Biowulf High Performance Computing at the NIH
SGA-ICE on Biowulf

Iterative error correction of long 250 or 300 bp Illumina reads minimizes the total amount of erroneous reads, which improves contig assembly. This pipeline runs multiple rounds of k-mer-based correction with an increasing k-mer size, followed by a final round of overlap-based correction. By combining the advantages of small and large k-mers, this pipeline is able to correct more base substitution errors, especially in repeats. The final overlap-based correction round can also correct small insertions and deletions.


Important Notes

Interactive job
Interactive jobs should be used for debugging, graphics, or applications that cannot be run as batch jobs.

Allocate an interactive session and run the program. Sample session:

[user@biowulf]$ sinteractive -c 8 --mem=20g 
salloc.exe: Pending job allocation 46116226
salloc.exe: job 46116226 queued and waiting for resources
salloc.exe: job 46116226 has been allocated resources
salloc.exe: Granted job allocation 46116226
salloc.exe: Waiting for resource configuration
salloc.exe: Nodes cn3144 are ready for job

[user@cn3144 ~]$ module load SGA-ICE

[user@cn3144 ~]$ cd /scratch/$USER

[user@cn3144 ~]$ cp -r /usr/local/apps/SGA-ICE/TEST_DATA .

[user@cn3144 ~]$ /scratch/$USER/TEST_DATA -k 40,60,100,125,150,200 -t 8 --noCleanup --noOvlCorr --scriptName
### Input directory is: TEST_DATA/
### Number of threads is: 8
### User provided k-mers are: [40, 60, 100, 125, 150, 200]
### User chose not to do overlap correction
### Temporary files will not be deleted
### Error rate for sga correct 0.01
### Minimum overlap for sga correct 40
Shell script is called:
### These are the fastq files found in /spin1/scratch/teacher/TEST_DATA/:
### Your reads are 301 bp long, calculated from file: /spin1/scratch/teacher/TEST_DATA/SRR6219624_1.fastq

To run 6 correction round with k=40,60,100,125,150,200 using 8 threads, execute 

[user@cn3144 ~]$ cd TEST_DATA

[user@cn3144 ~]$ ./
Temporary directory is: /tmp/tmp.K1DyIAaV1g
### Start sga preprocessing ###
preprocess: WARNING - it is suggested that the min read length is 40
preprocess: Using very short reads may considerably impact the performance
QualTrim: 0
QualFilter: no filtering
HardClip: 0
Min length: 0
Sample freq: 1
PE Mode: 0
Quality scaling: 2
MinGC: 0
MaxGC: 1
Outfile: SRR6219624_1.SGAICEpreproc.fastq
Orphan file: none
Seed: 1527619454
Processing SRR6219624_1.fastq

[user@cn3144 ~]$ exit
salloc.exe: Relinquishing job allocation 46116226
[user@biowulf ~]$

Batch job
Most jobs should be run as batch jobs.

Create a batch input file (e.g. For example:

module load SGA-ICE

cd /scratch/teacher
cp -r /usr/local/apps/SGA-ICE/TEST_DATA . TEST_DATA -k 40,60,100,125,150,200 -t $SLURM_CPUS_PER_TASK --noCleanup --noOvlCorr --scriptName

Submit this job using the Slurm sbatch command.

sbatch --cpus-per-task=8 --mem=20g
Swarm of Jobs
A swarm of jobs is an easy way to submit a set of independent commands requiring identical resources.

Create a swarmfile (e.g. SGA-ICE.swarm). For example:

cd /dir/fastq/1; /dir/fastq/1 -t $SLURM_CPUS_PER_TASK [...]; ./ 
cd /dir/fastq/2; /dir/fastq/2 -t $SLURM_CPUS_PER_TASK [...]; ./
cd /dir/fastq/3; /dir/fastq/3 -t $SLURM_CPUS_PER_TASK [...]; ./

Submit this job using the swarm command.

swarm -f SGA-ICE.swarm -g 10 -t 8 --module SGA-ICE
-g # Number of Gigabytes of memory required for each process (1 line in the swarm command file)
-t # Number of threads/CPUs required for each process (1 line in the swarm command file).
--module SGA-ICE Loads the SGA-ICE module for each subjob in the swarm