DimDynamic

class torch.fx.experimental.symbolic_shapes.DimDynamic(value)

Controls how to perform symbol allocation for a dimension. It is always sound to default this to DYNAMIC, but the policies DUCK and STATIC can result in better trace-time and compile-time performance, as they reduce the number of allocated symbols and generally make your graph more static.

NB: If we notice you’ve applied a constraint to the dimension, we will force it to DYNAMIC for simplicity.

DimDynamic is controlled by a variety of higher level UX features. Currently:

• In eager mode, the default policy is DUCK.

  • The default is changed to STATIC with assume_static_by_default.

  • An individual dim is marked DYNAMIC if you mark_dynamic_dim.

• In export mode, the default policy is STATIC.

  • An individual dim is marked DYNAMIC if you mention it as dynamic_dim in the constraints kwarg.