bw2calc.least_squares

Module Contents

Classes

LeastSquaresLCA

Solve overdetermined technosphere matrix with more products than activities using least-squares approximation.

class bw2calc.least_squares.LeastSquaresLCA(demand: dict, method: tuple | None = None, weighting: str | None = None, normalization: str | None = None, data_objs: Iterable[pathlib.Path | fs.base.FS | bw_processing.DatapackageBase] | None = None, remapping_dicts: Iterable[dict] | None = None, log_config: dict | None = None, seed_override: int | None = None, use_arrays: bool | None = False, use_distributions: bool | None = False, selective_use: dict | None = False)

Bases: bw2calc.lca.LCA

Solve overdetermined technosphere matrix with more products than activities using least-squares approximation.

See also:

• Multioutput processes in LCA

• LSMR in SciPy

• Another least-squares algorithm in SciPy

Create a new LCA calculation object.

Compatible with Brightway2 and 2.5 semantics. Can be static, stochastic, or iterative (scenario-based), depending on the data_objs input data..

This class supports both stochastic and static LCA, and can use a variety of ways to describe uncertainty. The input flags use_arrays and use_distributions control some of this stochastic behaviour. See the [documentation for matrix_utils](brightway-lca/matrix_utils) for more information on the technical implementation.

Parameters

demanddict[object: float]

The demand for which the LCA will be calculated. The keys can be Brightway Node instances, (database, code) tuples, or integer ids.

methodtuple

Tuple defining the LCIA method, such as (‘foo’, ‘bar’). Only needed if not passing data_objs.

weightingtuple

Tuple defining the LCIA weighting, such as (‘foo’, ‘bar’). Only needed if not passing data_objs.

weightingstring

String defining the LCIA normalization, such as ‘foo’. Only needed if not passing data_objs.

data_objslist[bw_processing.Datapackage]

List of bw_processing.Datapackage objects. Can be loaded via bw2data.prepare_lca_inputs or constructed manually. Should include data for all needed matrices.

remapping_dictsdict[str, dict]

Dict of remapping dictionaries that link Brightway Node ids to (database, code) tuples. remapping_dicts can provide such remapping for any of activity, product, biosphere.

log_configdict

Optional arguments to pass to logging. Not yet implemented.

seed_overrideint

RNG seed to use in place of Datapackage seed, if any.

use_arraysbool

Use arrays instead of vectors from the given data_objs

use_distributionsbool

Use probability distributions from the given data_objs

selective_usedict[str, dict]

Dictionary that gives more control on whether use_arrays or use_distributions should be used. Has the form {matrix_label: {“use_arrays”|”use_distributions”: bool}. Standard matrix labels are technosphere_matrix, biosphere_matrix, and characterization_matrix.

abstract decompose_technosphere() → None

Factorize the technosphere matrix into lower and upper triangular matrices, \(A=LU\). Does not solve the linear system \(Ax=B\).

Doesn’t return anything, but creates self.solver.

Warning

Incorrect results could occur if a technosphere matrix was

factorized, and then a new technosphere matrix was constructed, as self.solver would still be the factorized older technosphere matrix. You are responsible for deleting self.solver when doing these types of advanced calculations.

load_lci_data() → None

Load inventory data and create technosphere and biosphere matrices.

solve_linear_system(solver=lsmr) → numpy.ndarray

Master solution function for linear system \(Ax=B\).

To most numerical analysts, matrix inversion is a sin.

—Nicolas Higham, Accuracy and Stability of Numerical Algorithms, Society for Industrial and Applied Mathematics, Philadelphia, PA, USA, 2002, p. 260.

We use pypardiso or UMFpack, which is a very fast solver for sparse matrices.

If the technosphere matrix has already been factorized, then the decomposed technosphere (self.solver) is reused. Otherwise the calculation is redone completely.