Kaldi nnet3 Upgrade Rollback: Restoring Original Training Scripts After a Failed Build

Goal

Recover a clean Kaldi environment after an unsuccessful upgrade of the nnet3 training scripts, preserving all existing data and model files.

Context & Constraints

The upgrade was performed from Kaldi 4.2 to 4.3. The build process terminated with a non‑fatal error, leaving the src directory partially updated. All training data and pre‑trained models in data and exp must remain untouched. The repository’s Makefile and configuration files now reference newer compiler flags that are incompatible with the old binary.

Unresolved Questions

• Which git operations can safely revert the src tree to the last working commit while leaving the data directories intact?
• What is the minimal set of configuration files that need to be restored to match the 4.2 build system?
• How can we verify that the old binaries and model files are still executable against the reverted source?