This commit introduces entropy-based filtering for k-mers to remove low-complexity sequences. It adds:
- New KmerEntropy and KmerEntropyFilter functions in pkg/obikmer/entropy.go for computing and filtering k-mer entropy
- Integration of entropy filtering in the k-mer set builder (pkg/obikmer/kmer_set_builder.go)
- A new 'filter' command in obik tool (pkg/obitools/obik/filter.go) to apply entropy filtering on existing indices
- CLI options for configuring entropy filtering during index building and filtering
The entropy filter helps improve the quality of k-mer sets by removing repetitive sequences that may interfere with downstream analyses.
This commit introduces sparse index support for KDI files to enable fast random access during k-mer matching. It adds a new .kdx index file format and updates the KDI reader and writer to handle index creation and seeking. The changes include:
- New KdxIndex struct and related functions for loading, searching, and writing .kdx files
- Modified KdiReader to support seeking with the new index
- Updated KdiWriter to create .kdx index files during writing
- Enhanced KmerSetGroup.Contains to use the new index for faster lookups
- Added a new 'match' command to annotate sequences with k-mer match positions
The index is created automatically during KDI file creation and allows for O(log N / stride) binary search followed by at most stride linear scan steps, significantly improving performance for large datasets.
This commit introduces max frequency filtering to limit k-mer occurrences and adds functionality to save the N most frequent k-mers per set to CSV files. It also includes the ability to output k-mer frequency spectra as CSV and updates the CLI options accordingly.
This commit refactors the k-mer index management tools to use a unified subcommand structure with obik, adds support for per-set metadata and ID management, enhances the k-mer set group builder to support appending to existing groups, and improves command-line option handling with a new global options registration system.
Key changes:
- Introduce obik command with subcommands (index, ls, summary, cp, mv, rm, super, lowmask)
- Add support for per-set metadata and ID management in kmer set groups
- Implement ability to append to existing kmer index groups
- Refactor option parsing to use a global options registration system
- Add new commands for listing, copying, moving, and removing sets
- Enhance low-complexity masking with new options and output formats
- Improve kmer index summary with Jaccard distance matrix support
- Remove deprecated obikindex and obisuperkmer commands
- Update build process to use the new subcommand structure
Refactor k-mer index building to use the new disk-based KmerSetGroupBuilder instead of the old KmerSet and FrequencyFilter approaches. This change introduces a more efficient and scalable approach to building k-mer indices by using partitioned disk storage with streaming operations.
- Replace BuildKmerIndex and BuildFrequencyFilterIndex with KmerSetGroupBuilder
- Add support for frequency filtering via WithMinFrequency option
- Remove deprecated k-mer set persistence methods
- Update CLI to use new builder approach
- Add new disk-based k-mer operations (union, intersect, difference, quorum)
- Introduce KDI (K-mer Delta Index) file format for efficient storage
- Add K-way merge operations for combining sorted k-mer streams
- Update documentation and examples to reflect new API
This refactoring provides better memory usage, faster operations on large datasets, and more flexible k-mer set operations.
