v0.38.4

DynamicPPL v0.38.4

Diff since v0.38.3

Improve performance of VarNamedVector. It should now be very nearly on par with Metadata for all models we've benchmarked on.

Merged pull requests:

• Improvements to VarNamedVector (#1098) (@mhauru)
• Print out intermediate benchmark results (#1100) (@mhauru)