strategies
lacuna.batch.strategies
¶
Batch processing strategies for different analysis types.
This module implements the Strategy pattern for batch processing, enabling automatic optimization based on analysis characteristics:
- ParallelStrategy: Independent per-subject processing with multiprocessing
- VectorizedStrategy: Batch matrix operations for connectome analyses
BatchStrategy
¶
Bases: ABC
Abstract base class for batch processing strategies.
Each strategy implements a different approach to processing multiple subjects: - Parallel: Uses multiprocessing for independent analyses - Vectorized: Stacks data for batch matrix operations
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
n_jobs
|
int
|
Number of parallel jobs. -1 uses all available cores. Only relevant for ParallelStrategy. |
-1
|
Source code in src/lacuna/batch/strategies.py
name
abstractmethod
property
¶
Strategy name for logging and debugging.
execute(inputs, analysis, progress_callback=None)
abstractmethod
¶
Execute analysis on all lesions using this strategy.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
inputs
|
list[SubjectData]
|
List of lesions to process |
required |
analysis
|
BaseAnalysis
|
Analysis instance to apply to each lesion |
required |
progress_callback
|
callable or None
|
Optional callback function to report progress. Called with current index after each subject completes. |
None
|
Returns:
| Type | Description |
|---|---|
list[SubjectData]
|
List of processed SubjectData objects with results added |
Raises:
| Type | Description |
|---|---|
RuntimeError
|
If execution fails |
Source code in src/lacuna/batch/strategies.py
ParallelStrategy
¶
Bases: BatchStrategy
Parallel batch processing using joblib multiprocessing.
Best for independent per-subject analyses (RegionalDamage, ParcelAggregation) Speedup on multi-core systems (proportional to available cores) Low memory overhead
This strategy processes each subject independently using joblib.Parallel. The backend can be configured to handle different environments: - 'loky' (default): Robust multiprocessing for standalone scripts - 'threading': Thread-based parallelism for Jupyter notebooks - 'multiprocessing': Standard multiprocessing (less robust than loky)
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
n_jobs
|
int
|
Number of parallel jobs: - -1: Use all available CPU cores - 1: Sequential processing (useful for debugging) - N: Use N parallel workers |
-1
|
backend
|
str
|
Joblib backend to use: - 'loky': Robust multiprocessing (best for scripts) - 'threading': Thread-based (use in Jupyter notebooks) - 'multiprocessing': Standard multiprocessing |
'loky'
|
Examples:
>>> from lacuna.batch.strategies import ParallelStrategy
>>> from lacuna.analysis import RegionalDamage
>>>
>>> # For standalone scripts (default)
>>> strategy = ParallelStrategy(n_jobs=4)
>>> results = strategy.execute(lesions, RegionalDamage())
>>>
>>> # For Jupyter notebooks
>>> strategy = ParallelStrategy(n_jobs=4, backend='threading')
>>> results = strategy.execute(lesions, RegionalDamage())
Source code in src/lacuna/batch/strategies.py
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execute(inputs, analysis, progress_callback=None)
¶
Execute parallel batch processing.
Processes subjects in parallel using joblib. Each subject is processed independently, and failures are caught and reported as warnings without stopping the entire batch.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
inputs
|
list[SubjectData]
|
Subjects to process |
required |
analysis
|
BaseAnalysis
|
Analysis to apply |
required |
progress_callback
|
callable or None
|
Progress reporting function |
None
|
Returns:
| Type | Description |
|---|---|
list[SubjectData]
|
Successfully processed subjects (failures are filtered out) |
Source code in src/lacuna/batch/strategies.py
SequentialStrategy
¶
Bases: BatchStrategy
Sequential batch processing for analyses that should not run in parallel.
Best for analyses with external dependencies that don't benefit from parallel execution (e.g., StructuralNetworkMapping with MRtrix3).
This strategy processes each subject one at a time, regardless of the n_jobs parameter. It's designed for analyses where: - External tools handle their own internal parallelization (e.g., tckedit -nthreads) - Running multiple instances in parallel causes resource contention - Memory-mapped files or shared resources would conflict
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
n_jobs
|
int
|
Not used for sequential processing. Kept for interface compatibility. The analysis itself may use internal parallelization (e.g., MRtrix3's -nthreads). |
-1
|
Examples:
>>> from lacuna.batch.strategies import SequentialStrategy
>>> from lacuna.analysis import StructuralNetworkMapping
>>>
>>> strategy = SequentialStrategy()
>>> results = strategy.execute(masks, StructuralNetworkMapping(...))
Source code in src/lacuna/batch/strategies.py
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execute(inputs, analysis, progress_callback=None)
¶
Execute sequential batch processing.
Processes subjects one at a time. Failures are caught and reported as warnings without stopping the entire batch.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
inputs
|
list[SubjectData]
|
Subjects to process |
required |
analysis
|
BaseAnalysis
|
Analysis to apply |
required |
progress_callback
|
callable or None
|
Progress reporting function |
None
|
Returns:
| Type | Description |
|---|---|
list[SubjectData]
|
Successfully processed subjects (failures are filtered out) |
Source code in src/lacuna/batch/strategies.py
VectorizedStrategy
¶
Bases: BatchStrategy
Vectorized batch processing using batched NumPy operations.
Best for matrix-based analyses (FunctionalNetworkMapping) Speedup via optimized BLAS operations and reduced overhead Moderate memory overhead (processes lesions in configurable batches)
This strategy leverages vectorized operations to process multiple lesions simultaneously through each connectome batch. Instead of: for lesion in lesions: for connectome_batch in batches: process(lesion, connectome_batch)
It does: for connectome_batch in batches: process_all_lesions_together(lesions_batch, connectome_batch)
This dramatically reduces overhead and enables efficient BLAS operations.
The analysis class must implement: run_batch(inputs: list[SubjectData]) -> list[SubjectData]
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
n_jobs
|
int
|
Not used for vectorized processing (uses BLAS parallelization instead). Kept for interface compatibility. |
-1
|
lesion_batch_size
|
int or None
|
Number of lesions to process together in memory. - None: Process all lesions together (maximum speed, high memory) - N: Process N lesions at a time (balanced speed/memory) Useful when processing hundreds of lesions. |
None
|
Examples:
>>> from lacuna.batch.strategies import VectorizedStrategy
>>> from lacuna.analysis import FunctionalNetworkMapping
>>>
>>> # Process all lesions together (fastest)
>>> strategy = VectorizedStrategy()
>>> results = strategy.execute(lesions, FunctionalNetworkMapping(...))
>>>
>>> # Process 50 lesions at a time (memory-constrained)
>>> strategy = VectorizedStrategy(lesion_batch_size=50)
>>> results = strategy.execute(lesions, FunctionalNetworkMapping(...))
Source code in src/lacuna/batch/strategies.py
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execute(inputs, analysis, progress_callback=None)
¶
Execute vectorized batch processing.
Calls analysis.run_batch() which processes multiple lesions together using vectorized operations. Falls back to sequential processing if run_batch() is not implemented.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
inputs
|
list[SubjectData]
|
Subjects to process |
required |
analysis
|
BaseAnalysis
|
Analysis to apply (must implement run_batch method) |
required |
progress_callback
|
callable or None
|
Progress reporting function (called after each lesion batch) |
None
|
Returns:
| Type | Description |
|---|---|
list[SubjectData]
|
Processed subjects |
Raises:
| Type | Description |
|---|---|
NotImplementedError
|
If analysis doesn't implement run_batch() |
Source code in src/lacuna/batch/strategies.py
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