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40 lines
1.8 KiB
Markdown
40 lines
1.8 KiB
Markdown
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# Semantic Description of `obikmer` Package Functionalities
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The `obikmer` package provides tools for **super k-mer extraction and minimizer-based sequence analysis** in bioinformatics.
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## Core Concepts
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A **super k-mer** is a maximal contiguous subsequence of DNA where *all* embedded *k*-mers share the **same minimizer**—a compact representative (typically lexicographically minimal) of *m*-mers, considering both forward and reverse-complement strands.
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## Key Functions & Features
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- **`IterSuperKmers(seq, k, m)`**:
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An iterator over all super *k*-mers in input sequence `seq`, parameterized by:
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- `k`: length of embedded *k*-mers,
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- `m`: size of minimizer window (`m ≤ k`).
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Yields structured objects with:
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- `Sequence`: the super *k*-mer substring,
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- `Start`/`End`: genomic coordinates (0-based half-open),
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- `Minimizer`: canonical hash of the shared minimizer.
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- **`ExtractSuperKmers(...)`**:
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Synchronous counterpart returning a slice of all super *k*-mers.
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## Verified Properties (via Tests)
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1. **Boundary correctness**: Extracted subsequences match `seq[start:end]`.
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2. **Consistency between iterator and slice versions**: Both APIs produce identical results.
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3. **Bijection property**:
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- Each unique super *k*-mer sequence maps to exactly one minimizer.
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- All embedded *k*-mers within a super *k-mer* share the same minimizer.
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## Implementation Notes
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- Minimizers are computed canonically (min of forward and reverse-complement encodings).
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- Uses base encoding via `__single_base_code__` (assumed helper mapping A/C/G/T → 0/1/2/3).
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- Tests cover simple, homopolymer-rich, and complex genomic patterns.
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## Design Rationale
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Super *k*-mers enable efficient compression, indexing (e.g., in minimizer spaces), and alignment-free comparisons—crucial for scalable genomic analysis.
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