evomo.algorithms.grea#

Attributes#

algo

Classes#

GrEA

Initialize the GrEA population and optimization state.

Module Contents#

class evomo.algorithms.grea.GrEA(pop_size: int, n_objs: int, lb: torch.Tensor, ub: torch.Tensor, div: int | None = None, **kwargs)#

Bases: evox.core.Algorithm

Initialize the GrEA population and optimization state.

Parameters:

  • pop_size (int) – Required. Requested number of candidate solutions. Use a positive integer; algorithm-specific minimums and reference-vector sampling are described below.

  • n_objs (int) – Required. Number of objectives, matching the second dimension of the problem’s objective tensor. Objectives are minimized; this library targets two or more objectives.

  • lb (torch.Tensor) – Required. Lower decision bounds of shape (D,), where D is the number of decision variables. Use floating-point bounds with the same shape, dtype and device as ub, and lb <= ub elementwise.

  • ub (torch.Tensor) – Required. Upper decision bounds of shape (D,). The decision dimension is inferred from the bounds, rather than passed separately. Match lb in shape, dtype and device.

  • div (int) – Default: None. Positive number of grid divisions per objective. More divisions give finer objective-space cells; grid occupancy or grid distance is used during selection. None uses the setting recommended for the number of objectives (45, 15, 10, 9, 9, 8, 8, 10, 12 for 2 to 10 objectives, as in PlatEMO).

  • kwargs (dict) – Default: {}. Extra keyword arguments are accepted for constructor compatibility but are not read by this implementation. In particular, passing device=... here does not move tensors; place both bounds on the intended device before construction.

Note

Use this algorithm through a workflow that connects the problem’s evaluation method. Call workflow.init_step() before workflow.step() or compiling the step. The current evaluation path expects an objective tensor of shape (B, n_objs). It does not consume a (fitness, constraint_violation) tuple.

Tensor allocation uses lb.device. There is no explicit device parameter; prepare both bounds on the intended device.

init_step() → None#

Evaluate the initial population and initialize algorithm state.

Invoke through workflow.init_step() before the first optimization step.

Returns:

None; results are stored in algorithm state.

step() → None#

Advance optimization and update population and fitness state in place.

Invoke through workflow.step() after initialization. The caller controls termination.

Returns:

None; results are stored in algorithm state.

evomo.algorithms.grea.algo#