EqualityConstraint¶
- class torch.fx.experimental.symbolic_shapes.EqualityConstraint(warn_only, source_pairs, derived_equalities, phantom_symbols)[source]¶
Represent and decide various kinds of equality constraints between input sources.
A “source pair” is a pair of input sources for dynamic dimensions that are specified equal. We represent source_pairs in a union-find forest so that we can efficiently check whether two such sources are transitively equal.
A “derived equality” relates an input source to an expression over a root. The root can be another input source, corresponding to some dynamic dimension, or a phantom symbol that does not directly represent any dynamic dimension. We represent derived_equalities involving input sources in a transitively-closed map so that we can efficiently check whether an input source is transitively equal to a given expression over another input source. (NOTE: In contrast, it is easy to decide whether an input source is transitively equal to a given expression over a phantom symbol; such expressions are already in canonical form and so the problem reduces to symbolic expression equality.)
