reads per 1GB block. Memory * size is loaded into memory per job.
{prefix}MMapMerSize <integer=unset>: K-mer size for seeds in minimap.
{prefix}ReAlign <boolean=false>: Compute actual alignments from minimap overlaps; ‘raw’ from mhap output; uses either obtErrorRate or ovlErrorRate, depending on which overlaps are computed)

Overlap Store 保存

The overlap algorithms return overlaps in an arbitrary order. The correction, trimming and assembly algorithms usually need to know all overlaps for a single read. The overlap store duplicates each overlap, sorts them by the first ID, and stores them for quick retrieval of all overlaps for a single read.

ovsMemory <integer=2>: How much memory, in gigabytes, to use for constructing overlap stores.
ovsMethod <string=”sequential”>: Two construction algorithms are supported. One uses a single data stream, and is faster for small and moderate size assemblies. The other uses parallel data streams and can be faster (depending on your network disk bandwitdh) for moderate and large assemblies.

Meryl

The ‘meryl’ algorithm counts the occurrences of kmers in the input reads. It outputs a FASTA format list of frequent kmers, and (optionally) a binary database of the counts for each kmer in the input.

Meryl can run in (almost) any memory size, by splitting the computation into smaller (or larger) chunks.

merylMemory <integer=unset>: Amount of memory, in gigabytes, to use for counting kmers.
merylThreads <integer=unset>: Number of compute threads to use for kmer counting.

Overlap Based Trimming基于overlap的修剪

obtErrorRate <float=unset>: Stringency of overlaps to use for trimming
trimReadsOverlap <integer=1>: Minimum overlap between evidence to make contiguous trim.
trimReadsCoverage <integer=1>: Minimum depth of evidence to retain bases.

Grid Engine Support集群支持

Canu supports Sun/Open/Univa Grid Engine (SGE), Portable Batch System (PBS), Platform Computing’s Load Sharing Facility (LSF), and the Simple Linux Utility for Resource Management (SLURM). Most of the compute intensive stages can run under grid control.

The useGrid* options control which algorithms run in parallel on the grid.

useGrid <boolean=true>

Master control. If ‘false’, no algorithms will run under grid control. Does not change the value of the other useGrid options.

If ‘remote’, jobs are configured for grid execution, but not submitted. A message, with commands to launch the job, is reported and canu halts execution.

Note that the host used to run canu for ‘remote’ execution must know about the grid, that is, it must be able to submit jobs to the grid.

There are many options for configuring a new grid (‘gridEngine*’) and for configuring how canu configures its computes to run under grid control (‘gridOptions*’). The grid engine to use is specified with the ‘gridEngine’ option.

gridEngine <string>

Which grid engine to use. Auto-detected. Possible choices are ‘sge’, ‘pbs’, ‘lsf’ or ‘slurm’.

NOTE: ‘lsf’ support is untested.

Grid Engine Configuration

There are many options to configure support for a new grid engine, and we don’t describe them fully. If you feel the need to add support for a new engine, please contact us. That said, file src/pipeline/canu/Defaults.pm lists a whole slew of parameters that are used to build up grid commands, they all start with gridEngine. For each grid, these parameters are defined in the various src/pipeline/Grid_*.pm modules. The parameters are used in src/pipeline/canu/Execution.pm.

For SGE grids, two options are sometimes necessary to tell canu about pecularities of your grid: gridEngineThreadsOption describes how to request multiple cores, and gridEngineMemoryOption describes how to request memory. Usually, canu can figure out how to do this, but sometimes it reports an error such as:

-- WARNING:  Couldn't determine the SGE parallel environment to run multi-threaded codes.

--           Valid choices are (pick one and supply it to canu):

--             gridEngineThreadsOption="-pe make THREADS"

--             gridEngineThreadsOption="-pe make-dedicated THREADS"

--             gridEngineThreadsOption="-pe mpich-rr THREADS"

--             gridEngineThreadsOption="-pe openmpi-fill THREADS"

--             gridEngineThreadsOption="-pe smp THREADS"

--             gridEngineThreadsOption="-pe thread THREADS"

or:

-- WARNING:  Couldn't determine the SGE resource to request memory.

--           Valid choices are (pick one and supply it to canu):

--             gridEngineMemoryOption="-l h_vmem=MEMORY"

--             gridEngineMemoryOption="-l mem_free=MEMORY"

If you get such a message, just add the appropriate line to your canu command line. Both options will replace the uppercase text (THREADS or MEMORY) with the value canu wants when the job is submitted. For gridEngineMemoryOption, any number of -l options can be supplied; we could use gridEngineMemoryOption="-l h_vmem=MEMORY -l mem_free=MEMORY" to request both h_vmem and mem_free memory.

Grid Options

To run on the grid, each stage needs to be configured - to tell the grid how many cores it will use and how much memory it needs. Some support for this is automagic (for example, overlapInCore and mhap know how to do this), others need to be manually configured. Yes, it’s a problem, and yes, we want to fix it.

The gridOptions* parameters supply grid-specific opitons to the grid submission command.

gridOptions <string=unset>: Grid submission command options applied to all grid jobs
gridOptionsJobName <string=unset>: Grid submission command jobs name suffix
gridOptionsCNS <string=unset>: Grid submission command options applied to unitig consensus jobs
gridOptionsCOR <string=unset>: Grid submission command options applied to read correction jobs
gridOptionsExecutive <string=unset>: Grid submission command options applied to master script jobs
gridOptionsOEA <string=unset>: Grid submission command options applied to overlap error adjustment jobs
gridOptionsRED <string=unset>: Grid submission command options applied to read error detection jobs
gridOptionsOVB <string=unset>: Grid submission command options applied to overlap store bucketizing jobs
gridOptionsOVS <string=unset>: Grid submission command options applied to overlap store sorting jobs
gridOptionsCORMHAP <string=unset>: Grid submission command options applied to mhap overlaps for correction jobs
gridOptionsCOROVL <string=unset>: Grid submission command options applied to overlaps for correction jobs
gridOptionsOBTMHAP <string=unset>: Grid submission command options applied to mhap overlaps for trimming jobs
gridOptionsOBTOVL <string=unset>: Grid submission command options applied to overlaps for trimming jobs
gridOptionsUTGMHAP <string=unset>: Grid submission command options applied to mhap overlaps for unitig construction jobs
gridOptionsUTGOVL <string=unset>: Grid submission command options applied to overlaps for unitig construction jobs

Algorithm Selection 算法选项

Several algorithmic components of canu can be disabled, based on the type of the reads being assebmled, the type of processing desired, or the amount of comput resources available. Overlap

enableOEA <boolean=true>: Do overlap error adjustment - comprises two steps: read error detection (RED and overlap error adjustment (OEA

WHERE IS OBT??

Algorithm Execution Method

Each of the high compute stages can be computed either on a grid or in parallel on the local machine. Most algorithms will respect a given maximum memory usage. Most algorithms can support more than a single thread of computation. When the grid engine is not used, more than one task can be run at a time.

BUG: Local execution doesn’t pay attention to memory option.

For execution locally, three parameters describe the task:

{prefix}Concurrency <integer=unset>: Set the number of tasks that can run at the same time, when running without grid support.

Available prefixes are:

{prefix}Threads <integer=unset>: Set the number of compute threads used per task.

Available prefixes are:

{prefix}Memory <integer=unset>: Set the amount of memory, in GB, to use for each job in a task.

Available prefixes are:

master
bat
ovb
ovs
cns
cor
cormhap
obtmhap
utgmhap
corovl
obtovl
utgovl
cormmap
obtmmap
utgmmap
red
oea

Overlap Error Adjustment误差调整

red = Read Error Detection oea = Overlap Error Adjustment

oeaBatchLength <unset>: Number of bases per overlap error correction batch
oeaBatchSize <unset>: Number of reads per overlap error correction batch
redBatchLength <unset>: Number of bases per fragment error detection batch
redBatchSize <unset>: Number of reads per fragment error detection batch

Unitigger

unitigger <string=”bogart”>: Which unitig construction algorithm to use. Only “bogart” is supported.
batOptions <unset>: Advanced options to bogart

Consensus Partitioning 一致性

STILL DONE BY UNITIGGER, NEED TO MOVE OUTSIDE

cnsConsensus: Which algorithm to use for computing consensus sequences. Only ‘utgcns’ is supported.
cnsPartitions: Compute conseus by splitting the tigs into N partitions.
cnsPartitionMin: Don’t make a paritition with fewer than N reads
cnsMaxCoverage: Limit unitig consensus to at most this coverage.
cnsErrorRate: Possibly unused.

Read Correction 校正

The first step in Canu is to find high-error overlaps and generate corrected sequences for subsequent assembly. This is currently the fastest step in Canu. By default, only the longest 40X of data (based on the specified genome size) is used for correction. Typically, some reads are trimmed during correction due to being chimeric or having erroneous sequence, resulting in a loss of 20-25% (30X output). You can force correction to be non-lossy by setting

corMinCoverage=0

In which case the corrected reads output will be the same length as the input data, keeping any high-error unsupported bases. Canu will trim these in downstream steps before assembly.

If you have a dataset with uneven coverage or small plasmids, correcting the longest 40X may not give you sufficient coverage of your genome/plasmid. In these cases, you can set

corOutCoverage=400

Or any large value greater than your total input coverage which will correct and assemble all input data, at the expense of runtime.

corConsensus <string=”falconpipe”>: Which algorithm to use for computing read consensus sequences. Only ‘falcon’ and ‘falconpipe’ are supported.
corPartitions <integer=128>: Partition read correction into N jobs
corPartitionMin <integer=25000>: Don’t make a read correction partition with fewer than N reads
corMinEvidenceLength <integer=unset>: Limit read correction to only overlaps longer than this; default: unlimited
corMinCoverage <integer=4>: Limit read correction to regions with at least this minimum coverage. Split reads when coverage drops below threshold.
corMaxEvidenceErate <integer=unset>: Limit read correction to only overlaps at or below this fraction error; default: unlimited
corMaxEvidenceCoverageGlobal <string=”1.0x”>: Limit reads used for correction to supporting at most this coverage; default: 1.0 * estimated coverage
corMaxEvidenceCoverageLocal <string=”2.0x”>: Limit reads being corrected to at most this much evidence coverage; default: 10 * estimated coverage
corOutCoverage <integer=40>: Only correct the longest reads up to this coverage; default 40
corFilter <string=”expensive”>: Method to filter short reads from correction; ‘quick’ or ‘expensive’ or ‘none’
falconSense: Path to fc_consensus.py or falcon_sense.bin

Output Filtering 输出过滤

By default, canu will split the final output into three files:

asm.contigs.fasta: Everything which could be assembled and is part of the primary assembly, including both unique and repetitive elements. Each contig has several flags included on the fasta def line:
asm.bubbles.fasta: alternate paths in the graph which could not be merged into the primary assembly.
asm.unassembled.fasta: reads/tigs which could not be incorporated into the primary or bubble assemblies.

It is possible for tigs comprised of multiple reads to end up in asm.unassembled.fasta. The default filtering eliminates anything with < 2 reads, shorter than 1000bp, or comprised of mostly a single sequence (>75%). The filtering is controlled by the contigFilter parameter which takes 5 values.

contigFilter

  minReads

  minLength

  singleReadSpan

  lowCovSpan

  lowCovDepth

The default filtering is “2 1000 0.75 0.75 2”. If you are assembling amplified data or viral data, it is possible your assembly will be flagged as unassembled. In those cases, you can turn off the filtering with the parameters

contigFilter="2 1000 1.0 1.0 2"