Length of the sequence affects to runtime

[BiotechPedro]

Hi!

Why would grepq takes longer when "grepqing" a single N according to the length of the sequences?

time grepq --read-gzip N.txt DNA_R1.fastq.gz -c outputs:

237844016

real	0m25.290s
user	0m55.951s
sys	0m1.247s

but,

time grepq --read-gzip N.txt DNA_R2.fastq.gz -c outputs:

237844016

real	1m7.055s
user	1m25.311s
sys	0m3.354s

The lengths each read are {39, 18, 1 18} for DNA_R1.fastq.gz, and {39, 74, 1, 74} for DNA_R2.fastq.gz. If it is helpful, I am allocated in a node with 5 CPUs and 15G of memory.

Thanks,
Pedro