Spaced seed data structures
Bibliographic record
Abstract
This past decade, genome sciences have benefitted from rapid advances in DNA sequencing technologies, and development of efficient algorithms for processing short nucleotide sequences played a key role in enabling their uptake in the field. In particular, reassembly of human genomes (de novo or reference-guided) from short DNA sequence reads had a substantial impact on health research. De novo assembly of a genome is essential in the absence of a reference genome sequence of a species. It is also gaining traction even when one is available, due to the utility of the method to resolve ambiguous or rearranged genomic regions with high specificity. With commercial high-throughput sequencing technologies increasing their throughput and their read lengths, the de Bruijn graph (DBG) paradigm used by many assembly algorithms needs to be revisited. DBG uses a table of k-mers, sequences of length k base pairs derived from the reads, and their k-1 base pair overlaps to assemble sequences. Despite longer k-mers unlocking longer genomic features for assembly, associated increases in memory usage and other compute resources are tradeoffs that limit the practicability of DBG over other assembly archetypes already designed for longer reads. Here, we introduce three data structure designs for paired k-mers, or spaced seeds, each addressing memory and run time constraints imposed by longer reads. In spaced seeds, a fixed distance separates k-mer pairs, providing increased sequence specificity with increased distance, while keeping memory usage low. Further, we describe a data structure based on Bloom filters that would be suitable to implicitly store spaced seeds, and would be tolerant to sequencing errors. Building on the spaced seeds Bloom filter, we describe a data structure for tracking the frequencies of observed spaced seeds. We expect the data structure designs we introduce in this study to have broad applications in genomics research, with niche applications in genome, transcriptome and metagenome assemblies, and in read error correction.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.010 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.004 | 0.007 |
| Open science | 0.004 | 0.004 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.019 | 0.009 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".