HWpar

See also the lecture

Deadline: 22th May 2025 9:00

For both tasks, submit your source code and the result, when run on whole dataset (/tasks/par/dataset). The code is expected to use the Apache beam framework presented in the lecture. Submit directory is /submit/par/

Task A

Count the number of occurrences of each 4-mer in the provided data.

Provided data are in Fastq format. They contain reads from some genomic sequencing. By a read we mean part of some DNA. In Fastq format each read is on 4 lines. The first line starts with @ and contains the read name. The second line contains the actual read (this is the important part for you). The third line contains + and the read name again. The fourth line contains a quality score for each base (you should ignore this).

By k-mer we mean any consecutive substring in a read. For example, in a read "ACGGCTA" the 4-mers are: "ACGG", "CGGC", "GGCT", "GCTA".

Task B

Count the number of pairs of reads that overlap in exactly 30 bases (the end of one read overlaps the beginning of the second read). For bioinformaticians: You can ignore the reverse complement.

One more clarification: If you have two reads (and say we are counting 4 base overlaps): AAAAxxxxxCCCC and CCCCxxxxxAAAA, this counts as two overlaps.

Hints:

• Try counting pairs for each 30-mer first.
• You can yield something structured from Map/ParDo operatation (e.g. tuple).
• You can have another Map/ParDo after CombinePerKey.
• Run code on small data (subset of all files or even one file or even your small custom data) to quickly iterate and test :)